PDA

View Full Version : Motor data sheets



podolefsky
26 February 2011, 1213
Thought I would get this started. There are a lot of motor data sheets out there, and they all plot performance data differently. There are also some missing pieces.

Here's a datasheet that I constructed from a very fuzzy scan for a D&D ES-15-6. I translated it as best I could into excel.

873

I'll post more soon, then we can try and figure out how to interpret these sheets and actually compare motors.

podolefsky
26 February 2011, 1235
Here is an image with data on 4 popular motors: Mars 0709 (PM), D&D ES-15-6 (series), Agni 95R (PM), and AC-15 (AC). All at 72V.

Mars is plotted over torque (in-lb), as is D&D (made by me). Agni is plotted over Amps, and AC is plotted over RPM (at constant current ???)

http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/motor_sheets.png

podolefsky
26 February 2011, 1347
Here's my first big question, regarding the Agni plot - maybe someone can help me make sense of this. They are running at 72V, and plot over Amps. If you look at the RPM curve, it seems to be saying that as you go from 0-400A, RPM decreases from ~5100 to ~4800.

How can that be? I thought that as you increase RPM, back-emf cancelled the applied voltage and current had to drop (to zero at max RPM). Another way of looking at it is that torque should be proportional to current, and inversely proportional to speed. But this chart makes it look like you can have torque go from 0-50 Nm all at about 5000RPM.

What am I missing?

lugnut
26 February 2011, 1429
Here's my first big question, regarding the Agni plot - maybe someone can help me make sense of this. They are running at 72V, and plot over Amps. If you look at the RPM curve, it seems to be saying that as you go from 0-400A, RPM decreases from ~5100 to ~4800.

How can that be? I thought that as you increase RPM, back-emf cancelled the applied voltage and current had to drop (to zero at max RPM). Another way of looking at it is that torque should be proportional to current, and inversely proportional to speed. But this chart makes it look like you can have torque go from 0-50 Nm all at about 5000RPM.

What am I missing?

I don't think anywhere you'll find that torque is inversely proportional to speed, for motor output characteristics. Maybe in some dream world of a constant power machine :-)

Realize that this plot is a representation of motor performance at a constant input of 72V. It is plotted against current as the x-axis, independent variable. This is done for convenience. Torque opposing rotation of the shaft is the actual independent variable, but because current and torque are in a 1 to 1 relationship, they can be interchanged.

Now then, back to your question. Remember this plot shows the motor at 72V constant at the motor terminals. You have ~5100 RPM at low current (<20A). Then you see 4800 RPM at 400A. The reason the RPM went down is due to voltage decrease reaching the armature to counteract the generated voltage in the armature. The increase in current from 20 to 400A means there is a significant increase in voltage drop between the applied 72V and the actual armature due to the armature resistance and brush voltage drop. This would have to make the actual armature generated voltage about 4 or 5 volts lower, hence a reduction in RPM.

magicsmoke
26 February 2011, 1432
Hi Noah, think of it the other way round. What's happening is that at 72V with 'no load', the motor will spin at 5100RPM and the back emf would equal the applied emf.
An 'ideal' motor would draw no current because of the 'no load'.
However, by definition, a load on the motor has to cause it to slow down which in turn decreases the back emf which in turn causes a current flow. The magnitude of which is proportional to the difference between the applied and the (now lower) back emf. The greater the load, the greater the difference, the greater the current.
In the particular case that a load causes a slowing to 4800RPM, the applied emf (72V) minus the back emf would result in 400A draw.

Rob

podolefsky
26 February 2011, 1611
OK, I'm starting to get what's going on...bear with a poor physicist armed only with V = IR...

At 5100 RPM, bemf = v_applied, so I = 0 with no load. With some load, motor slows to 4800 RPM, bemf is lower, v_applied - bemf > 0 and you get a current flowing. So if your battery/controller are capable, then you could actually get 26 kW out of the motor at 4800 RPM.

So now I'm looking at the D&D data and wondering...at 3760 RPM it reads 92A and 7.1 HP (5300W). Does this mean that if you cranked the current up to 180A, then you would be able to get 10,600 W at 3760 RPM? That would be nice to know, since it would mean at 3C, I could sustain a much higher top speed than I thought. (Even higher if I just did a 450 A burst.)

Nuts & Volts
26 February 2011, 1721
That sounds right. So if you increase the v_applied then you can crank the current up to 180A. The only issues with running higher current at high speeds is bemf and heat. Want more out a given motor? add voltage and cooling. There is a voltage point where the bearings may fail and the motor may arc. Lets point it this way, with super batteries and super controllers you get...

Motor speed limiters - bearings, bemf, arcing, and case construction
Motor torque limiters - wire resistance and thus heat, bemf, and construction*

*Ive read magnets glue may fail at high torque and they can pull out

larryrose11
26 February 2011, 1726
So now I'm looking at the D&D data and wondering...at 3760 RPM it reads 92A and 7.1 HP (5300W). Does this mean that if you cranked the current up to 180A, then you would be able to get 10,600 W at 3760 RPM? That would be nice to know, since it would mean at 3C, I could sustain a much higher top speed than I thought. (Even higher if I just did a 450 A burst.)
no, if you were operating in the current limited region @ lower speed you could.
At the point in question, 3760 RPM, in order to get more current in the motor, you would need to have more voltage available, like something greater than 72V.

The effect of increasing current is best drawn in the 2 AC-15 plots, both at the same voltage. @ 5k ROM, they both produce the same torque, but @ 4k RPM, the torque becomes current limited in the 300 Amp case.

lugnut
26 February 2011, 1732
So now I'm looking at the D&D data and wondering...at 3760 RPM it reads 92A and 7.1 HP (5300W). Does this mean that if you cranked the current up to 180A, then you would be able to get 10,600 W at 3760 RPM?

How do you crank the current up? If you load the motor more, from 92 to 180A, the RPM falls off to about 2800. Otherwise to crank up the current, you must increase the applied voltage.

podolefsky
26 February 2011, 1805
no, if you were operating in the current limited region @ lower speed you could.
At the point in question, 3760 RPM, in order to get more current in the motor, you would need to have more voltage available, like something greater than 72V.

The effect of increasing current is best drawn in the 2 AC-15 plots, both at the same voltage. @ 5k ROM, they both produce the same torque, but @ 4k RPM, the torque becomes current limited in the 300 Amp case.

OK, see that's what I thought. So even though the AC-15 plot says "550A", thats only up until you hit the knee in the torque curve.After that, you're not current limited, your voltage limited. As bemf gets closer to v_applied. you don't have a big enough difference to maintain the full 550A. At 4k RPM, it must be at 300A since the torque is the same in both plots.

On the Agni plot, it's like this - say you're at 5100 RPM with no load (like going down a hill) so no current draw. Then you hit an uphill and if you get on the throttle, you can pull 400A and stay at 4800 RPM with about 35 HP. Is that really what it's saying?

larryrose11
26 February 2011, 1852
On the Agni plot, it's like this - say you're at 5100 RPM with no load (like going down a hill) so no current draw. Then you hit an uphill and if you get on the throttle, you can pull 400A and stay at 4800 RPM with about 35 HP. Is that really what it's saying?
You got it.

podolefsky
26 February 2011, 2332
Now I see why the Agni and AC motors are so sought after. On the basic specs the series motor looks pretty comparable, but now that I understand what happens over the RPM range it's a different story. An AC-15 would pretty much drop right in where my D&D is right now, so time to start saving up...

Coninsan
27 February 2011, 0602
Now I see why the Agni and AC motors are so sought after. On the basic specs the series motor looks pretty comparable, but now that I understand what happens over the RPM range it's a different story. An AC-15 would pretty much drop right in where my D&D is right now, so time to start saving up...

I see you there. I have previously taken the AC-15 capabilities for granted, but I am beginning to understand the power and appeal of the AC motor.
Dialling your AC motor inn, might not be all about getting the reduction right. But more about dialing the maximum current and reduction to provide the power where it's needed.
Further datalogging of the AC motor at specific voltages and current levels would be great.
Praise the wise words being spoken in this thread.

But I have a question based on an observation.
Over at Thunderstruck-ev.com the AC kits 09 through 18 all list the AC-15 motor as the motor used. Is it in fact so that the AC-15 motor itself is capable of operating at 36-108 Volts as listed on the site?

larryrose11
27 February 2011, 1531
Over at Thunderstruck-ev.com the AC kits 09 through 18 all list the AC-15 motor as the motor used. Is it in fact so that the AC-15 motor itself is capable of operating at 36-108 Volts as listed on the site?
Probably. AC moor are pretty robust, anf the performance is largely dictated by the inverter used.

podolefsky
27 February 2011, 1558
Probably. AC moor are pretty robust, anf the performance is largely dictated by the inverter used.

That's what it looks like. It would be easier to know for sure if HPEV ever finished their website.

I looked on Evolveelectrics.com (they're actually here in Boulder). They have the AC-12 / 1238-6501 kit for $2350, but the AC-15/1238-6501 kit is $2950. So either the motors are different, or their pricing is messed up...I'm going to check with them. link (http://www.evolveelectrics.com/High%20Performance%20AC%20Motor.html)

EVparts.com also has the AC-15 kit for $2690 + ~$60 shipping. link (http://www.evparts.com/products/street-vehicle/motors--dot/ac-motor-controller-kits/mt1960.htm)

Coninsan
27 February 2011, 1604
The difference in the AC-12 and the Ac-15 kit is the cost of the controller. The AC-12 kit comes with a 300 Amp controller and the AC comes with a 550Amp. Look-ee here: http://www.thunderstruck-ev.com/index.php?dispatch=categories.view&category_id=36

And the Evolve electrics site pretty much confirms that the AC-15 motor will run up to 108 Volts, super! So a voltage increase doesn't have to mean buying a new motor if you have an AC :)

podolefsky
27 February 2011, 1641
And the Evolve electrics site pretty much confirms that the AC-15 motor will run up to 108 Volts, super! So a voltage increase doesn't have to mean buying a new motor if you have an AC :)

No new motor - just another really expensive controller.

A while back I emailed Electric Motorsport about the AC-20, since the torque listed on their website doesn't match the data sheet (not their fault, seems like every place has this inconsistent rating). Their response was that "we are finding that the PMAC-DS in the field has considerably more Torque and HP then the AC 20 and is 10% more efficient."

That kind of surprised me, especially since the PMAC-DS data sheet (http://www.electricmotorsport.com/store/pdf-downloads/PMAC-DS.pdf) has it at about 85% efficiency, and from what I've found the AC motors are 89% or better.

podolefsky
27 February 2011, 2156
Here's a little piece on AC induction vs BLDC. Sounds like if efficiency is your #1 goal, go BLDC. Induction favors performance with a slight (few %) hit to efficiency.

http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors

larryrose11
28 February 2011, 0441
Here's a little piece on AC induction vs BLDC. Sounds like if efficiency is your #1 goal, go BLDC. Induction favors performance with a slight (few %) hit to efficiency.

http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors
Agreed. All to the hybrids use PMAC drives. because efficiency is the name of the game, and the engine governs the system efficiency.

Personally, I dislike the term BLDC, because these type of motors are not DC, but AC.

The major difference between PMAC and Induction drives that the rotor is magnetized. PMAC motors buys you efficiency in the low speed region before the knee in the Tq-Speed plot. This knee is called Base Speed, and is a characteristic of all motors. In this region, the PMAC drive wins, because you dont have to spend energy to make a field, as you do in the Induction drive. This comes back to bite the PMAC drive at higher speed, because in order to go faster, you have to spend energy to beat down the back-EMF.

If you spend all your operations time at high speeds, the Induction drive can have an advantage, because of the lack of PM material present.

All of these variables can change depending on how the motor was wound, and your system voltages. Yates uses a PMAC drive, but he also has a 377 volt system. This higher voltage extends base speed pretty high, and probably doesn't use the motor to its full capability. Take a look at the tq-speed plot for the QUM 125 @340 V
888
Yates setup is about 377V nominal, the difference is going to shift the 2500ROM knee to the right to about 2700 RPM. Further, he might clip torque to 250 NM by clipping current, so he doesn't flip. These two actions, clipping current and upping voltage puts the knee at about 4700 RPM.

"... Any of this getting through to ya son??'' - Foghorn Leghorn

Nuts & Volts
28 February 2011, 0932
Yea what he said ^^^. I would like to add that the induction motor is also less efficient due to the extra resistive (I^2*R) losses in the induced rotor currents. The term BLDC is used to the describe a motor with a trapezoidal BEMF. A PMAC motor will have a sinusoidal BEMF.

Also the knee described as base speed by larry is a function of BEMF.

One more for reference I think Yates is using the UQM 145

podolefsky
28 February 2011, 0944
The major difference between PMAC and Induction drives that the rotor is magnetized. PMAC motors buys you efficiency in the low speed region before the knee in the Tq-Speed plot. This knee is called Base Speed, and is a characteristic of all motors. In this region, the PMAC drive wins, because you dont have to spend energy to make a field, as you do in the Induction drive. This comes back to bite the PMAC drive at higher speed, because in order to go faster, you have to spend energy to beat down the back-EMF.

If you spend all your operations time at high speeds, the Induction drive can have an advantage, because of the lack of PM material present.

All of these variables can change depending on how the motor was wound, and your system voltages. Yates uses a PMAC drive, but he also has a 377 volt system. This higher voltage extends base speed pretty high, and probably doesn't use the motor to its full capability. Take a look at the tq-speed plot for the QUM 125 @340 V

Yates setup is about 377V nominal, the difference is going to shift the 2500ROM knee to the right to about 2700 RPM. Further, he might clip torque to 250 NM by clipping current, so he doesn't flip. These two actions, clipping current and upping voltage puts the knee at about 4700 RPM.

"... Any of this getting through to ya son??'' - Foghorn Leghorn

Gettin through...thanks!

I understand how back-emf plays in, but not sure I understand your statement about having to "beat down" the back emf at high RPM. I thought there was always a back-emf if the motor is spinning. As RPM increases, it gets closer to v_applied so you can't pull as much current, hence less torque. That's my understanding from DC - PMAC is harder to understand since it's not simply a magnet spinning inside a regular coil. The coils are powered in a sequence...I guess I need to stare at some diagrams to figure out how the back-emf works for PMAC.

And just to make sure I've got this straight - in an AC induction motor, the speed is controlled by the output frequency of the controller, and the RPM limit is based on how fast it can spin before the armature comes apart. It's not back-emf limited like a DC motor.

podolefsky
28 February 2011, 0954
Yea what he said ^^^. I would like to add that the induction motor is also less efficient due to the extra resistive (I^2*R) losses in the induced rotor currents. The term BLDC is used to the describe a motor with a trapezoidal BEMF. A PMAC motor will have a sinusoidal BEMF.

Thanks for the extra clarification.


Also the knee described as base speed by larry is a function of BEMF.

I think the knee is a function of current limit. Limiting the current will move the knee to the right, as Larry said. The overall torque curve is a function of the RPM/V rating of the motor...BEMF is a function of RPM. Increasing RPM/V rating will move the whole torque curve to the right.

lugnut
28 February 2011, 1007
I understand how back-emf plays in, but not sure I understand your statement about having to "beat down" the back emf at high RPM.

The BEMF is a function of both the RPM and Flux. So what I think he meant was to field weaken the motor by reducing the flux or altering the commutation angle (in the PM motor).



And just to make sure I've got this straight - in an AC induction motor, the speed is controlled by the output frequency of the controller, and the RPM limit is based on how fast it can spin before the armature comes apart. It's not back-emf limited like a DC motor.

In all motors, the rotation frequency (RPM) is linked to the electrical frequency. If you have a commutator on the motor shaft, it takes care of this synchronizing the elect and mech frequency. With AC motors, IM, PMAC, BLDC, the commutation is done external to the motor with the source, be it the AC mains or an inverter. The speed of the AC motor (RPM) is dictated by the applied electrical frequency. With synchronous motors, PMAC & BLDC, it is directly proportional. With induction motors (IM), which are asynchronous, there is a slip factor which subtracts from the direct proportionality of electrical to mechanical frequency.

However, although the RPM is dependent on electrical frequency, the AC motor must have the proper voltage applied for that particular frequency to function properly, meaning the efficient production of torque. This is why the inverters used to drive AC motors are Variable Voltage Variable Frequency, VVVF.

frodus
28 February 2011, 1012
And for the AC15/AC20 guys on here with respect to the Curtis controllers.....

If you're going to buy a NEW setup, order either the AC20 or the AC15 with the 1238-7501 controller, not the 6501. It goes to 130V max (meaning your pack voltage fresh off the charger should not exceed this, which is about 34 cells IIRC). If you have the 6501, the max voltage is 108V fresh off the charger. My setup is the AC15 with 1238-7501 controller and 32s6p (if I can fit em in there). The extra voltage extends the torque out to a higher RPM..... quoting Richard Hatfield (No he's not using this on his TTXGP bike).

Oh, and the AC12 is really an AC09 motor with the 6501 controller. There are the AC09 (just over 9"), the AC15 (almost 11") and the AC20 (about 12.5"). I'll stop there beause anything above the AC31 is a bit large for a motorcycle.

Coninsan
28 February 2011, 1020
The extra voltage extends the torque out to a higher RPM.....

By how much does the knee extend by added voltage?
From say your standard 72 volts up to 96 volts.

frodus
28 February 2011, 1027
I don't know, he said it pushes it out further but I don't have a dyno.

podolefsky
28 February 2011, 1047
In all motors, the rotation frequency (RPM) is linked to the electrical frequency.

Not sure what you mean by electrical frequency here - a DC motor will run off of a constant DC voltage. The commutator switches the current direction in the armature. But, as I understand it, the only external frequency involved is if you have a PWM signal which effectively varies the current seen by the motor. It doesn't change the frequency, just the pulse width.

Otherwise, I see what you're saying and it makes sense.

Nuts & Volts
28 February 2011, 1106
I think the knee is a function of current limit. Limiting the current will move the knee to the right, as Larry said. The overall torque curve is a function of the RPM/V rating of the motor...BEMF is a function of RPM. Increasing RPM/V rating will move the whole torque curve to the right.

Current limiting moves the knee to the right because you move to a lower torque output. I am saying that you can extend the knee at maximum torque by increasing supply voltage.

The slope of the curve after the knee is a function of BEMF. Everything before the knee (constant current, constant torque) is simply a function of battery and controller maximum currents and motor thermal limits.

Once you reach the point at which applied voltage equals BEMF you have to field weaken as stated. This uses some of the flux from the current to fight the magnetic field from the permanent magnets. This lowers torque and lowers the BEMF. Essentially you are using current to increase the RPM (read about it all herehttp://web.mit.edu/scolton/www/SCThG.pdf or look up Field Oriented Control, or dq control)

lugnut
28 February 2011, 1123
Not sure what you mean by electrical frequency here - a DC motor will run off of a constant DC voltage. The commutator switches the current direction in the armature.

With the commutator DC motor, the electrical frequency I speak of is in the armature conductors which are connected to the commutator. If you look at the current in an armature conductor (or coil), it will in fact be an AC waveform if the armature is rotating in the DC motor. The commutator/brush assembly is actually a mechanical inverter for the armature coils.

Except for the rare case of the homopolar motor, all motors are AC when looking at the armature :-)

ps....And the electrical frequency I talk about is the frequency of current reversals, not PWM.

Nuts & Volts
28 February 2011, 1127
By how much does the knee extend by added voltage?
From say your standard 72 volts up to 96 volts.

I am fairly certain that supply voltage and base speed are fairly linearly related. This can be seen with the agni which has a constant 71RPM/V. Yes you are discussing AC, but if you arent limited by anything else (controller or battery) at higher RPM it should be linear. So if base speed is 3000RPM at 72 V it can estimated to be around (3000/72 * 96) 4000RPM at 96V.

podolefsky
28 February 2011, 1142
Current limiting moves the knee to the right because you move to a lower torque output. I am saying that you can extend the knee at maximum torque by increasing supply voltage.

The slope of the curve after the knee is a function of BEMF. Everything before the knee (constant current, constant torque) is simply a function of battery and controller maximum currents and motor thermal limits.

Once you reach the point at which applied voltage equals BEMF you have to field weaken as stated. This uses some of the flux from the current to fight the magnetic field from the permanent magnets. This lowers torque and lowers the BEMF. Essentially you are using current to increase the RPM (read about it all herehttp://web.mit.edu/scolton/www/SCThG.pdf or look up Field Oriented Control, or dq control)

I agree with everything you say. For a given motor, the knee moves around based on peak current and voltage. Lowering peak current moves it to the right basically because of geometry - you're chopping the graph lower, but it's not performing any better (actually worse). Increasing voltage actually increases performance.

What I was saying is that if you compare two different motors, they can have different knees for the same current and voltage. That's one reason the AC-15 seems so much nicer than my series motor - at 500A and 72V, the knee for my series motor is at about 1600RPM. For the AC-15, it is at 2500. Also, on my series, torque drops to near zero above 4000 RPM, on the AC-15 it is still about 17 ft-lb up to 6000 RPM. So you can gear lower for the same top speed and have much higher performance.

Also because of this, HP of the AC at 4000RPM is about 5x that of my series motor (for the same voltage).

Only way my series motor is superior is that it will hit close to 80 ft-lb at 0 RPM...and it's a lot cheaper.

Nuts & Volts
28 February 2011, 1145
I agree with everything you say. For a given motor, the knee moves around based on peak current and voltage. Lowering peak current moves it to the right basically because of geometry - you're chopping the graph lower, but it's not performing any better (actually worse). Increasing voltage actually increases performance.

What I was saying is that if you compare two different motors, they can have different knees for the same current and voltage. That's one reason the AC-15 seems so much nicer than my series motor - at 500A and 72V, the knee for my series motor is at about 1600RPM. For the AC-15, it is at 2500. Also, on my series, torque drops to near zero above 4000 RPM, on the AC-15 it is still about 17 ft-lb up to 6000 RPM. So you can gear lower for the same top speed and have much higher performance.

Also because of this, HP of the AC at 4000RPM is about 5x that of my series motor (for the same voltage).

Only way my series motor is superior is that it will hit close to 80 ft-lb at 0 RPM...and it's a lot cheaper.

Cool, glad to be on the same page. FYI that thesis I listed is a great intro to understanding motor performance and motor control. Had to read through twice to fully understand

podolefsky
28 February 2011, 1145
With the commutator DC motor, the electrical frequency I speak of is in the armature conductors which are connected to the commutator. If you look at the current in an armature conductor (or coil), it will in fact be an AC waveform if the armature is rotating in the DC motor. The commutator/brush assembly is actually a mechanical inverter for the armature coils.

Except for the rare case of the homopolar motor, all motors are AC when looking at the armature :-)

ps....And the electrical frequency I talk about is the frequency of current reversals, not PWM.

Right, got it. I love semantics...

podolefsky
28 February 2011, 1149
And for the AC15/AC20 guys on here with respect to the Curtis controllers.....

If you're going to buy a NEW setup, order either the AC20 or the AC15 with the 1238-7501 controller, not the 6501. It goes to 130V max (meaning your pack voltage fresh off the charger should not exceed this, which is about 34 cells IIRC). If you have the 6501, the max voltage is 108V fresh off the charger. My setup is the AC15 with 1238-7501 controller and 32s6p (if I can fit em in there). The extra voltage extends the torque out to a higher RPM..... quoting Richard Hatfield (No he's not using this on his TTXGP bike).

Oh, and the AC12 is really an AC09 motor with the 6501 controller. There are the AC09 (just over 9"), the AC15 (almost 11") and the AC20 (about 12.5"). I'll stop there beause anything above the AC31 is a bit large for a motorcycle.

Easy question here (compared to rest of this thread): the 7501 is rated 72-96V. I know this is a nominal rating, so you can exceed it to 108V. Can you also go under 72? For example, my pack rating is 76 nom, and occasionally sags below 72V. Will this cause the controller to cut out, or will it be fine?

teddillard
28 February 2011, 1158
awesome thread! I just wanted to repost that link, it got muckled:
http://web.mit.edu/scolton/www/SCThG.pdf

frodus
28 February 2011, 1216
I agree with everything you say. For a given motor, the knee moves around based on peak current and voltage. Lowering peak current moves it to the right basically because of geometry - you're chopping the graph lower, but it's not performing any better (actually worse). Increasing voltage actually increases performance.

What I was saying is that if you compare two different motors, they can have different knees for the same current and voltage. That's one reason the AC-15 seems so much nicer than my series motor - at 500A and 72V, the knee for my series motor is at about 1600RPM. For the AC-15, it is at 2500. Also, on my series, torque drops to near zero above 4000 RPM, on the AC-15 it is still about 17 ft-lb up to 6000 RPM. So you can gear lower for the same top speed and have much higher performance.

Also because of this, HP of the AC at 4000RPM is about 5x that of my series motor (for the same voltage).

Only way my series motor is superior is that it will hit close to 80 ft-lb at 0 RPM...and it's a lot cheaper.

you're using an outdated datasheet it seems (pardon me if I'm wrong, but I've got an excel from HPEVS that shows differently). I have a graph that shows ~82ftlbs at 0RPM and it goes out to 1750 before decreasing. This is for 72V and 550A, and peaks ~30HP. The HP is higher for 96V, but I don't have a graph of that.


Motor Motor Motor Motor Motor Motor
Speed Torque Torque Torque Power Power
[RPM] [lb-in] [lb-ft] [N-m] [HP] [kW]
50 978 81.5 110.5 0.8 0.6
250 978 81.5 110.5 3.9 2.9
500 978 81.5 110.5 7.8 5.8
750 983 81.9 111.1 11.7 8.7
1000 984 82.0 111.2 15.6 11.6
1750 985 82.1 111.3 27.3 20.4
2000 929 77.4 105.0 29.5 22.0
2250 810 67.5 91.5 28.9 21.6
2500 696 58.0 78.6 27.6 20.6
3000 523 43.6 59.1 24.9 18.6
4000 324 27.0 36.6 20.6 15.3
5000 217 18.1 24.5 17.2 12.8
5500 183 15.3 20.7 16.0 11.9
6000 156 13.0 17.6 14.9 11.1
6500 120 10.0 13.6 12.4 9.2

frodus
28 February 2011, 1216
Easy question here (compared to rest of this thread): the 7501 is rated 72-96V. I know this is a nominal rating, so you can exceed it to 108V. Can you also go under 72? For example, my pack rating is 76 nom, and occasionally sags below 72V. Will this cause the controller to cut out, or will it be fine?

Yes, you can set the low voltage cutoff. I wouldn't try to run a 72V controller at 48V though, I think there are limits.

podolefsky
28 February 2011, 1231
you're using an outdated datasheet it seems (pardon me if I'm wrong, but I've got an excel from HPEVS that shows differently). I have a graph that shows ~82ftlbs at 0RPM and it goes out to 1750 before decreasing. This is for 72V and 550A, and peaks ~30HP. The HP is higher for 96V, but I don't have a graph of that.


Motor Motor Motor Motor Motor Motor
Speed Torque Torque Torque Power Power
[RPM] [lb-in] [lb-ft] [N-m] [HP] [kW]
50 978 81.5 110.5 0.8 0.6
250 978 81.5 110.5 3.9 2.9
500 978 81.5 110.5 7.8 5.8
750 983 81.9 111.1 11.7 8.7
1000 984 82.0 111.2 15.6 11.6
1750 985 82.1 111.3 27.3 20.4
2000 929 77.4 105.0 29.5 22.0
2250 810 67.5 91.5 28.9 21.6
2500 696 58.0 78.6 27.6 20.6
3000 523 43.6 59.1 24.9 18.6
4000 324 27.0 36.6 20.6 15.3
5000 217 18.1 24.5 17.2 12.8
5500 183 15.3 20.7 16.0 11.9
6000 156 13.0 17.6 14.9 11.1
6500 120 10.0 13.6 12.4 9.2

That looks like the data for the AC-12:

http://hpevs.com/images/stories/AC12_chart.png

But it wouldn't surprise me if HPEV had something different in the excel file for the AC-15...their site is seriously in need of some clean up.

podolefsky
28 February 2011, 1234
Yes, you can set the low voltage cutoff. I wouldn't try to run a 72V controller at 48V though, I think there are limits.

Cool. I'll check the Curtis manual...as long as you can set the low V cutoff to 60V, then it'll work with my pack. Nice to know I could start with my 72V pack, upgrade the motor, then be able to upgrade the pack later on.

frodus
28 February 2011, 1250
Oh, yeah, sorry, i screwed up. that is the AC12. I asked for more curves, but they're kinda shy about giving them out.

I've got a PDF showing 80ftlbs, but not sure what voltage. It peaks at 18hp, so I think its likely for 48V. Also says something about 650A, which leads me to believe its the lower voltage higher amperage curtis.

They really need more info online.

Coninsan
28 February 2011, 1327
Oh, yeah, sorry, i screwed up. that is the AC12. I asked for more curves, but they're kinda shy about giving them out.

I've got a PDF showing 80ftlbs, but not sure what voltage. It peaks at 18hp, so I think its likely for 48V. Also says something about 650A, which leads me to believe its the lower voltage higher amperage curtis.

They really need more info online.

What doesn't make sence to me is that the AC-15 readout listed earlier in this thread, lists a max of 62 ft-lbs at 72 volts, while the readout the Frodus is refering to pushes 82 ft-lbs at 48 volts..

A Elmoto dyno would be a good investment to get these readouts right..

podolefsky
28 February 2011, 1359
What doesn't make sence to me is that the AC-15 readout listed earlier in this thread, lists a max of 62 ft-lbs at 72 volts, while the readout the Frodus is refering to pushes 82 ft-lbs at 48 volts..

A Elmoto dyno would be a good investment to get these readouts right..

I'd assume they're feeding more current to the AC-12 in that graph. Up to the knee, current determines torque, not voltage. Voltage only moves the knee to higher RPM. (Assuming I've learned anything from this thread...)

frodus
28 February 2011, 1653
It apears that both motors are maxing out the controllers. Hence the Flat peak on torque. The torque for these motors apear limited to controller current. I'd guess both are at 550A, but at what voltage?

The huge problem is, that the setups are not labeled correctly. There's no consistancy in their measurements, data or how they display it..... One reason i decided to start testing batteries.


I think the curve for the 62ftlbs is off. I remember the spec being 80+ftlbs. I don't think a smaller motor in the same diameter would have more torque than a longer motor of the same diameter. Just doesn't make sense.

larryrose11
28 February 2011, 1839
The term BLDC is used to the describe a motor with a trapezoidal BEMF. A PMAC motor will have a sinusoidal BEMF.

Trapezoidal BEMF?
Word.

podolefsky
28 February 2011, 1846
It apears that both motors are maxing out the controllers. Hence the Flat peak on torque. The torque for these motors apear limited to controller current. I'd guess both are at 550A, but at what voltage?

The huge problem is, that the setups are not labeled correctly. There's no consistancy in their measurements, data or how they display it..... One reason i decided to start testing batteries.


I think the curve for the 62ftlbs is off. I remember the spec being 80+ftlbs. I don't think a smaller motor in the same diameter would have more torque than a longer motor of the same diameter. Just doesn't make sense.

Yeah, their spec sheets are all whack. Ac-15 is labeled 72V, AC-20 is 48V, and AC-12 doesn't say. But it has way more torque than the other two, which I agree doesn't make any sense since a) the AC-15 is longer, and b) the 15 and 20 kits come with a higher current controller (I believe).

On the AC motor specs, I've noticed that everyplace lists the AC-15 at like 90 ft-lb, and the AC-20 at 110, but these don't match the data sheets. I emailed EMS to inquire and they basically said yeah, we're getting new specs from our supplier...stay tuned. That was about a month ago...things apparently move slowly in the AC induction world...

That's basically why I started this thread. If the motor suppliers are all over the place, maybe we can start to make sense of it ourselves...somehow.

Nuts & Volts
28 February 2011, 1857
Trapezoidal BEMF?
Word.

Yea i learned all that from the thesis i linked. Well tried to link, see Teds post for a proper link.
He stated that a motor has trapezoidal BEMF waveform or sinusoidal BEMF waveform (ie if you speed the motor by hand and o-scope a phase or two you should see a wave like the one described). Then he stated that you can drive either motor with a 6-step/square wave inverter or a sinusoidal inverter with varying results.

I sounded like BLDC motors can offer a higher torque but are less efficient than PMAC (sinwave) motors. As a sinwave motor with a sinwave inverter will offer the smoothest operation.


Noah a few no load tests can give us a rough idea of the motor constants (RPM/Volt) or if someone could measure the BEMF that could be used as well. Then you could get a rough estimate mathmatically of the performance (within 10% i would think).

larryrose11
28 February 2011, 1902
I think the curve for the 62ftlbs is off. I remember the spec being 80+ftlbs. I don't think a smaller motor in the same diameter would have more torque than a longer motor of the same diameter. Just doesn't make sense.

Sure it does. They could just be wound differently. Different amount of turns in the coil windings will yield a different motor KV (rpm/volt) A higher number of turns in a motor will usually provide more torque @ lower speed. but the top speed will be lower. The lower number of turns in a motor will usually provide more top speed, but torque per amp (N-m/A) Peak power could be the same, bu they would occur it different RPM, and hence different torque.

podolefsky
28 February 2011, 1914
Sure it does. They could just be wound differently. Different amount of turns in the coil windings will yield a different motor KV (rpm/volt) A higher number of turns in a motor will usually provide more torque @ lower speed. but the top speed will be lower. The lower number of turns in a motor will usually provide more top speed, but torque per amp (N-m/A) Peak power could be the same, bu they would occur it different RPM, and hence different torque.

That could be - if you compare the AC-12 and AC-15 curves, he 12 has higher torque down low, but on the 15 the torque curve falls off slower toward the high end. So maybe they are trading low-end torque for high-end in the 12, vise versa in the 15.

lugnut
28 February 2011, 1958
- if you compare the AC-12 and AC-15 curves,

A word of caution. Published motor curves and data are notorious for being inaccurate, ambiguous and misleading as well as just plain crap. The only way to know for sure is to test the product for yourself, and then you never know if they will change the design before the next time you buy one :-( In today's market, you buy the motor by the part number, not the performance spec.

podolefsky
28 February 2011, 2114
I edited lugnut's statement down to the essentials:


data are notorious for being inaccurate, ambiguous and misleading as well as just plain crap.

See, when I was looking for motors I compared every piece of data I could, I read all the EV forums. I found a thread for the GPR-S where people were directly comparing the Mars, Sepex, and AC versions. People were getting better performance from the Mars, but then it sounded like the weak point was the batteries...then with better batteries, people were saying the AC felt soft off the line, Sepex actually felt quicker. Then I emailed [edit] Thunderstruck and they said don't get the Sepex, it's flaky and regen isn't worth it, but if I want good regen and performance get an AC. But actually a Mars motor is over 90% efficient, so get that. But really, the Agni is the best performing motor in it's class...but the Mars is just as good for 1/2 the cost...except it's not...

That's when my head exploded and after I scraped my brains off the ceiling, I was ready to buy a series motor and Alltrax. Done, bike is running, I'm having fun.

[edit] This is clearly a rant stemming from too much stress at work and reliving the woe that was choosing a motor. Actually, folks from Thunderstruck and EMS were really helpful...but sometimes too much information isn't a good thing.

larryrose11
02 March 2011, 0805
And for the AC15/AC20 guys on here with respect to the Curtis controllers.....

If you're going to buy a NEW setup, order either the AC20 or the AC15 with the 1238-7501 controller, not the 6501. It goes to 130V max.

You got me all excited about that, and so I contacted Curtis instruments directly. A rep, (Joseph Lewis, MBA) told me:
'The official Curtis datasheet says 72-96 volts. If you were to use a 108 volts system fully charged would most like exceed the over voltage cut off for the controller. 130 volts is the overvoltage cutoff.'
I wish I could talk to an EE, and not an MBA.

"Where'd you get your information from huh?" - Beastie Boys

podolefsky
02 March 2011, 0844
I wish I could talk to an EE, and not an MBA.

I just talked to the Google.

I found the info on p. 55 of the Curtis AC controllers manual. It's a little screwy because on their datasheet (http://www.curtisinstruments.com/index.cfm?fuseaction=cProducts.DownloadPDF&file=50175%5F1238R%5FRevD2%2Epdf) they say the 7501 is 72-96V, and here they list 80-108.

894

frodus
02 March 2011, 0959
Back when there wasn't a 7501, I talked to Brian Hall at Thunderstruck, and then to Brian or Bill at HPEVS (formerly Hi Performance Golf Cars), and they told me that the most you could put into a curtis 6501 was 108V. That is the overvoltage cutoff they had to use for one of their bikes. The 7501 moves that up to 130V. I've only ever confirmed the 130V from curtis instruments. The 105 versus 108V for the 72V controller, I'm not sure, but that seems to be the consensus. Maybe call HPEVS or curtis.

I wish a part number was thrown on that table...

podolefsky
02 March 2011, 1011
I wish a part number was thrown on that table...

The manual is for the 1234/1236/1238. I just posted a quick snip of p. 55. The full manual is here (http://www.thunderstruck-ev.com/Manuals/1234_36_38%20Manual%20Rev%20C2.pdf).

On a quick scan, it's hard to figure out exactly which models these are...I just assumed they meant any 48-80V controller (so 1236-6301 or 1238-6501), and that 80-108V was for the 1238-7501.

podolefsky
04 March 2011, 0907
OK, so I got this datasheet (http://www.electricmotorsport.com/store/pdf-downloads/AC_Drives/AC15.pdf) from EMS. It has the same charts from earlier in this thread, but there is a data table as well and it doesn't match the charts. It shows peak torque of ~80 ft-lb, but peak HP of ~18 HP.

Torque rating kind of makes sense since it is at 650 A instead of 550. But the torque curve (and therefore HP) falls off a lot faster than in the charts. I thought maybe this is lower voltage, but everything else in the doc is at 72V. So this chart makes the AC seem only marginally better than my series motor.

At any rate, none of these match the spec here (http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac15.php) of 43 HP and 95 ft-lb peak.

So...??? Maybe this is why EMS told me they like the PMAC-DS better than the AC.

podolefsky
04 March 2011, 1316
:rolleyes:
OK, so I got this datasheet (http://www.electricmotorsport.com/store/pdf-downloads/AC_Drives/AC15.pdf) from EMS. It has the same charts from earlier in this thread, but there is a data table as well and it doesn't match the charts. It shows peak torque of ~80 ft-lb, but peak HP of ~18 HP.

Torque rating kind of makes sense since it is at 650 A instead of 550. But the torque curve (and therefore HP) falls off a lot faster than in the charts. I thought maybe this is lower voltage, but everything else in the doc is at 72V. So this chart makes the AC seem only marginally better than my series motor.

At any rate, none of these match the spec here (http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac15.php) of 43 HP and 95 ft-lb peak.

So...??? Maybe this is why EMS told me they like the PMAC-DS better than the AC.

Got an answer to my question from EMS - the table is at 48V, the graphs are at 72V. :rolleyes: