# Companies of PMSM electric motor



## Estaca-Eco-Racing (Sep 13, 2011)

Hello !

I'm new on this forum and I will introduce the project that my team and I have planed for this year. We are building an electric single seat racing car to compet in Formula Student (FS) Challenge : http://www.formulastudent.com/default

We decided to use a AC Permanent Magnet Synchronous Motor for our vehicle, but i encounter some difficulties to find the appropriate one.

The specifications of the motor that we would like is :

- Peak power : *60kW* maximum (FS rules)
- Maximum voltage : *400V* (FS rules)
- *Maximum weight : 25kg*
- Peak torque (used during 5 to 10 seconds max) : approximatly 1*40 to 200 Nm*
- Peak motor speed : minimum of 5000rpm

Car characteristics: 
-	Max car weight : 310kg ( 683lbs)
-	Peak longitudinal acceleration : 0.85g – 1g (g=9.81m/s²)
-Wheel diameter : 2*0.254 meters
-	Max speed : minimum 110 km/h
-	Max torque on rear tires : *750 to 850Nm*

To obtain this torque on the wheels, we will use a reducer.

We are limited for the battery capacity to a maximum of 7250 Wh and a voltage of 400V.


My main problem is that i can't find a such motor, except only one, the Mavilor MA-55 : 

http://www.mavilor.es/pdf_products/ma_series.pdf

This motor has great performances :
- 16.8kg
- max speed : 6000 rpm
- peak torque : 190Nm

If we plan a car top speed of 130km/h (142rad/s with a 0.254m half wheel diameter), we obtain with a reducer of 4.42, a peak torque on rear wheels of 842Nm that matches perfectly !

However, we can't get in contact with this company, so we have to find another electric motor, but we don't find any one that correspond completly to all of our characteristics (especially the weight !)

Here is a list of all other motor that we found, but are twice the weight we limited for the motor :

Baumueller	DSD100
Boschrexroth	MSK101D-0450
Boschrexroth	MSK101E-0200
Boschrexroth	MSK101E-0300
Boschrexroth	MSK101E-0450
SEM	HR190J8-180S
SEM	HJ190K8-180S
EVE	M2-AC15/4-AS/L
Evo electric	AFM-140
Brusa	ASM6.17.12


Thus, I would like to know if you know any company which produce such kind of motors ?

I already have a look in the forum, but i didn't find what me and my team need for our project...

Thank you,

Fabien
ESTACA Eco Racing Team


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## charliehorse55 (Sep 23, 2011)

What rules are you looking at? I am also a member of a team looking to compete in Formula Student electric, the rules for the 2012 competitions are:

600V max
85kW max

Since the peak power is higher I would recommend using AFM-140. While it does weigh more, you can use a very low reduction ratio (1.5:1 say) and get amazing torque off the line. Since you are limited to 85kW battery current, 

85kW / 650 nm = 130 rads/sec / 1.5 gear ratio = 87 rads/sec

87rads/sec / 142rads/sec * 130km/hr = 80km/hr

You should be able to get 1+ g of acceleration until 80km/hr, with a car weight of 400kg or less. While it might be over the weight of the motor, I think in this case you may want to just go for something heavy but powerful. 

Also, much higher top speed than 130 km/hr, although I understand this is not important as the race is mainly lower speed tight corners.


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## muffildy (Oct 11, 2011)

You could go with 2-4 motenergy motors and get the torque/max kw stats desired.
though it looks like scoring is weighted towards endurance; are you sure you want to go all electric? its not very good for endurance.
I dont know anything about what the car needs to do, but you might consider a basic energy calculation.
http://www.wallaceracing.com/Calculate HP For Speed.php
Plug in your estimated numbers...get the required HP to maintain it.
how long will it need to last? example:
Car with coef of drag .2 and a 12 ft frontal area weighing 1000 pounds at 65 mph uses 6.75 HP thats just to maintain a speed with almost perfect road conditions; to accelerate it will of course use lots more.
6.75 hp = 5.03 kw so if you need to maintain this speed for 1 hour that will already use 5.03/7.25 = 69.4% of your power. Which brings us back to how long?
Im going to assume this race is an all day event, this means that you are going to probably need replacement battery packs in order to compete in other events simply because it would take too long to recharge between events, but ive never done this so i dont know how the events are set up and how long they last.


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## charliehorse55 (Sep 23, 2011)

The endurance race lasts about 25 minutes, so they can use about 15kW average power. That's why you need an AC motor for regen. As most of the race is either acceleration or braking, AC motor massively reduces power consumption.


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## Estaca-Eco-Racing (Sep 13, 2011)

charliehorse55 said:


> What rules are you looking at? I am also a member of a team looking to compete in Formula Student electric, the rules for the 2012 competitions are:
> 
> 600V max
> 85kW max
> ...


Hi charliehorse55,

Yes the rules changed since I posted this thread on the forum. In fact our team was looking at rules that was supposed to be applied for 2012 (400V 60kW) but they finaly didn't choose those rules.

Thank you for your help ! Well, I know that the AFM-140 is great for his high torque, but we won't use all its performance because the battery is limited to deliver at maximum 85kW, and this motor can be used at a peak power of 167kW for 60s, but it won't be possible because of the battery limitation power. If i resume, with this motor we will use it for maximum at the nominal values, which mean that we embark aboard the car a high weight motor which won't be use at its best performances. That's why i was trying to find motor with a lower weight than this one, and that can be adapt to the power required for the car ! Please tell me if my reasoning is wrong, maybe i'm doing wrong since the biginning !


Fabien


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## muffildy (Oct 11, 2011)

Trying to run a motor at peak power for long periods of time will overheat it rather quickly. It is better to have a motor run closer to its continuous rating and only use its peak occasionally for short periods.

I dont know how much the motors you are currently looking at cost.
But heres a sample of if you went with the mars 4201
500$ per motor 72v 300a peak 22# per motor
639$ per controller 5.8# per controller
If you went with 4 of them 4556$ it would have a peak power consumption of 86400w. Weight of 111.2#.
Hard to read the graph i found for it, but it looks like it has a continuous torque of around 130 pound/inches or 14.6 nm, i would assume its stall torque is probably around 3 times that, but i cant find any confirmed.
http://kellycontroller.com/mars-4201etek-comparable-pmsmbldc-motor-p-736.html

Alternatively, you could go with 2 me0913 pmac-ds motors
http://www.cloudelectric.com/product_p/mo-me-0913.htm
they have a peak of 30kw each 12kw continuous, it would cost 700$ per motor, and 1400$ per controller; two of them for 4200$ and at around 75% of their peak (44kw) they would be using all of the allowed DC input.
continuous rate around 200 pound inch or 22.5 nm; peak stall torque 90nm.
these weigh 35# each and controller about 10# so 90# total weight if you went with 2 of them.


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## charliehorse55 (Sep 23, 2011)

A little background, this may clear things up:

By Joule's law we know that the power usage of a circuit is equal to the potential difference multiplied by the current, or P = I * V

In an electric motor, the amount of current going through the windings is directly related to the torque output of the motor. In the case of the AFM-140-4, the ratio is 1.81. For every 1 amp of motor current, 1.81 Nm of torque is achieved. To get the peak torque of 650 Nm, 360 amps of current are required. This current value is not affected by motor speed. 

The voltage across a motor is equivalent to the speed at which the shaft is turning. As you increase the speed of rotation, the voltage drop across the motor increases. This is a linear relationship, so the voltage will be twice as large when spinning at 100 rads/sec than 50 rads/sec. 

Thus, the power a motor is using is equal to it's output torque multiplied by the speed of rotation. In order to reach the peak of 167kW the motor must be running at the peak torque of 650 Nm AND be spinning at a very high speed (255 rads/sec!). 

As the FSAE car is limited to 85kW battery current, if we assume 90% combined motor and controller efficiency:

85kW * 0.9 = 76.5 kW of shaft output power

Using peak torque of 650 Nm:

76.5kW / 650 Nm = 120 rads/sec

This means that you can get the peak torque of 650 Nm from the motor whenever the shaft speed is below 120 rads/sec. Using a gear ratio of 1.5:1, that is equivalent to 80 rad/s at the wheels. With your tire size of 0.254m radius:

0.254m * 80 rads/sec = 20.3 m/s

Convert to km/hr

20.3 * 60 * 60 / 1000 = 73.2km/hr

Which means you will be able to get the full 975 Nm of torque at the wheel shaft from 0-73 km/hr. Here is a graph I made to show the output torque vs. vehicle speed, with 0.254m wheels and 1.5:1 gear ratio (when limited to 76.2kW):










EDIT: Added power to the graph for clarity.


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## muffildy (Oct 11, 2011)

Is the power being measured on the wires going to the motor or the wires going to the controller?
If its on the wires going to the controller, then the power you have available is considerably less. 
I read some of the rules, and it looks like cost is an issue that you are going to be judged on - i suspect that motor looks awesome on paper and so will likely look horrible to the bottom line. how much does it cost and can you even obtain one?

*edit*
more specificaly
a kelly controller for example will convert using a sin function
which means that while efficiency is with luck 90%, to get that the power going into the controller is going to be greater than that of going into the motor.
the sin conversion multiplies your amps by around 1.41
so the total amps that the batteries will see for your motor is going to be around 507.6 amps.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> Is the power being measured on the wires going to the motor or the wires going to the controller?
> If its on the wires going to the controller, then the power you have available is considerably less.
> I read some of the rules, and it looks like cost is an issue that you are going to be judged on - i suspect that motor looks awesome on paper and so will likely look horrible to the bottom line. how much does it cost and can you even obtain one?


The power on this graph isn't electrical, it's the mechanical power being produced by the motor shaft. I assumed a motor/controller efficiency of combined 90%, giving a maximum power usage of 76.5kW. The efficiency is probably a bit high, in reality it might be between 85% and 90%. 

Cost is an issue you are judged on - you are required to submit a cost analysis to show how much the car would cost to make if mass-produced at a rate of 1,000 units per year. 

The team usually spends much more than the unit cost for 1,000 cars building their model, so this has to be considered as well. The team I am on has a pretty generous 5 figure budget. 

The motor is available, my friend is using one in his electric conversion. It cost him about $10k. This is well within the range for the team I am on, especially if evo-electric gives us a sponsorship like they seem to be doing to so many racing teams. 

$10k cost to team
$2-6k cost for the 1,000 unit production model

If the team is just starting, it's budget will be much less. The team I am on has a track record of top 10 finishes at the German competition, and winning multiple times at the UK competition.


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## muffildy (Oct 11, 2011)

wow nice, wish the motor was cheaper so i could afford it.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> *edit*
> more specificaly
> a kelly controller for example will convert using a sin function
> which means that while efficiency is with luck 90%, to get that the power going into the controller is going to be greater than that of going into the motor.
> ...


I'm not quite understanding what you are trying to say here....

Power into the controller WILL equal output power (minus losses). If you have 85kW going into the controller (the maximum allowed as per rules), with even just 300V you will only have 284 amps. There are capacitors in the controller that smooth out the battery load into a relatively constant current. 

Even if the current is pulsed, the measuring tool that attaches to the battery cables takes the power load RMS over 1 period of 1 second.


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## muffildy (Oct 11, 2011)

What i mean is that in order for the controller to be 90% efficient it uses a sin conversion.
For example
the motenergy motor inputs 600 amps at 96v into the controller in order to get 420 amps 96 v into the motor.
the electricity is delivered in waves, a RMS reading is the average of the wave.
So to get 360 amps into your motor, the controller needs to recieve 507 amps from the batteries.
I assume capacitors are used to pulse the extra parts of the wave into the motor in order to achieve good efficiency. So while its true the controller is 90% efficient, if you measure the RMS/volts at the cables from the batteries to the controller it will be much higher than that of the cables going to the motor from the controller.
I am not an electrical engineer, i am just going on what ive read so maybe im mistaken.


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## charliehorse55 (Sep 23, 2011)

Estaca-Eco-Racing said:


> Thank you for your help ! Well, I know that the AFM-140 is great for his high torque, but we won't use all its performance because the battery is limited to deliver at maximum 85kW, and this motor can be used at a peak power of 167kW for 60s, but it won't be possible because of the battery limitation power. If i resume, with this motor we will use it for maximum at the nominal values, which mean that we embark aboard the car a high weight motor which won't be use at its best performances. That's why i was trying to find motor with a lower weight than this one, and that can be adapt to the power required for the car ! Please tell me if my reasoning is wrong, maybe i'm doing wrong since the biginning !
> 
> 
> Fabien


Sorry, I think I misinterpreted your message the first time, as being that you couldn't get peak torque due to 85kW rule. Now I understand what you mean...

The advantage to the AFM-140 is that you get more low end torque. With dry warm pavement and slicks on the car, you can get around 1.4-1.5gs of acceleration. With your car's weight of 310kg and wheel radius of 0.254m that means you need 1150 Nm of torque to saturate the wheels gripping capability. With the MA-55, you are limited to a maximum gear ratio of 4.42 to be able to reach 130 km/hr top speed. This limits you to 840 Nm of torque, which is only sufficient for 0.9-1g of acceleration. With the AFM-140, a gear ratio of 2 will give you a top speed of 150+ km/hr, while giving a maximum torque of 1300 Nm, enough to maximize acceleration from 0-65 km/hr.

Here is a graph to show the difference between AFM-140 (blue) and MA-55 (Yellow). Whether the added weight and cost is worth the bonus is up to you.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> What i mean is that in order for the controller to be 90% efficient it uses a sin conversion.
> For example
> the motenergy motor inputs 600 amps at 96v into the controller in order to get 420 amps 96 v into the motor.
> the electricity is delivered in waves, a RMS reading is the average of the wave.
> ...


While this is true for regular AC power, the motor uses 3 phase power. An important property of 3 phase is that the total power travelling through all three phases is constant and does not oscillate like regular single phase AC. Thus, the total power being outputted and inputted into the controller should be relatively constant.

EDIT:

The RMS of the current being transmitted through all three phases is always equal to 1.5 times the peak current on any phase, and the (non RMS) total is always 0. 

So, for example

Phase 1 = 240 Amps
Phase 2 = -60 Amps
Phase 3 = -60 Amps

Then pi/6 later in the phase, 

Phase 1 = 180 Amps
Phase 2 = 0 Amps
Phase 3 = -180 Amps

It will always RMS to 360 motor amps, and thus the motor current (and by extension, battery current) does not ripple. Of course you aren't running the motor in steady state, and there is inductance in the motor etc so you need some smoothing but really there shouldn't be a huge ripple current. 

The difference in current from the motor you linked is because they are talking about the maximum AC current on any single phase being 420A, meaning that the total is 1.5 times = 630 amps (The motor is also running at a lower voltage than the battery pack, so the battery doesn't need to supply quite as many amps). 

In this case, the 360 amps needed by the AFM-140 is the RMS value, or the total current across all three phases. In the link you posted, the current listed is the PEAK current in any single phase. 

The peak current is useful for calculating how thick your wires have to be, while the RMS value shows relative power consumption.


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## muffildy (Oct 11, 2011)

i dont know if that makes the difference you think
Below i linked the motenergy pmsm motor, it is also a 3 phase motor, and it specifically states that it needs 600 amps to get 420 into the motor.

http://www.motenergy.com/me0913.html
Output Power of 12 KW Continuous, 30 KW Peak (at 96 volts)

Designed for long life. No brush maintenance. The motor is 92% efficient at voltages between 24 to 96 VDC. Continuous current of 125 amps AC (180 Amps DC into the motor control). *This is a 3-phase, Y-connected Permanent Magnet Synchronous Motor* with an axial air gap and 3 Hall sensors at 120 degrees electrical timing. It has two stators with a rotor in the center.

1) This is a 4 pole motor (8 magnets). 2) The Phase to Phase winding resistance is 0.013 Ohms. 3) The maximum recommended rotor speed is 5000 RPM. 4) Voltages from 0 to 96 VDC input to the control. 5) Torque constant of 0.15 Nm per Amp 6) The Inductance Phase to Phase is 0.10 Milli-Henry with a 28 turns per phase. 7) Armature Inertia is 45 Kg Cm Squared. 8) *Continuous current of 125 Amps AC (180 Amps DC into the motor control)*. 9) *Peak current of 420 Amps AC for 1 minute (600 Amps DC into the motor control)*. 10) Weight of 35 pounds. 11) Peak Stall Torque if 90 Nm. 12) This is an Open Frame, Fan Cooled motor.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> i dont know if that makes the difference you think
> Below i linked the motenergy pmsm motor, it is also a 3 phase motor, and it specifically states that it needs 600 amps to get 420 into the motor.
> 
> http://www.motenergy.com/me0913.html
> ...


I replied to this post, but because of a bug in the forum it got injected before your post??? weird. Anyways, I explained the difference between peak current and RMS in my post (1 above yours).


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## muffildy (Oct 11, 2011)

ah that explains it, so very confusing.
Well, i read up on the pdf file for the AFM-140 a bit
http://www.evo-electric.com/inc/files/AFM-140-Spec-Sheet-V1.1.pdf
It looks very nice, i wish it was cheaper.
But i did notice a chart at the bottom you might not have.
It looks like your rpm is going to be severely restricted using this motor because of your 400v limit
the chart seems to indicate only for 320v 450v 600v and 750v
Since you can only go 400v max that means your stuck at the 320v point
and at the 320v point the motors top rpm is 2850 which is considerably lower than the 5000 rpm you originally desired.
to get 5000 rpm it looks like you need to go to 600v
*edit*
oh and the nm/a ratio is only 1.36 for that volt and that winding.
1.81 nm/a needs 750v


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## major (Apr 4, 2008)

charliehorse55 said:


> The total current being transmitted through all three phases is always equal to 1.5 times the peak current on any phase.
> 
> So, for example
> 
> ...


The sum of the instantaneous currents in a balanced 3 phase system equals zero.


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## charliehorse55 (Sep 23, 2011)

major said:


> The sum of the instantaneous currents in a balanced 3 phase system equals zero.


Sorry, I meant RMS. I'll edit my post to include that.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> But i did notice a chart at the bottom you might not have.
> It looks like your rpm is going to be severely restricted using this motor because of your 400v limit
> the chart seems to indicate only for 320v 450v 600v and 750v
> Since you can only go 400v max that means your stuck at the 320v point
> ...


No need for 5000 RPM, because the 2:1 gear ratio you only need about 1500 motor RPM to hit 150 km/hr. 

Also, the voltage/rpm curve is linear, they have just made a table as a rough guideline. With 400V pack voltage you actually get a maximum RPM of about 2600 RPM.


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## muffildy (Oct 11, 2011)

thats going to be hell on your low speed efficiency, hopefully none of the events have very much complete stop/start like city driving or your batteries will drain too fast.
hp = (torque * RPM) / 5250 

So if your rpm is low, but torque is high your resulting HP is going to be low
Which means you could be putting in your 85kw of power, but getting out only 10kw of power, low rpm = extremely inefficient.
thats part of why some smart people made electric motors use a transmission as well so that they can run higher rpm which is more efficient.
but it sounds like you want to go with a simple ratio connection.

*edit*
on rereading that, it sounds a lot ruder than it did in my head yesterday
sorry i didnt mean to imply anything, i know your most likely smarter than i am.


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## Dennis (Feb 25, 2008)

muffildy said:


> thats going to be hell on your low speed efficiency, hopefully none of the events have very much complete stop/start like city driving or your batteries will drain too fast.
> hp = (torque * RPM) / 5250
> 
> *So if your rpm is low, but torque is high your resulting HP is going to be low*
> ...



Your statement is not quite correct about high torque at low RPM is less horsepower. If the speed of the motor is low because of load then the horsepower will increase, even though the motor is slowing down. The rate of change of the torque is what you did not consider vs. rate of change of the RPMs. If you lose 10% of your full load speed from a load increase, but gain 60% in torque then horsepower will increase.

DC brushed motors for example produce maximum shaft horsepower at 50% efficiency if loaded down to this point which is halfway RPM point between the 0 RPM point which is max torque to no load RPM point (not for series wound motors of course!!). Although no one in their right mind would try to gain peak horsepower in this manner due to the bad efficiency and major stress on the motor's windings from the I^2R losses of the high current. So to get more power, drag racers will increase the voltage well beyond the motor's nominal rating so that they get horsepower from the speed increase rather than torque which results in a cooler running motor since the current will not be high and the motor is spinning faster so the fan can cool it better.


Also keep in mind that the torque curves and power curves you get from Dyno runs are the characteristic of the controller's current limiting and the fact that you are accelerating a mass which does not require torque to go up as it spins faster if the torque is being maintained as the RPMs are increasing which a motor controller with active current limit does to the torque of a motor if a mass is being accelerated from rest.


For instance if I took a brushed DC motor and attached its shaft to a flywheel and got a motor speed controller with active current limit ability and had the throttle input at 100% from when the motor is not spinning up till the motor is at full speed then what will happen is that the current limiting circuit will limit the current since at the start the motor is not producing any back EMF so the controller's current limiter is limiting the current and therefore the torque will be limited. This will continue until the back EMF is sufficiently high enough that the current sensed by the controller is no longer higher than the limit, and thus the controller will no longer be in current limit mode and the motor's torque will be falling off rapidly from the back EMF. So the torque curve will be a horizontal line from zero RPM till at some point where the back EMF causes the the current to become less which will show the torque curve decreasing.


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## major (Apr 4, 2008)

muffildy said:


> Below i linked the motenergy pmsm motor, it is also a 3 phase motor, and it specifically states that it needs 600 amps to get 420 into the motor.
> 
> http://www.motenergy.com/me0913.html
> Output Power of 12 KW Continuous, 30 KW Peak (at 96 volts)
> ...


Hi muffi,

I've seen this motor spec before and it bothered me. Look at efficiency at the continuous and peak points with the DC values and stated output kW values. 

12000W output / (96V * 180A) = 69.4%.

30000W output / (96V * 600A) = 52.1%.

I doubt these are true figures and the web site author hasn't a clue as to what he types into it. I think this illustrates the pitfalls of taking an advertisement and drawing generalized conclusions from information contained there within.

Regards,

major


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## muffildy (Oct 11, 2011)

which controllers use active current limiting? i thought most of them use a static current and vary the amps. If you can limit the current like that it would dramatically increase efficiency like you were saying.

its confusing when manufacturers give out data like that.
For example, if 96v 125 amps = 12kw then it would be 100% efficient, which is impossible. 
96v 420 amp = 40.3kw which would make it 75% efficient, which is more believable.

I found a excel file for a different kind of motor - the ac-12 induction motor, and it starts out at like 8% efficiency 50 rpm 117nm torque so the longer its in low rpm high torque mode the faster the battery would drain.


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## muffildy (Oct 11, 2011)

something i just thought of...
"We are limited for the battery capacity to a maximum of 7250 Wh and a voltage of 400V."

wouldnt this mean that you are limited to 7250/400 = 18.125ah?
I dont think there are any cells that work out to exactly that ah.
you would need a battery capable of delivering 20C continuous to power the motor though if you did have cells for it.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> something i just thought of...
> "We are limited for the battery capacity to a maximum of 7250 Wh and a voltage of 400V."
> 
> wouldnt this mean that you are limited to 7250/400 = 18.125ah?
> ...


You are limited to 600V as the peak voltage between any two terminals at any time. Thus, you want a pack that has a peak voltage after charging no higher than 550V or so. Don't want to get disqualified. 

Batteries of those specifications do exist, for example Dow Kokam has 50C batteries that also get 140 Wh/kg! 

http://www.dowkokam.com/cell-specifications.php

Pricey, but you only need a 7.5 kWh pack.


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## muffildy (Oct 11, 2011)

wow those cells are amazing


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> wow those cells are amazing


There's a reason they cost $800/kWh... 

They also have 5C cells rated for 200 Wh/kg. About the same cost. 

Thunderskys for comparison are about $380/kWh.


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## muffildy (Oct 11, 2011)

well, considering 10k just for the motor isnt unreasonable i would expect that those ridiculously expensive batteries will be within budget as well.

its too bad these companies want so much for their products - granted they are better than the other options, but theyre priced far far too high for what they are.


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## muffildy (Oct 11, 2011)

i found a motor even more powerful (and more expensive) for your consideration:
http://currentevtech.com/Drive-Syst...ers/120KW-BLDC-Motor-and-Controller-p168.html


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> i found a motor even more powerful (and more expensive) for your consideration:
> http://currentevtech.com/Drive-Syst...ers/120KW-BLDC-Motor-and-Controller-p168.html


-Less power
-Less torque

175kg + 45kg controller

What was better about this?


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## muffildy (Oct 11, 2011)

AFM-140:
220 nm continuous
600 nm peak
400v 360 amp; you stated 2600rpm is your expected max

This motor is:
191 nm continuous
635 nm peak
it can run at 400v 360 amp as well, but its rpm is likely going to be closer to 4500 or so instead. though its hard to say without a V/rpm listing.

So you could use a different gear ratio to connect to the wheels and end up with higher nm at the wheel.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> AFM-140:
> 220 nm continuous
> 600 nm peak
> 400v 360 amp; you stated 2600rpm is your expected max
> ...


175kg vs 40kg....

Also, there is a limit to how much torque can be put through the wheels. 1.6g (what the AFM-140 provides) is already past the amount of torque (assuming no aerodynamic downforce) and so anything further would not aid the car's acceleration. You'd be carrying around 135kg for nothing.


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## muffildy (Oct 11, 2011)

well i suppose another option is the heinzmann SL-EC 180 type 22B
6000 rpm
22.3 nm nominal
89 nm peak
150v 117.5 to 522 amps
using a reducer at 4.4 or so and two of the motors you would get 783nm
weighing 22.3kg each so 44.6kg plus controllers
i didnt have any luck contacting the company for it though.

Though i wonder about the usable power.
you said earlier 85kw is the max allowed?
85000/400 = 212.5 amps max for the AFM-140
85000/300 = 283 amps max for the heinzman dual motors.
So it looks like either motor would only have peak amps allowed to it when its running at lower volts.


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## charliehorse55 (Sep 23, 2011)

muffildy said:


> Though i wonder about the usable power.
> you said earlier 85kw is the max allowed?
> 85000/400 = 212.5 amps max for the AFM-140
> 85000/300 = 283 amps max for the heinzman dual motors.
> So it looks like either motor would only have peak amps allowed to it when its running at lower volts.


Exactly. The controller converts the pack voltage and current into a different current and voltage value for the motor. As long as the pack voltage is higher than the motor voltage, the motor can continue to turn. The motor voltage is directly related to the shaft speed of the motor. 

Thus, if you look at the graph, the AFM-140 can only get peak torque (360A of current) until the motor voltage hits about 230 volts. At this point the controller will be converting 400V and 210 amps into 360A and 230V (Some energy is lost in conversion)


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## Arlo (Dec 27, 2009)

Did I read correctly you want to use a permanent magnet 3 phase motor? SO a BLDC? The problem is fining a controller to run it! Im working on this as well with a motor that's ~15kw continuous 50kw peak (for 10 seconds) and there is no controller in the world to run it so I am designing one (with a lot of help)


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## muffildy (Oct 11, 2011)

i wonder how the afm-140 performs with repeated use of launch torque
its rated for just 18 seconds at the 600nm rating, it looks as though your graph is suggesting you use it in a continuous fashion...so after 18 seconds what happens? overheat? meltdown?
Lets say you use the 18 seconds of launch torque, and then switch to the 400 nm of peak torque? will it be too hot from launch torque or can it go an additional 42 seconds in peak?

Im betting it wont handle it very well - does your friend who owns one want to test it out?

Question then is how long are the other motors rated for running their peak?


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## muffildy (Oct 11, 2011)

efficiency thoughts:
Nm = (kW x 9549)/RPM

Assuming it takes 5kw to maintain 65 mph
Nm = (5*9549)/2600 = 18.36 nm
Now, the efficiency graphic for the AFM-140 shows that it is least efficient at low torque at almost any rpm. Im guessing it will only be between 75 and 85% efficient at maintaining 65 mph; difficult to tell just which line it will land on in the graph since they overlap.


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## Dennis (Feb 25, 2008)

muffildy said:


> which controllers use active current limiting? i thought most of them use a static current and vary the amps. If you can limit the current like that it would dramatically increase efficiency like you were saying.


What I mean by active current limit is that the sense element inside the controller that is used to measure the current has its data compared against the setting that the user set the current limit to. If the compared current from the sensor is higher than what the setting is, then the controller takes corrective action by means of shutting down the power switching devices during that time the current is above the setting. In fact the controller is doing this on/off switching very rapidly. Btw, Amperes is the units of measure of current much like meters is the units of measure of distance. So the statement that current is "static" does not make any sense.


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## muffildy (Oct 11, 2011)

i meant volts
*edit*
more specifically, most controllers use pulse width modulation to simulate a sin wave of electricity. So instead of just sending out 24 volts, it sends out 96v pulsed say 4 times.
So the motor thinks its receiving 24 volts, but its actually recieving 96 over 4 times the length of time. If instead a controller could actually send out 24 volts it would be more efficient. but i dont know of any that can actively vary their voltage.

Oh, and i just figured something out with regards to the launch torque that motor has...
If you solve that equation nm = kw*9549/rpm for rpm using the known inputs you get:
85kw*9549/1200nm = 676 rpm. So it would be defying the theoretical limits to exceed that 676 rpm. If you solve for 800 nm its 1014 rpm, so i would assume that as soon as rpm = 1014 the advantage of the AFM-140 is gone.


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