# Not quit sure what I have hear, need some input



## Guest (Jul 9, 2010)

Get the inverter if you can. It is the controller for your ac drive motor. The duty cycle is showing the duty for 60 minutes. Looks pretty stout. Others will pipe in on the AC stuff. If you can get a decent controller for your motor then you may have a decent drive motor that will also give you regen. Maybe a curtis AC controller will work. They are lower voltages but should give decent performance anyway. 

Pete


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## Guest (Jul 9, 2010)

72 volts minimum for any EV converted automobile AC or DC. I'd say go with the 98 volt or what ever that curtis spec is for their AC controller and go with some Lithium. It will allow freeway speeds but will give you good performance below hwy speeds. Go with more than what you might think you would need. You will be glad you did. What about those times when you might want to go faster, you will have it if you go higher voltages. What about other peoples perception of the electric car conversion if all you do is make a street legal golf cart? Ouch. Give your conversion some balls. You will be happy you did. 

Pete


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## Guest (Jul 9, 2010)

What are you planning on converting and what is your budget and your expectations? 

Pete


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## just_a_zoo (Jun 22, 2010)

I'm converting a Mazda 323, I'm epecting 75-100km per charge, and would like a vehicle capable of highway speeds... just not at the expense of cooking a motor. I guess I'll shoot for the moon, and if it doesn't work out, I'll call it a learning experience  I will be getting the controller, inverter, and whatever other guts I want from the forklift on Thursday. Then I'll probably have a better idea of what I'm up against. I'm hoping to keep the total cost under $7000.... The car is sitting in my drive unable to pass emissions, so theres no cost there (we already got 10 good years out of her) and the forklift parts were $250 for anything I want off it. I have access to a machine shop, so no cost there, just time. The biggest items will be the contrller, batteries and charger.


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## major (Apr 4, 2008)

just_a_zoo said:


> I got this motor for a song, and the original controller is available to me. It came out of a fork lift, and I ASSUMED it was a DC motor and had planned my build around that (bad me, I should know better). Anyway, it's a 36V 3~ 7.5Kw going into a mazda 323. The purpose of the vehicle is for dropping the kids of at school and going to work, no highways involved. My problem is I'm not sure how to go about raising the voltage for an AC motor. Can I just get a high voltage controller? Would the 36v be enough for city driving? Should I make an attempt with this? or should I ditch this and go with my original plan of using a DC motor. I would like to use what I have if possible. Here's the specs...
> 
> Brand: API Elmo
> Motor: 3~ 87hz
> ...


Hi just,

Looks like an AC motor (induction motor probably). 34 volts is likely the phase voltage (AC), so the DC voltage to the inverter (controller) would have been 48 (battery). But still low for an EV car. The 174 amp rating is for one hour, so you may be able to run it to 4 or 500A for short periods. If you double the voltage (96V battery) and run it to 175 Hz (5000 RPM), then you could have something which could do well in a car, I think.

But an AC drive may not be for the first time EV converter. If you don't want to try AC, I bet there are others on this forum who would like to give it a shot with that motor. 

Regards,

major


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## just_a_zoo (Jun 22, 2010)

major said:


> Hi just,
> 
> . 34 volts is likely the phase voltage (AC), so the DC voltage to the inverter (controller) would have been 48 (battery).


Your right, it is a 48v battery.



major said:


> But an AC drive may not be for the first time EV converter. If you don't want to try AC, I bet there are others on this forum who would like to give it a shot with that motor.
> 
> Regards,
> 
> major


I've been doing the research and I think I'm up for the challenge... But I may be able to get more of these.


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## toyolla2 (Jun 21, 2010)

Motor: 3~ 87hz 
7.5Kw 2500 rpm
34 volts 174A

Let's see....

Conventional 60Hz motors have speeds like 1200, 1800, 3600 rpm
This would be for 3,2,1 pole pair machines resp

Most motors are rated 1800rpm and contain 2 pole pairs per phase
They are colloquially referred to as 4-pole motors
I'm guessing that's what you have.

The unusual speed figure of 2500rpm is not so unusual since the rpm
can be anything you like providing you drive the motor with the appropriate frequency.

Let us take that 4 pole motor described earlier and drive it with 87Hz current. Then (87Hz/60Hz) times 1800rpm = 2610 rpm 

That answer is sufficiently close to 2500 rpm to tell us that this is indeed a 4 pole machine. Notice the difference 2610 - 2500 = 110rpm is the slip.
This snippet of info can be used to tell the AC controller how your motor behaves on full load. That knowledge will allow some controllers to perform better.

As was mentioned earlier this motor can be run from much higher voltages like 96v and even 144v if you so wish. Yielding 68Vac and 102Vac resp.

However you will need to expect proportional increases of speed to 5000 and 7500rpm. The continuous maximum torque will be limited to whatever you had on the 48V battery at 174Amps.

As with any AC motor you may exceed the continuous current rating by 300% to 400% for up to 30 second intervals. Even a safer 300% would be 500 amps and there are EV controllers for this. 

We started out with this motor having a continuous power rating of 7.5,15,22.5kw resp depending on the battery voltage you chose.

Of course if your controller can supply 500 amps, you can further multiply those figures by three then the 7500 rpm motor can peak out at 67.5Kw or 90Hp !

A motor like this deserves an encoder on its non driving shaft and a vector drive. A good external fan to keep things cool. 

The downside is an expensive controller - not sure the fork lift will cut it.
The vehicle will also need 10:1 to 8 :1 overal ratio.


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## just_a_zoo (Jun 22, 2010)

Thanks Toyolla, I had most of that info circling around in my head, but couldn't quite string it together. You have lit a bright light at the end of the tunnel. You spoke of an 'encoder' on the non drive end... There is something on the non drive end, some sort of sensor with 4 wires going to a harness. I'm waiting for the original controller so I can see exactly where that harness goes and what it's for. I thought it might be a hol fx sensor, but I'm not sure. Thanks for your info. 90 hp.... wow


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## samborambo (Aug 27, 2008)

I agree with major and toyolla2. You can extrapolate the motor performance out for higher voltage/speed. However, there are a couple of drawbacks:

The iron losses (heating) will increase proportional to the square of the frequency. So doubling the speed will quadruple the iron losses. Iron losses are standing losses, regardless of current/torque.
The skin effect of a higher frequency on the copper windings. Transient current tends to travel on the outside of the copper wire, effectively reducing the cross sectional area of conductor available and therefore increasing resistance of the wire. There's not much you can do about this unless you're planning on rewinding the motor, in which case you might choose many smaller wires run in a parallel bundle to increase the surface area.
At 87.5Hz, the AC resistance is 90% more than the warm DC resistance. This will increase linearly (180% for 175Hz, etc.). The actual heating effect will be even worse since it's P = I^2 * R.

At 175Hz/5000RPM, your iron losses will increase by 300%.

At 263Hz/7500RPM, your iron losses will increase by 800%.

Two mitigating factors that should help:


An axial fan on the N end will help reduce those iron losses since the air flow will increase with speed.
Not as much torque / current is needed at high speed, reducing the heating on those windings.
Hope this helps.

Sam.


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## major (Apr 4, 2008)

Hi Sam,

Some valid points. A few comments from me 



samborambo said:


> I agree with major and toyolla2. You can extrapolate the motor performance out for higher voltage/speed. However, there are a couple of drawbacks:
> 1.) The iron losses (heating) will increase proportional to the square of the frequency. So doubling the speed will quadruple the iron losses. Iron losses are standing losses, regardless of current/torque.


I think it is actually less than a squared function WRT frequency, something like "to the 1.6 power". And this only affects the stator iron. But you are correct, hysteresis and eddy current losses increase with frequency. 



> 2.) The skin effect of a higher frequency on the copper windings. Transient current tends to travel on the outside of the copper wire, effectively reducing the cross sectional area of conductor available and therefore increasing resistance of the wire. There's not much you can do about this unless you're planning on rewinding the motor, in which case you might choose many smaller wires run in a parallel bundle to increase the surface area.


I am not sure about this particular motor, but it is common to use multiple strands to wind ACIM stators in the first place just to facilitate assembly. So this may be not be a big problem.



> Two mitigating factors that should help:
> 
> 1.) An axial fan on the N end will help reduce those iron losses since the air flow will increase with speed.


The fan does not affect the iron losses. It can assist in the removal of the resulting heat. But if I were to double or triple the speed of this motor, I would consider removing the shaft mounted fan and using another cooling method. That fan may not be suitable for the higher speeds.

I do agree with your basic premise. Run a motor at higher speed or load than which it was designed for, expect higher losses. Meaning lower efficiency. But in a vehicle where size matters, it can be worth it  We're talking about budget projects where they guy can't rewind it or change to high grade thinner laminations. Is it much different from how low voltage forklift DC motors are applied to EVs?

Hey just_,

I might be interested in one of these motors. Drop me a PM.

Regards,

major


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## samborambo (Aug 27, 2008)

major said:


> Hi Sam,
> 
> Some valid points. A few comments from me
> 
> ...


Definitely a square function. I'm even surer than I was about the panetary gear torque problem 



major said:


> I am not sure about this particular motor, but it is common to use multiple strands to wind ACIM stators in the first place just to facilitate assembly. So this may be not be a big problem.


I should have elaborated a bit further. I work on a rule of 10% increase for 50Hz rise in frequency based on a single smooth circular conductor. That's the rule of thumb for overhead line design.

Regardless of how many strands, if you can determine the warm DC resistance and the AC resistance at normal operating speed, you can extrapole the resistance increase with speed.



major said:


> The fan does not affect the iron losses. It can assist in the removal of the resulting heat. But if I were to double or triple the speed of this motor, I would consider removing the shaft mounted fan and using another cooling method. That fan may not be suitable for the higher speeds.


Brainfart on fan reducing losses. It should read fan reducing iron heating/temperature.



major said:


> I do agree with your basic premise. Run a motor at higher speed or load than which it was designed for, expect higher losses. Meaning lower efficiency. But in a vehicle where size matters, it can be worth it  We're talking about budget projects where they guy can't rewind it or change to high grade thinner laminations. Is it much different from how low voltage forklift DC motors are applied to EVs?
> 
> Hey just_,
> 
> ...


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## just_a_zoo (Jun 22, 2010)

So this is what I'm understanding in a nutshell. I can safely increase the voltage to the motor as well as increasing the frequency to pull my little car. The overall continuous torque doesn't change. In turn for horsepower I sacrifice efficiency which, in turn, results in heat. Limiting the current at higher speeds will help reduce the heat, and an axial fan or some sort of blower will be needed to help dissipate the heat that is generated. So with all this in mind, and I take the necessay cooling steps... 96volts should be within my grasp?!


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## toyolla2 (Jun 21, 2010)

Sam
I sure would like to see that equation for skin effect you're using. AC resistance 90% up (that's almost double) from the DC resistance at 87.5Hz.

Then however does a loudspeaker voice coil ever achieve performance at higher frequencies without rolloff if skin effect were to be that severe ? 

Regarding iron loss. Of the two types : 
Hysteresis is proportional to frequency - but the coefficient is tiny therefore the effect is not considerable. So you didn't mention it. For only a threefold increase I'll concur.

Eddy current loss proportional to the square of the frequency would be serious. But now that you've pointed out to us the severity of skin effect to which I assume the flow of eddy currents are also susceptible, should I propose we can ignore that too ? Please excuse my mild humor.

Now about that encoder. If it is a hall effect sensor and we are dealing with a brushless motor then I wouldn't exceed 250 Amps phase current. You could demag the rotor otherwise. Previously I have been assuming an AC induction motor. I suggest you find out which type you have. Put a digital voltmeter across two of the phase wires and see if there's any Back-EMF when you rotate the motor by hand, which would mean magnets on the rotor.

I see that major and sam have posted again since I began. I was interrupted by the sale of my 400Amp ASG I might add. So some of the points have now been thrashed out. 

One thing Zoo mentioned is loss of efficiency - as if it were a bad thing. Having increased losses at higher powers is OK.

If you are putting out three times the power at 7500rpm and losses had remained the same then the motor effcy would have *improved* by three times. I.E. a previous 90% system would now be 97% efficient !!
If losses increase with power then effcy *remains the same*, but you have a motor of one third the mass. Anyway fan cooling by a couple of small units directed into the motor should fix that.

The real problem here is getting the 7500rpm to the 1000 rpm axle speed at say 60 mph. These are the interesting mechanical issues that need addressing rather than the rube workarounds like my generation did in the past. 

It's nice to get some AC parts for almost free - try getting an easily available 460Vac induction motor rewound to 25Vac for $250 - although for the true advantage you still need to make that investment in mechanical engineering. A successful powertrain doesn't just rest on one part. The battery, the controller and geartrain also have to be up to snuff else you may as well limit to 45mph and avoid travelling on major hiways even for very short trips. This vehicle needs to be easy to drive. An electric motor feeding into a 5-spd gearbox is not the answer. Plus some econobox gearboxes are not happy with inputs above 7000rpm I can tell you.
The large speed range offered by an AC motor drive allows you opportunity to dispense with that.
With those words, Zoo, I wish you luck with your project.


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## just_a_zoo (Jun 22, 2010)

OK, so today I went and picked up the inverter. It is made by Atlas Copco and is an AC SuperDrive.... I also took apart the motor to see what that sensor is, and had a WTF moment. The 4 wires go strait into the bearing. With that said, I did a little bit of a google investigation and this is what I found.

"By incorporating features such as speed feedback using the SKF sensorised bearing, AC drive systems can match the cost of traditional DC drives while giving performance benefits. Atlas Copco Controls' AC drive system for forklift trucks allows the use of a regular induction motor, albeit a special version. The control system is used for both the main traction motor and the pump motor that operates the hydraulic functions.
Atlas Copco Controls developed the new system, AC SuperDrive, together with the Swedish manufacturer of forklift trucks, BT Industries AB, and electric motor producer, ELMO Industrier AB. The control system gives optimised torque throughout the speed range, while the truck has lower maintenance time and cost, fully regenerative braking - resulting in minimum brake wear - plus a number of other benefits. The first model to use this system, the new reach truck BT Reflex AC, was launched in October 1997. The difference in performance has been noticeable with improved capacity (pallets per hour) and better lifetime cost efficiency of the truck."

http://evolution.skf.com/zino.aspx?articleID=52&lan=en-gb


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## Billduck (Apr 18, 2009)

One of the AC Superdrives is available locally, and the motor is 12.7kWatt, but the battery pack voltage is 36. (Yea, it draws a lot of amps at peak acceleration) I had always thought that the minimum EV voltage was 72. But given that the motor is the same watts as the motor in my Force, I was thinking that the 72 volt rule is not correct. Thoughts?
Thanks, Bill S


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## Guest (Sep 24, 2010)

I think you will be running killer amps with 32 volts.


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## Billduck (Apr 18, 2009)

The specifications say the drive is rated for 300 amps for an hour. The following is a link to the product data sheet. I have been contact with the Kollmorgen rep, and he may be able to get some electrical schematics. Even for an older drive. 
http://www.kollmorgen.com/website/com/eng/download/document/ACS.pdf
Bill S


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## just_a_zoo (Jun 22, 2010)

Hey Bill. Mine looks quite a bit different, it's a 2nd generation, but as I understand it, the difference between them is that yours is a more compact version, but functions the same. I also heard, but can't verify this, that the superdrives rated 24v, 36v, and 48v are all actually the same drive and will operate at any of those voltages. If you come across any more info on these drives, let me know. I'm desperatly in need of a wiring diagram for my generation 2 drive. Thanks, Mike


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## peggus (Feb 18, 2008)

It's not quite that bad. 

Iron losses consists mainly of hysteresis losses and eddy current losses. Hysteresis losses are proportional to frequency and eddy current losses are proportional to f^2.

Skin effect is not an issue at these frequencies, since the skin depth at 100Hz is 8mm, 4mm at 200hz, etc. I doubt this motor is wound with such thick wire.... Keep in mind that it was designed to be driven by a switching motor controller operating at 10s of kHz so a few hundred hz is not going to make any difference.








samborambo said:


> I agree with major and toyolla2. You can extrapolate the motor performance out for higher voltage/speed. However, there are a couple of drawbacks:
> 
> The iron losses (heating) will increase proportional to the square of the frequency. So doubling the speed will quadruple the iron losses. Iron losses are standing losses, regardless of current/torque.
> The skin effect of a higher frequency on the copper windings. Transient current tends to travel on the outside of the copper wire, effectively reducing the cross sectional area of conductor available and therefore increasing resistance of the wire. There's not much you can do about this unless you're planning on rewinding the motor, in which case you might choose many smaller wires run in a parallel bundle to increase the surface area.
> ...


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## NabilAhmad (Feb 26, 2011)

Billduck said:


> The specifications say the drive is rated for 300 amps for an hour. The following is a link to the product data sheet. I have been contact with the Kollmorgen rep, and he may be able to get some electrical schematics. Even for an older drive.
> http://www.kollmorgen.com/website/com/eng/download/document/ACS.pdf
> Bill S


I have a source for several, potentially dozens of these paired with a motor for under a grand. What more information have you been able to find?

Thanks!


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## Billduck (Apr 18, 2009)

I am looking for 2 each, of an 80 volt version of this motor/controller.


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