# Most Efficient Motor



## Automcdonough (Sep 1, 2010)

That's a lot of controller for such a wimpy motor. You think it would still hit 99% at only 25% load? I don't, typically best efficiency is at high load.

I also don't think that motor has enough gusto to be in-wheel without a gear reduction. Peak torque of only 50Nm (37ft-lb).
A typical motor pushing 100ft-lbs in 2nd gear can be about 1,000ft-lbs at the wheels.

Yes that gear reduction will mean a few moving parts, but it could be possible to package as in-wheel. Just that particular motor didn't.

I guess to be reasonable we could pancake 2 or 3 of them up where a different motor to compare it to would be. I think this could be less efficient than a single larger motor.

Sorry to be an ass about it. I assumed we are restricting this to being reasonable for auto use but you didn't actually say that.


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## IamIan (Mar 29, 2009)

Automcdonough said:


> That's a lot of controller for such a wimpy motor. You think it would still hit 99% at only 25% load? I don't, typically best efficiency is at high load.


You are correct... the trend does still hold.
At ~25% load or ~4 kw the Wavesculptor20 drops to ~98% Efficiency.
See page 7 of an example here:
http://www.tritium.com.au/products/TRI50/TRI50.016_Datasheet_v6.pdf

But compared to other motor controllers I don't know of other designs that are still about to pull off ~98% efficiency when only operating at ~25% Load.

So even though the real time efficiency definitely changes... The design still seems more efficient than others I have seen... even across a wide operating range.

But I am happy to see something better is anyone knows of something.



Automcdonough said:


> I also don't think that motor has enough gusto to be in-wheel without a gear reduction. Peak torque of only 50Nm (37ft-lb).


The link I found and posted was for a Solar Car version of the CSIRO motor which do not need the same kind of torque a full highway speed commuter car does.

But CSIRO does make more powerful motors as shown in the next link where Tritium is showing the Wavesculptor20 pared with a 12kw output CSIRO doing well over 100 Nm
http://www.tritium.com.au/products/TRI50/TRI50.019_Motor_Impedance_v1.pdf



Automcdonough said:


> I guess to be reasonable we could pancake 2 or 3 of them up where a different motor to compare it to would be. I think this could be less efficient than a single larger motor.


How much of a Efficiency hit do you think it would take from pancaking?
What high efficiency larger motor are you thinking of?



Automcdonough said:


> Sorry to be an ass about it. I assumed we are restricting this to being reasonable for auto use but you didn't actually say that.


I don't think you are being an ass at all... all good points thus far.

That 20kw Wavescultpor20 is easily able to operate a regular vehicle ... 20kw can push around NEV just fine ... or even a very light weight vehicle at highway cruising speeds ... although 20 kw would not accelerate very quickly in all but the lightest platforms.

If you had one for each of 4 wheels you could potentially be up to 80 kw and still have a ~99% efficient capable controller network.

I have not yet found detailed papers on the performance of scaling up the CSIRO design ... But I suspect it would still be an extremely efficient Electric Motor... even scaled up.... even if we got it scaled up into the 10kw to 20kw range it would be a nice size paring with the Wavescultpor20... and sense there is an example of a 12kw ... I just don't know what that efficiency curve looks like.

The Wavesculptor200 next link ... as allot more motor controler power but does suffer a little efficiency drop to ~97% instead of ~99%... but is still a very efficient design platform.
http://www.tritium.com.au/products/TRI74/index.html


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## samborambo (Aug 27, 2008)

For solar racing the BLDC motor would be perfect - predictable load.

Induction motors are typically more efficient across a wider speed / torque range compared to BLDC since they can be field weakened more easily. The 98% efficiency would probably be very hard to achieve on a BLDC in every day driving conditions.

So induction is probably a better choice for a practical EV. If you're intent is a wheel motor, have a look at axial induction motors.

Sam.


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## IamIan (Mar 29, 2009)

samborambo said:


> Induction motors are typically more efficient across a wider speed / torque range compared to BLDC since they can be field weakened more easily. The 98% efficiency would probably be very hard to achieve on a BLDC in every day driving conditions.


What induction motor are you thinking of?
Pared with what controller?

I am trying to figure out ... personal curiosity ... what is the most efficient combination ... that is actually available to buy is ... so if there is another combination that can do better ... please let me know what it is.

The point about peak efficiency vs net operating efficiency is a good one ... but not a guarantee .... this combination has a pretty good operating efficiency range.

Definitely agreed the peak efficiencies will not likely to be sustainable in real world driving ... and real world efficiencies will always be lower than the peak best case.

But with the BLDC controller only dropping from full load ~99% down to ~98% at 25% Load ... the Wavesculptor Controller is not loosing much over the operational range.

The BLDC motor will loose more than the BLDC controller ... but what motor and controller out there is good enough to squeak out a net higher efficiency? ... I don't know of one.

If anybody does ... please let me know.


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## Qer (May 7, 2008)

You DO realise, I hope, that chasing efficiency in the motor/controller will probably be, as we say in Sweden, to filter the mosquitoes but swallow the camels?

Your losses will be much higher in the battery pack and transmission plus that air resistance will probably be the single biggest energy loss there is, so chasing the last percent in the motor/controller shouldn't be considered until you've done your best to minimize all the other energy losses.


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## IamIan (Mar 29, 2009)

Qer said:


> You DO realise, I hope, that chasing efficiency in the motor/controller will probably be, as we say in Sweden, to filter the mosquitoes but swallow the camels?


Yes.

Still , I remain curious if there is a more efficient combination of motor and controller that is available to purchase.


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## sunworksco (Sep 8, 2008)

ACPropulsion.com is a world leader for a reason.....AC motor.
Most OEM automotive drive-trains are using their license to be produce an EV.
Regards,
John


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## IamIan (Mar 29, 2009)

sunworksco said:


> ACPropulsion.com is a world leader for a reason.....AC motor.
> Most OEM automotive drive-trains are using their license to be produce an EV.


ACPropulsion produces some fine products , and technologies.

but they are not being chosen because they are the most efficient.

Take a look at the efficiency map of the AC150 ( AC Induction ) drive system ( combination of Motor and controller ) seen on page 6 ( out of 21 ) of the paper from ACPropulsion ( see link bellow ).

http://www.elektromobily.org/w/images/f/fc/Tzero_EVS17_Paper.pdf

That AC150 Induction combination peaks at ~91% efficiency ... which is not bad ... but is still less than the ~97% efficiency of the BLDC combination outlined above.

Combination = BLDC CSIRO Motor + Wavesculptor20 BLDC Controller.

Not just peak efficiencies either ... the entire efficiency curve looks better on the BLDC combination given.

Yes , some specific AC Induction motors are more efficient than some other specific motors in some specific conditions ... but until someone posts a purchasable AC Induction motor with a better efficiency curve ... 

The current winner is still the BLDC combination given.

I do not have any personal attachment to this BLDC combination ... I started this thread hopping someone knew of something more efficient ... I still hope for someone to show something more efficient ... but it hasn't happened yet.


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## yarross (Jan 7, 2009)

Induction motors may be more effcient when operating in deep weakening region. Reason - their excitation current decreases, and for PMACs' counterexcitation current increases when going deeper into weakening.


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## Automcdonough (Sep 1, 2010)

I've been considering the alternator style motor, you drive it like a perm magnet but the rotor has a DC field winding instead of (or in addition to) the magnets. This lets you drop or use lightweight magnets to reduce that light load efficiency hit, but the field control seems great for a variable regen control and potentially much stronger field for DC-like torque. The power for this comes from 2 slip-rings which are much easier to deal with than normal series DC brushes, and could even be replaced with a wireless type setup if you are ok with putting rectifier diodes on the rotor. 

The features/advantages are there but I'm not sure what the efficiency will look like compared to BLDC.


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## yarross (Jan 7, 2009)

Uhm keep in mind, that "alternator style" means claw pole synchronous machine. Maybe you've meant just classic synchronous machine, with electromagnetic excitation?


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## Automcdonough (Sep 1, 2010)

not sure what the difference is to be honest, still on the learning curve here.


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## RoughRider (Aug 14, 2008)

jammydoug said:


> Hi
> How many times more efficient is DC electric motor if operated on outer space and moon compared to same DC electric motor operating on earth?The moon has 6 times less gravity, compared to earth. Space is gravity-less. Gravity is the mother of friction.


is this a serious question?

the losses in a electric motor have nothing to do with friction...

the friction is just in the bearings and it is VERY low...


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## samborambo (Aug 27, 2008)

Automcdonough said:


> I've been considering the alternator style motor, you drive it like a perm magnet but the rotor has a DC field winding instead of (or in addition to) the magnets. This lets you drop or use lightweight magnets to reduce that light load efficiency hit, but the field control seems great for a variable regen control and potentially much stronger field for DC-like torque. The power for this comes from 2 slip-rings which are much easier to deal with than normal series DC brushes, and could even be replaced with a wireless type setup if you are ok with putting rectifier diodes on the rotor.
> 
> The features/advantages are there but I'm not sure what the efficiency will look like compared to BLDC.


If you're considering a wound rotor synchronous machine (as you describe) you might as well go for a sepex (shunt wound DC). A sepex would have similar performance but with a much simpler / cheaper controller.

Then again, what benefit, other than power factor correction, does a wound rotor have over a pure induction machine?

Sam.


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## samborambo (Aug 27, 2008)

IamIan said:


> What induction motor are you thinking of?
> Pared with what controller?
> 
> I am trying to figure out ... personal curiosity ... what is the most efficient combination ... that is actually available to buy is ... so if there is another combination that can do better ... please let me know what it is.
> ...


Let's clear something up. There is NO difference in power electronics between an induction motor controller and a BLDC controller. The main differences in FOC controllers is that a BLDC control algorithm must know the exact mechanical angle of the rotor WRT to the EM field and the induction control algorithm has an extra control step to compensate for slip.

Obviously a lot of R&D has gone into the Wavesculptor. I've seen one vehicle with two of these implemented as hub drive controllers and the performance, on paper at least, is excellent (that particular vehicle didn't push the limits of the controllers nor the motors as it probably would have damaged the chassis). That said, if you throw enough money at a motor controller, you can churn out some pretty high efficiencies. Engineering is the art of compromise - and usually cost vs performance. 98% efficiency may sound perfect but at about $7000 in quantity, is the extra money better off spent on batteries?

Remember that when you're assessing the efficiency of a motor, particularly BLDC motors, you need to consider efficiency vs load vs intended speed range. As I've said, as well as several others, BLDC motors are difficult to overspeed past their BEMF (base) speed. Even with phase advance in overspeed, a BLDC will incur some significant hit in efficiency due to reverse current flow. Induction motors will also have higher losses at higher speed due to eddy currents in the core but, comparing like for like, will not be as severe.

For most electric car conversions, if you decide you must run with BLDC, you'll be keeping your gearbox. To me the whole point of an EV is to do away with redundant ICE technology like the 5 speed shifter and create something much simpler.

Sam.


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## yarross (Jan 7, 2009)

samborambo said:


> Then again, what benefit, other than power factor correction, does a wound rotor have over a pure induction machine?


Better power density and no pullout torque limit?


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## Automcdonough (Sep 1, 2010)

plus using it as a generator for regen, it blows away any other style motor. Like, it could make the brake pads unnecessary if you have a load to dump the juice into that the batts can't take.


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## JRP3 (Mar 7, 2008)

From what I've read the MiniE and Tesla have very strong regen. I can turn the regen up on my AC induction motor such that I'd probably never need brakes, if the batteries could take it.


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## Electric Car-Nut (Jul 5, 2009)

Pardon the intrusion, the bearings maintain the armature/rotor centered overcoming magnetic forces and side loads from pulleys and other loads. they are usually ball type and very low in friction, nearly un-affected by gravity. However Brushes with their SLIDING contact to the commutator are the highest frictional load inside the electric motor and designs minimizing the number and size of the brushes spin more freely.


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## samborambo (Aug 27, 2008)

yarross said:


> Better power density and no pullout torque limit?


Nope. 

Power density appears to be very misunderstood concept on this forum in electrical rotating machines since it relies on the operating speed range. Torque density is more appropriate. If maximum operating speed and voltage were no constraint, power (and therefore power density) in an induction machine will be limited mainly by winding insulation, core losses and bearing load. Mechanically commutated (DC machines) will always be limited by "zorching", ionising the air around the commutator and causing a rather eventful flashover which is a bit of a show-stopper.

Pull out torque for induction machines is usually only apparent when driven from V/Hz controllers or straight online utility frequency. FOC and DTC control schemes will decrease the frequency (for positive torque) in order to avoid pull out.

Sam.


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## samborambo (Aug 27, 2008)

Automcdonough said:


> plus using it as a generator for regen, it blows away any other style motor. Like, it could make the brake pads unnecessary if you have a load to dump the juice into that the batts can't take.


Are you saying that induction motors aren't capable of regen?

Sam.


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## Anaerin (Feb 4, 2009)

Electric Car-Nut said:


> Pardon the intrusion, the bearings maintain the armature/rotor centered overcoming magnetic forces and side loads from pulleys and other loads. they are usually ball type and very low in friction, nearly un-affected by gravity. However Brushes with their SLIDING contact to the commutator are the highest frictional load inside the electric motor and designs minimizing the number and size of the brushes spin more freely.


They're talking about AC induction or Brushless DC motors, neither of which have brushes, nor the friction caused thereby. So for ACIM or BLDC, the only friction is from the bearings.


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## IamIan (Mar 29, 2009)

samborambo said:


> Let's clear something up. There is NO difference in power electronics between an induction motor controller and a BLDC controller.


There is a difference between individual specific controllers... whatever type of motor they are deigned for... not all controllers are equally as efficient.

Sense the question at hand is about finding a more efficient combination of components one can actually buy today ... the theory of operation becomes mute ( for this topic ) compared to the tested performance curves of real devices that one can buy today.



samborambo said:


> 98% efficiency may sound perfect but at about $7000 in quantity, is the extra money better off spent on batteries?


A very good question ... one that can easily span an entire thread / topic of it's own ... and aside from the side note ( already posted previously ) ... is not relevant to this particular thread / topic. 



samborambo said:


> Remember that when you're assessing the efficiency of a motor, particularly BLDC motors, you need to consider efficiency vs load vs intended speed range.


It is already understood and stated that the efficiency will vary ... and is not a set static thing ... and it is agreed that Combination B might have a net operating efficiency that is higher than Combination A under some situations and conditions ... even if combination A has a higher peak efficiency under certain conditions ... if you know of such a combination B ... please post the specific components ... that is the point of this thread.

Thus far the only counter example I've seen ... was given for a AC Induction combination system was the ACPropultions's AC150 ... which while a nice system for other things ... failed to exceed the efficiency of the BLDC combination given ... not just as a peak but , even over a wide operating range.



samborambo said:


> if you decide you must run with BLDC,


Not picking technology arbitrarily ... or based exclusively on theory ... so far the posted combination with the best performance is the BLDC one listed ... if you know of better performing combination of components that can be bought today ... please post it.



samborambo said:


> you'll be keeping your gearbox. To me the whole point of an EV is to do away with redundant ICE technology like the 5 speed shifter and create something much simpler.


Which is another fine topic ... and also could by itself fill an entire thread / topic all by itself.

The only part of that particular point in this thread's context is ... If there is a combination of components you are aware of that would result in a better operating efficiency.

That would be compared to the given combination running without a gearbox ... and with a gear box ... vs some other combination running without a gearbox ... and with a gear box.

- - - - - - - 

We can not possibly hope to cover and go over every topic related to DIY BEVs in one thread / topic ... several of your points are very valid ... I encourage you to further their discussion ... but if we try to discuss everything in one thread ... individual topics can easily get lost in the shuffle.


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## yarross (Jan 7, 2009)

samborambo said:


> Power density appears to be very misunderstood concept on this forum in electrical rotating machines since it relies on the operating speed range. Torque density is more appropriate.


samborambo: I'm talking about 1:1 comparison of induction and synchronous motors, both having the same stator and operational speed. For this case, power density ~ torque density. By freeing the stator from the need of providing excitation to the rotor, one can obtain significantly higher torque.



samborambo said:


> Pull out torque for induction machines is usually only apparent when driven from V/Hz controllers or straight online utility frequency.


By "pullout torque limit" I meant limited span of constant power region, due to falloff of pullout torque. For synchronous machines, this region is somewhat extended.


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## Automcdonough (Sep 1, 2010)

samborambo said:


> Are you saying that induction motors aren't capable of regen?
> 
> Sam.


they can be used as generators but are not great at it, unlike other motors this one acts like it's suddenly half it's size. A BLDC can acheive much closer to it's normal power rating as a generator.

The torque density advantage of DC or synchronous is that you are not limited by the magnetic field strength which can be induced, or what is present in magnets. A powered coil will achieve the strongest field, but since it's powered will likely not achieve the efficiency that a magnet would for most situations.


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## JRP3 (Mar 7, 2008)

Tesla Motors of course looked at both and went with AC induction, citing better average efficiency of induction over BLDC as one of the reasons, cost being one of the others.


> Likewise, when torque levels are low, the B field should be reduced such that eddy and hysteresis losses due to B are also reduced. Ideally, B should be adjusted such that the sum of the eddy, hysteresis, and I² losses is minimized. Unfortunately, there is no easy way of changing B with permanent magnets. In contrast, induction machines have no magnets and B fields are “adjustable,” since B is proportionate to V/f (voltage to frequency). This means that at light loads the inverter can reduce voltage such that magnetic losses are reduced and efficiency is maximized. Thus, the induction machine when operated with a smart inverter has an advantage over a DC brushless machine – magnetic and conduction losses can be traded such that efficiency is optimized. This advantage becomes increasingly important as performance is increased. With DC brushless, as machine size grows, the magnetic losses increase proportionately and part load efficiency drops. With induction, as machine size grows, losses do not necessarily grow. Thus, induction drives may be the favored approach where high-performance is desired; peak efficiency will be a little less than with DC brushless, but average efficiency may actually be better.


http://www.teslamotors.com/blog4/?p=45


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## IamIan (Mar 29, 2009)

JRP3 said:


> Tesla Motors of course looked at both and went with AC induction, citing better average efficiency of induction over BLDC as one of the reasons, cost being one of the others.


minor correction.



> Thus, induction drives may be the favored approach where high-performance is desired; peak efficiency will be a little less than with DC brushless, but average efficiency may actually be better.


In the specific context of their spot car high performance ... 

"*may* be the favored approach" ... and , "average efficiency *may* actually be better" ... is not the same as is better.

As far as I know the only way to get the Tesla combination motor + controller is to buy a Tesla ... pricey as that option is ... it is available today.

I would like them to disclose what they did ( resulting performance wise at least ) for the system after they rebuilt it in house from the AC-150 system we already know is less efficient... I've seen some wh/mile charts ... but those include allot of other variables , separate from the motor and it's controller.

If we had that at least then we would have a better idea of how big a part of the decision was about efficiency vs other things ...

As others have said ... it is often about compromises.

- - - - - - - - - - 

Of course solar cars are all built with efficiency being of highest importance ... and every single one of them that I ever seen win ... As far as I've seen always use a BLDC.


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## JRP3 (Mar 7, 2008)

They are also low powered, low speed, lightweight vehicles in mostly steady state driving, as far as I know, nothing like the real world.


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## IamIan (Mar 29, 2009)

JRP3 said:


> They are also low powered, low speed, lightweight vehicles in mostly steady state driving, as far as I know, nothing like the real world.


Which I will 100% agree with... and is a 100% valid position.

So what specific motor and controller combination do you suspect will have a better operational efficiency? Even if it has a lower peak efficiency... over a wider set of operating conditions.

We can not compare components unless other specific components are listed to compare against.

Not just general ideas and concepts ... but real components that we can buy today ... we can then compare them.

For example:
( Even though it is not as efficient a BLDC as the CSIRO and the WaveSculptor20 )

The BLDC IMA motor and controller from a 2005 Honda Accord Hybrid .... from the pdf posted a little bit ago in a different thread... and the curve from the ACPropultion's Induction AC-150 ... yes they have very different curves ... and each will fit different rolls better than the other ... etc.... etc... yes if the BLDC plays on the AC-150's home turf it is less efficient ... and if the AC-150 plays on the BLDC home turf is it less efficient ... depending on a vehicles operating conditions it 'may' be more efficient one way or the other.

At least with these two specific examples we can make comparisons ... they are real specific components ... that can be purchased today.


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## JRP3 (Mar 7, 2008)

I guess that's the problem with comparing differences of a few percentage points under varying conditions. You'd have to pick your application, pick your power requirements, pick your driving conditions, and then compare different systems within those parameters, which is what Tesla did. You can't just say "X system is the most efficient" if it won't actually work in your specific situation.


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## Automcdonough (Sep 1, 2010)

they are within 1~2% for most of the operational range, I think that unless we nail down a more specific criteria this is splitting hairs between these two motors..


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## IamIan (Mar 29, 2009)

JRP3 said:


> I guess that's the problem with comparing differences of a few percentage points under varying conditions. You'd have to pick your application, pick your power requirements, pick your driving conditions, and then compare different systems within those parameters, which is what Tesla did. You can't just say "X system is the most efficient" if it won't actually work in your specific situation.


I 100% agree the context can very much change just about everything.

however , context is made up of lots and lots of things ... each of which can easily occupy an entire thread all buy itself... and each time one tried to talk about each of them ... it could still be asked to have a complete context ... it is a vicious circle.

My curiosity was about the efficiency of two major components ... the motor and it's controller... as a combination.

So far the CSIRO + Wavesculptor20 ... has given us the best peak efficiency ... no one to date has posted any specific components that can best that combination.

So moving past the peak efficiency toward a question of a more overall net operational window efficiency ... because yes the efficiency is not static.

Instead of trying to define a complete context ... instead perhaps we can remain focused on the components themselves.

Even if the efficiency curve changes ... we can still make comparisons ... is motor A more or less efficient than motor B on a evenly weighted average across the whole efficiency curve? ... is motor A more or less efficient than motor B what % of the operational window? ... 10% ... 80%.... etc... 

So even though the peak efficiency is not currently in question ... and even without a context we should still be able to give a general comparison between two combinations ... even if we understand that any such comparison like anything else can vary depending on a specific context.

For example... we can look at the Honda IMA BLDC motor Efficiency Curve... and the CSIRO Motor efficiency curve ... yes they are different ... but even without a specific context ... yes can see a significant difference in overall motor efficiency.... ( see images attached bellow )

Similarly we can also look at the controller Inverter from Honda for the IMA system ... and we can compare it to the efficiency curve for the Wavesculptor20 efficiency curve... even without a specific context we can still see significant efficiency differences ... not just in peak but in over all operating efficiency.... ( See images attached bellow )

These are both BLDC combination / systems ... but they are not equally efficient ... yes context can change just about everything ... but even outside of context we can still make efficiency comparisons, on the components themselves... and not just peak efficiencies ... but we can compare over the entire overall operating efficiency curve.

Or is a contextless comparison too limited in usefulness?


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## JRP3 (Mar 7, 2008)

Since we need to have parameters to compare I think it's fair look at average efficiency to draw reasonable conclusions. Problem may be in finding that data.


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## aeroscott (Jan 5, 2008)

how does rads/s compare to Hz. it also looks like a small advantage to running more then one motor because of reduced torque


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## IamIan (Mar 29, 2009)

JRP3 said:


> Since we need to have parameters to compare I think it's fair look at average efficiency to draw reasonable conclusions. Problem may be in finding that data.


I am hoping to find a better way to do it ... 

My first pass was a general just look at the chart kind of thing ... looking for the average trend ... 

A more accurate method would probably be to reverse the graphs which give us plotted data points to get back to the data points themselves ... then determine an equation with a high R^2 value to match the data points ... we could then use basic Calculus to directly compare the equations that each represent the data points of each respective motor ... this would not just tell us if A is more efficient on average than B ... but by how much... and once worked out ... we should be able to use the same technique between any two motors ... thus it would be repeatable results ... and not dependent on different people's subjective evaluation of different graphs.

The CSIRO has lots of equations and data already done in the pdfs published about it ... but to compare it to other motors would require us to get equations for those other motors that match their curves as closely as the supplied equations allows us to match the CSIRO curve.

I am not looking forward to the tedious task of pulling an accurate representative equation out of a picture of a graph of plotted data points.


I was toying with the idea of trying to rescale the pictures so they are on the same scale ... and both using RPMs or Rad/s , etc ... but once the graphs are apples to apples ... a area calculation of the efficiencies might be easier .... but sense they aren't simple geometric shapes ... that might just end up back at the calculus side of of things.




aeroscott said:


> how does rads/s compare to Hz. it also looks like a small advantage to running more then one motor because of reduced torque


Sorry they the graphs are not on the same scale.

2Pi Radian / second = 1 hz
2Pi Radians / Minute = 1 RPMs

[ ( ___ Rad/s )* ( 60 Seconds ) / (2*Pi) ] .=. ___ RPMs
1 Rad / s .=. ~9.5493 RPMs


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## samborambo (Aug 27, 2008)

Automcdonough said:


> they can be used as generators but are not great at it, unlike other motors this one acts like it's suddenly half it's size. A BLDC can acheive much closer to it's normal power rating as a generator.
> 
> The torque density advantage of DC or synchronous is that you are not limited by the magnetic field strength which can be induced, or what is present in magnets. A powered coil will achieve the strongest field, but since it's powered will likely not achieve the efficiency that a magnet would for most situations.


Can you cite any reference to induction motors only attaining half their rated performance when in negative torque? I've never come across such a statement before. I can't think of any technical reason why this would be the case.

Just did a quick comparison of peak torque between a netgain warp 9 and a 4 pole aluminium frame 25hp induction motor. 15% more peak torque in the induction motor and 25lbs less weight. These are standard industrial motors - not even optimised for EV use. Plus they're much cheaper than the DC motors I've seen.

Sam.


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## samborambo (Aug 27, 2008)

IamIan said:


> There is a difference between individual specific controllers... whatever type of motor they are deigned for... not all controllers are equally as efficient.


Well if you want to nit-pick. Of course they use different components of cost vs performance. The topologies are identical.



IamIan said:


> Sense the question at hand is about finding a more efficient combination of components one can actually buy today ... the theory of operation becomes mute ( for this topic ) compared to the tested performance curves of real devices that one can buy today.
> 
> 
> 
> ...


Ian, if you start treating the design or specification of components in a system in isolation, you'll be running in the dark. You simply cannot continue a conversation about the most ideal/efficient motor for an EV unless you look at the bigger picture:


Use pattern - mostly the RPM and torque regions it will be working in to attain the required efficiency.
What its driving - selectable gearbox, fixed reduction, etc.
The controller limitations - voltage, current, precision, control algorithm, etc.
Sam.


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## aeroscott (Jan 5, 2008)

IamIan said:


> I am hoping to find a better way to do it ...
> 
> My first pass was a general just look at the chart kind of thing ... looking for the average trend ...
> 
> ...


just saw the post thanks, now to figure it out!just spent 4hrs. posting on the jag/capstone turbine ,burnt!in a good way .added: 9.54 x 100 rads =954 rpm ?


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## samborambo (Aug 27, 2008)

yarross said:


> samborambo: I'm talking about 1:1 comparison of induction and synchronous motors, both having the same stator and operational speed. For this case, power density ~ torque density. By freeing the stator from the need of providing excitation to the rotor, one can obtain significantly higher torque.


I understand you'd rather a 1:1 comparision vs speed - of course it simplifies the discussion. However, the decisions you will make on other components such as gearbox or differential may be strongly affected by the limits imposed on the speed range of the motor. 



yarross said:


> By "pullout torque limit" I meant limited span of constant power region, due to falloff of pullout torque. For synchronous machines, this region is somewhat extended.


I can't see how that's possible. BEMF for a BLDC will keep increasing above base speed. Once the controller reaches its maximum voltage (hence constant power region) the torque will tail off sharply because the allowable volt drop (and therefore current) through the windings is reduced. There are phase advance schemes used to overspeed a BLDC motor but they are limited in range due to voltage limits of the power components and the motor windings.

Induction motors on the other hand, combined with FOC drives can vary the field current (Iq)independent from the drive current (Id). This esentially means the induction motor can function the same as a shunt wound DC motor - reducing the field current as speed increases to keep BEMF within a manageable range.

Sam.


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## aeroscott (Jan 5, 2008)

samborambo said:


> Can you cite any reference to induction motors only attaining half their rated performance when in negative torque? I've never come across such a statement before. I can't think of any technical reason why this would be the case.
> 
> Just did a quick comparison of peak torque between a netgain warp 9 and a 4 pole aluminium frame 25hp induction motor. 15% more peak torque in the induction motor and 25lbs less weight. These are standard industrial motors - not even optimised for EV use. Plus they're much cheaper than the DC motors I've seen.
> 
> Sam.


 is that using the down under "reduced voltage" ,then increasing voltage as hz goes up . nice work . I just felt that would be the case .


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## IamIan (Mar 29, 2009)

aeroscott said:


> just saw the post thanks, now to figure it out!just spent 4hrs. posting on the jag/capstone turbine ,burnt!in a good way .added: 9.54 x 100 rads =954 rpm ?


yes. You got it.

___ radians / second * ~9.54 = ~ ____ RPMs

so 100 radians / second = ~954 RPMs

Of course ~ is because you are rounding off Pi.


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## yarross (Jan 7, 2009)

samborambo said:


> I can't see how that's possible. BEMF for a BLDC will keep increasing above base speed.


Ehm we were talking about induction motor vs wound rotor synchronous one. This makes the difference.


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## IamIan (Mar 29, 2009)

samborambo said:


> Well if you want to nit-pick. Of course they use different components of cost vs performance. The topologies are identical.


It isn't nit picking when from the beginning I have been referring to specific components to still be doing so... it is the very concept this thread was started on.



samborambo said:


> Ian, if you start treating the design or specification of components in a system in isolation, you'll be running in the dark. You simply cannot continue a conversation about the most ideal/efficient motor for an EV unless you look at the bigger picture:


As already stated ... we know the context will have significant influence ... we also know that each tiny piece of the context can each by themselves be an entire thread on their own ... to try and discuss the whole bigger picture all at once , ends up including too many topics and guesses to be usefully confined to one thread / topic.

Most ideal and most efficient are entirely different things... for a wide variety of reasons... this thread is not about most ideal ... which is a very different topic.

The 'bigger picture' is only relevant if the threads topic of 'most efficient motor' were exclusively for a specific predetermined EV context... which is not what I was looking for ... that would be more useful in that one specific context ... but would be just as much less useful in any other EV context.

Put in other terms ... I am looking at it from a 'component level' design of the system not the components themselves ... instead of a 'higher level' design of the system... Yes I understand the 'higher level' design method is far more common to identify the performance requirements first and then determine the components for those requirements second ... but systems can be designed in a variety of ways ... in this specific context I am looking at one metric out of many metrics of motors and controllers ... as I said this specific topic is not trying to cover all the contexts ... but specifically the one metric of efficiency ... and in the metric of efficiency not all aspects of the vehicle but the motor and controller specifically.

Granted this view / method has its restrictions and limitations ... and I understand that.


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## samborambo (Aug 27, 2008)

yarross said:


> Ehm we were talking about induction motor vs wound rotor synchronous one. This makes the difference.


Sorry, when you said synchronous machine, I assume you inferred BLDC. Excuse my rant then.


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## samborambo (Aug 27, 2008)

IamIan said:


> It isn't nit picking when from the beginning I have been referring to specific components to still be doing so... it is the very concept this thread was started on.


So you were hoping to get an answer at the end of this thread that, for instance, the most efficient motor/controller combination is a Solution 1 with a 9" Netgain. Many posters (before I chimed in) identified the flawed logic of the value of efficiency vs battery capacity, peak efficiency vs wide band, etc. That's probably the reason why we're still debating over the type of motor, let alone make and model.



IamIan said:


> As already stated ... we know the context will have significant influence ... we also know that each tiny piece of the context can each by themselves be an entire thread on their own ... to try and discuss the whole bigger picture all at once , ends up including too many topics and guesses to be usefully confined to one thread / topic.
> 
> Most ideal and most efficient are entirely different things... for a wide variety of reasons... this thread is not about most ideal ... which is a very different topic.
> 
> ...


I'm not sure that you do understand the restrictions of your design method. Imagine if an automotive engineer started a clean-slate design of an entire car by first designing the alternator. No consideration made of intended market, performance, budget or any other high level question. A "bottom-up" approach like this appears to me to be utter insanity. I've never seen such a method taught as good engineering practice - for good reason.

Many people have asked me why I'm using an induction motor for my current conversion. My short response has always been, "Because it's powerful, efficient and cheap". The long response is, "Since I have chosen (objectively, due to other design considerations) to use a manual gearbox without the remote gear stick, leading to a fixed reduction, an induction motor provides the widest power band while remaining very efficient at partial loading. Also, the motor cost me US$40 second hand." 

Do you see the difference? My short answer has no context and mostly irrelevant even to another EV DIYer. Do you see now how counter-productive it is to try and prescribe a specific motor/controller without a design context? 

Sam.


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## IamIan (Mar 29, 2009)

samborambo said:


> So you were hoping to get an answer at the end of this thread that, for instance, the most efficient motor/controller combination is a Solution 1 with a 9" Netgain.


Something like that.

Although I was also hoping to see some other examples ( I didn't already know about ) of very efficient motor and controller combinations.

Peak Efficiency could be one category.
Average / Nominal Efficiency could be another.



samborambo said:


> Many posters (before I chimed in) identified the flawed logic of the value of efficiency vs battery capacity, peak efficiency vs wide band, etc.


Not flawed logic ... the limited scope / basis of the intent ... I was one of them in the very first post that acknowledged several other factors that not only influence efficiency ... and that the best efficiency is not necessarily practical or cost effective.... etc.



samborambo said:


> That's probably the reason why we're still debating over the type of motor, let alone make and model.


The debate about what types of motors and types of controllers could potentially do ... I don't see as ever getting anywhere ... it is not real components ... it is what imaginary components might be able to do ... not comparing the real specs and performance of real components you can actually buy today... feel free to continue it if you like ... but it wasn't the direction of my intent ... but if you think that method will get you to the most efficient combination ... good luck.



samborambo said:


> I'm not sure that you do understand the restrictions of your design method.


Fair enough ... but sense I don't have telepathy , I'm not sure what other words I can type that would help you with that.



samborambo said:


> Imagine if an automotive engineer started a clean-slate design of an entire car by first designing the alternator. No consideration made of intended market, performance, budget or any other high level question. A "bottom-up" approach like this appears to me to be utter insanity. I've never seen such a method taught as good engineering practice - for good reason.


I never said the top down / higher level type of design did not have good reasons for it , or any benefits, or was not common ... in fact I already posted the exact opposite ... I am well aware that method is very common and can have some benefits.

Sense I am not intending on designing imaginary components that don't exist, but instead looking specifically at specific real world components that already exist ... a closer variation of your example to my direction would be something like the bellow example:

Refined Example:
Imagine an Automotive engineer starting out the design of a vehicle by looking into what ICE designs / options were the most efficient ... the ICEs that were currently in production somewhere ... ones that were real and not just imaginary or what might be possible, but what was already being achieved ... what available ICE options would maximize his energy conversion from stored chemical energy to mechanical motion.



samborambo said:


> Many people have asked me why I'm using an induction motor for my current conversion. My short response has always been, "Because it's powerful, efficient and cheap". The long response is, "Since I have chosen (objectively, due to other design considerations) to use a manual gearbox without the remote gear stick, leading to a fixed reduction, an induction motor provides the widest power band while remaining very efficient at partial loading. Also, the motor cost me US$40 second hand."
> 
> Do you see the difference? My short answer has no context and mostly irrelevant even to another EV DIYer. Do you see now how counter-productive it is to try and prescribe a specific motor/controller without a design context?


And that very well might have been the best choice motor for your specific context... $40 is pretty sweet.

I understand the benefits of a higher level / or more top down ( usage context first ) approach to the design ... it isn't hard to grasp... Although you don't seem to beleive me... oh well ... shrug.

I do not agree however that it is the only way to design anything... or that any other method is counter-productive... or that there is nothing to be gained from any other method ... etc.


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## Automcdonough (Sep 1, 2010)

samborambo said:


> Can you cite any reference to induction motors only attaining half their rated performance when in negative torque? I've never come across such a statement before. I can't think of any technical reason why this would be the case.


Found this:
http://electojects.com/motors/tesla-induction-motors-4.htm
Guess I was wrong. I was under the impression that although the thermal power rating doesn't change, they just don't put out the same level of power. That might have been a matter of application..


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## IamIan (Mar 29, 2009)

samborambo said:


> So you were hoping to get an answer at the end of this thread that, for instance, the most efficient motor/controller combination is a Solution 1 with a 9" Netgain.


Yes I know you were just using them for instance ... but I figured I'd do a little looking anyway.

Although the Netgain motors are fine for other things ... winning for most efficient does not look like it is going to happen.

There are different Netgain 9" ... but all 3 of them the Impulse , Warp , and Transwarp ... all look less efficient that we have already seen from the CSIRO ... or from the Honda IMA motor ... or from the AC150.

http://www.go-ev.com/images/003_08_04_ImPulse_9_SpreadSheet.jpg
http://www.go-ev.com/images/003_09_02_WarP_9_SpreadSheet.jpg
http://www.go-ev.com/images/003_16_TransWarP_9_SpreadSheet.jpg

I have not yet found a efficiency chart , or spec sheet for the soliton 1 ... to know where it stands in comparison ... do you have any suggestions on where to find it , by all means let me know ... that would be interesting to see.


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## JRP3 (Mar 7, 2008)

You could try PMing Tesseract or Qer.


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## major (Apr 4, 2008)

IamIan said:


> http://www.go-ev.com/images/003_08_04_ImPulse_9_SpreadSheet.jpg
> http://www.go-ev.com/images/003_09_02_WarP_9_SpreadSheet.jpg
> http://www.go-ev.com/images/003_16_TransWarP_9_SpreadSheet.jpg
> 
> I have not yet found a efficiency chart , or spec sheet for the soliton 1 ... to know where it stands in comparison ... do you have any suggestions on where to find it , by all means let me know ... that would be interesting to see.


Hey IamIan,

Those are brushed DC motors. Would anybody think they would be efficiency winners in your contest?

And the Solitron likely does have higher peak efficiency than your favorite rival because it has a single switch in series with the load. So what? They don't advertise it because it really does not matter. Hell, a contactor controller has the highest efficiency.

Regards,

major


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## IamIan (Mar 29, 2009)

major said:


> Hey IamIan,
> 
> Those are brushed DC motors. Would anybody think they would be efficiency winners in your contest?


Hey Major,

Probably not many ... I myself did not expect it ... but to be fair I want to at least look at the published specs first ... I did not want to just rule them out without even looking at the data... and it was at least close to a specific motor and controller suggestion ( even if I don't think it was a serious suggestion ).

They have other traits for other considerations not related the efficiency being looked at here... nothing wrong with that at all.



major said:


> And the Solitron likely does have higher peak efficiency than your favorite rival because it has a single switch in series with the load. So what? They don't advertise it because it really does not matter. Hell, a contactor controller has the highest efficiency.


I have sent a email ... hopefully they do have and will provide an efficiency performance curve ... without that data ... I do not feel justified automatically declaring them or anybody to be more or less efficient than anybody / anything else.

What motor would you combine with the contactor controller in order to yield better combined efficiencies ... peak efficiencies ... or nominal / average efficiencies over the motors operating range? ... after all the 'contest' / 'question' ... is for a combination of a specific motor + a specific controller... what specific contactor / contactor controller were you considering?

As far as it ... 'really doesn't matter' ... as said many many many times ... I/we recognize efficiency is not the only determining factor for real world component selection ... etc ... etc... etc... but for here it is the question being asked.


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## IamIan (Mar 29, 2009)

major said:


> And the Solitron likely does have higher peak efficiency than your favorite rival


Had a nice email exchange with Jeff about Soliton1.

They do not have , publish , or offer any efficiency graphs for the product... that was a bit disappointing.  ... of course their reasoning is sound ... Customers don't asked for it , and it would require several graphs to accurately represent different operating conditions.

However they do claim that in the worst case it is still over 98% efficient.

Which does put it up as the best average overall operating range efficiency ... other controllers might be able to match it at some points , but all that I have seen have significant portions of their operating range that are bellow 98% efficiency.

Which means the only remaining piece needed for the combination is a Soliton1 compatible motor that does not pull the combination down bellow the lead the Soliton1 offers.

I haven't bumped into one yet ... if anyone knows of one, please post.


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## JRP3 (Mar 7, 2008)

I don't think it's possible for a series brushed motor.


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## IamIan (Mar 29, 2009)

JRP3 said:


> I don't think it's possible for a series brushed motor.


That's what I've been seeing ... that even though the Soliton1 controller itself is very efficient ... it is not enough on its own to carry the lower efficiency I have been seeing in compatible motors... to have combined efficiency that is still competitive , with the other contenders ... for this inquiry / thread topic. anyway.


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## DIYguy (Sep 18, 2008)

major said:


> Hey IamIan,
> 
> Those are brushed DC motors. Would anybody think they would be efficiency winners in your contest?
> major


I was at a manufacturing show in Toronto a few weeks ago. One booth had this solar powered electric "car". I came back a few hours later to meet and talk with the guy who built it and drives it. He has several current world records and has even driven it to the arctic circle. Running off midnight sun.... wow. Anyways, his quest was for the most efficient components. What kind of motor does he use?? Brushless DC Wheel Motor.


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## JRP3 (Mar 7, 2008)

DIYguy said:


> What kind of motor does he use?? Brushless DC Wheel Motor.


http://www.diyelectriccar.com/forums/showpost.php?p=205624&postcount=29


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## DIYguy (Sep 18, 2008)

Sorry, I thought the thread was asking about efficiency.....


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## JRP3 (Mar 7, 2008)

It is but we've also been debating real world average efficiency vs peak theoretical. My opinion is if it can't move my EV around in daily driving at the highest average efficiency it's peak efficiency doesn't matter. Others may disagree of course.


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## DIYguy (Sep 18, 2008)

.... and Ian has tried many times to keep the thread focused on what he asked. The attempts to change the intent have been relentless... (way to go Ian... I find this actually very interesting)

as for moving an EV around at high efficiencies.... I dunno man, I would imagine that there are more BLDC motors moving more folks around in their respective EVs than any other motor. Every electric bicycle (and there are millions of them) has one.


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## JRP3 (Mar 7, 2008)

Yup, lightweight, limited speed vehicle  There are probably electric toys using them very efficiently as well, but they can't move my EV at all  I assume we are talking about systems that can drive a full sized EV.....


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## DIYguy (Sep 18, 2008)

ya... like this one....  Just a toy..... 
http://www.greencar.com/articles/wild-pininfarina-fuel-cell-sports-sedan.php


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## JRP3 (Mar 7, 2008)

I'm not saying that BLDC motors can't drive EV's, just don't show me examples of high efficiency motors that can't, i.e. bicycles and solar racers. I don't think even Ian is looking for the most efficient motor that can drive a slot car


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## DIYguy (Sep 18, 2008)

lol, ..it's all good man..


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## IamIan (Mar 29, 2009)

DIYguy said:


> (way to go Ian... I find this actually very interesting)


Thanks.

I like it myself ... but that's also why I started the thread.

So far I think the BLDC combination has shown the highest peak efficiencies in its sweet spot ... but when looking at the overall average operating efficiency for a given combination ... that becomes a different animal... and a bit more difficult to nail down.

I am hopeful others continue to post other motor+controller combinations not yet evaluated ... and I hope to perhaps find a better / less subjective way of evaluating the 'average' operating range efficiency... my first ideas just seem grossly time intensive... so I've been poking around a bit looking for a better way to do it.


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## DIYguy (Sep 18, 2008)

Hey Ian,

Check out this link. They have a 90 - 100kw motor controller with a claimed peak efficiency somewhere over 95% efficiency. They have some kewl products including a special hub motor used by almost all of the Solar racers.... http://www.ngmcorp.com/index.htm

There ... lol try that.


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## JRP3 (Mar 7, 2008)

DIYguy said:


> Hey Ian,
> 
> Check out this link.


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## Jan (Oct 5, 2009)

DIYguy said:


> Hey Ian,
> 
> Check out this link. They have a 90 - 100kw motor controller with a claimed peak efficiency somewhere over 95% efficiency. They have some kewl products including a special hub motor used by almost all of the Solar racers.... http://www.ngmcorp.com/index.htm
> 
> There ... lol try that.


Is that 100kW drive system for sale? And has anyone ever asked them for a price?


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## DIYguy (Sep 18, 2008)

Jan said:


> Is that 100kW drive system for sale? And has anyone ever asked them for a price?


Yes, that's what it is. I just found them today. I have never seen mention of this company before. That could be my oversight.... but more likely they are low volume/high price producers. I sent them an email today. We'll see what comes back. Not too many details on the website.

Cheers,
Gary


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## Jan (Oct 5, 2009)

DIYguy said:


> Yes, that's what it is. I just found them today. I have never seen mention of this company before. That could be my oversight.... but more likely they are low volume/high price producers. I sent them an email today. We'll see what comes back. Not too many details on the website.
> 
> Cheers,
> Gary


Hopefully the response takes a while. The longer I can believe you've hit the jackpot: The perfect drive, for a very very affordable price.


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## IamIan (Mar 29, 2009)

DIYguy said:


> Hey Ian,
> 
> Check out this link. They have a 90 - 100kw motor controller with a claimed peak efficiency somewhere over 95% efficiency. They have some kewl products including a special hub motor used by almost all of the Solar racers.... http://www.ngmcorp.com/index.htm
> 
> There ... lol try that.


I have a pdf for that system... see attached.

They aren't bad ... one of the main competitors of the CSIRO systems in the solar car competitions.

I don't have a spec sheet for the higher power units ... I know they are less efficient than the smaller solar car models ... but I do not have a spec sheet to know how much less... or what their curves look like.


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## Automcdonough (Sep 1, 2010)

about the induction motor generator thing, it just occurred to me that in an application where the output gets rectified it's quite possible that the windings are only loaded near the peak of the waveform.. a simple bridge rectifier would not utilize the motor nearly as well as an active boost PFC.. hence the difference in motor vs generator power levels. I doubt that anyone has bothered to add such a burly PFC just for regen.


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## DIYguy (Sep 18, 2008)

OK so, I sent this to the guys at http://www.ngmcorp.com/index.htm

*Subject: MDF-375 motor and EVC402-266 controller.* 
*Hi there,

I am a DIY electric car hobbyist. I have built my own EV and drive it on the road daily. I am part of a DIY forum with hundreds of others like myself. The components vary from vehicle to vehicle.... but we are always interested in finding good products from reputable companies. There would be significant interest and even potential "group buys" possible if your pricing was competitive ... assuming support, warranty and implied quality are all in place.

Can you give me an idea on pricing, perhaps in single units and 2- 10, 20 - 50 units? We would be interested in more details, more pictures etc.

Please advise.

Regards,
Gary*
*I received this reply......*


_Hello Gary_

_Thank you for your interest in our products and company._

_The MDF-375 system is an older model that was originally designed for an electric bus application. At this point, I am sorry to say, we no longer produce production version of this system. Since this original design of the MDF-375, the technology has been greatly improved. With this in mind, we could build a special order system specific to your application. However, please keep in mind a custom system would mean potentially higher pricing and longer lead times._

_Another potential option would be to use one of the other systems we offer. If you could please provide information about your specific application and requirements we would be better able to match a system to meet your needs._

_Thank you again for your interest and please feel free to contact me anytime if you have any additional questions._
_Regards,_

_Bruce Hsu_


_So.... here is my question... (since I don't have a build going on with any particlur requirements) What do we collectively "want". Please feel free to add to the list..... 

I'm pretty sure these guys will be out of our league WRT $... but what the heck..... GIVE ME YOUR SPECS! 
_


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## Automcdonough (Sep 1, 2010)

personally i would want something that can output 200 ft-lbs into a 2-spd or 300ft-lbs to a single gear reduction.. or a 4 motor combo with each in the 50~100 ft-lb range.


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## DIYguy (Sep 18, 2008)

Automcdonough said:


> personally i would want something that can output 200 ft-lbs into a 2-spd or 300ft-lbs to a single gear reduction.. or a 4 motor combo with each in the 50~100 ft-lb range.


OK! Thank you for that.....


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## JRP3 (Mar 7, 2008)

The MDF 375 was the product that would probably fit the bill for most of our applications. Wonder what it would take for them to build it again, as opposed to a custom build which would likely be more costly.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> The MDF 375 was the product that would probably fit the bill for most of our applications. Wonder what it would take for them to build it again, as opposed to a custom build which would likely be more costly.


ya... 

Kinda get the idea they build ALL custom stuff anyways....


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## IamIan (Mar 29, 2009)

Automcdonough said:


> or a 4 motor combo with each in the 50~100 ft-lb range.


That is in the solar car motors' range.
Pricing bad ... efficiency good.

- - - - - - - - - 

Leads me to wonder ... 

we've seen very high efficiency motors and controller combinations in some of the solar car designs ... I wonder if there is another field out there that would equally attract high efficiency combinations for us to evaluate their specific components?
hmmmm


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