DIY Electric Car Forums banner
Cancel

AC Motor Selection

94952 Views 28 Replies 14 Participants Last post by  remy_martian, 
xrotaryguy
AC motor selection differs from DC motor selection because AC controllers may require a matching motor. In fact, most AC motors marketed for EVs come with a controller. These controllers often (but not always) include a built-in charger and DC-DC converter. Below is a list of AC motor and speed controller combinations.

Industrial VFDs (Variable Frequency Drives) usually have a smart "learning" feature to configure itself for a particular motor, and can therefore be used almost universally with 3 phase induction motors and in some case permanent magnet synchonous (BLDC) motors.

Some parameters may need to be entered such as:
Base voltage, base frequency, nameplate RPM, max speed, max current, magnetising current, number of poles, encoder pulses per rev, overload rating, and Star or Delta connection. This will allow the VFD to run in a very basic Volts/Hz mode, meaning it can control speed but not torque.

To run in a torque controlling mode, the VFD needs to "learn" (sometimes called "Auto tune") the motor characteristics. The VFD simply spins up the motor with no load on the shaft and generates an electrical model of the motor at various RPMs. Some VFD's can do these measurements on the fly as the motor is running, eliminating the need for Auto tuning. Sensorless vector mode uses Back EMF from the motor to measure motor speed, and control torque. Closed Loop Vector mode uses an Encoder to measure motor speed. The encoder has better accuracy, and enables finer control of speed and torque.


A VFD used in an EV must support vector control (torque control), and have access to the DC bus for connecting to the battery pack. Be aware that the VFD manufacturer may not warranty their product if used in an EV.

MotorControllerContinuous Power (hp/kW)Peak Power (hp/kW)Peak Torque (ft-lbs/N-m)Weight(lbs)/ Mass(Kg)Diameter (In/Cm)Length (Inc/Cm)Voltage Range (rms)Max rpmLink to Manufacturer or Retailer
AC Propulsion T-zeroT-zero?/?268/??/?110/5012in/305mm15in/381mm?/?13,000AC Propulsion
AC Propulsion AC-150AC 150?/?200/?165/225110/50240/45012,000AC Propulsion
Siemens 1PV5135-4WS28?90hp/67kW160hp/120kW317/430200/909.65in/245mm16.7in/425mm460V10,000Siemens
Solectria AC24DMOC44518.77/[email protected]49.6hp/37kw57.66/78.1983.6/38.09.45/24.015.55/39.5?12,000Electroauto
Solectria AC55DMOC44546/[email protected]63.0hp/47kw105/142234.35/?13.5/?16.4/??/?8,000Electroauto
ABB 3GAA 131 003-**EIndustrial VSD15hp/11kW50hp/37.5kW92/125115/5210.3in/260mm14.5in/367mm220V-690V6,000ABB
ABB 3GAA 131 315-**EIndustrial VSD15hp/11kW67hp/50kW122/165170/7710.3in/260mm18.5in/470mm220V-690V6,000ABB
ABB 3GAA 131 316-**EIndustrial VSD20hp/15kW80hp/60kW147/200178/8110.3in/260mm18.5in/470mm220V-690V6,000ABB
ABB 3GAA 131 317-**EIndustrial VSD25hp/18.5kW94hp/70kW203/275210/9510.3in/260mm18.5in/470mm220V-690V6,000ABB
ABB 3GAA 132 004-**EIndustrial VSD12.3hp/9.2kW34.5hp/26kW125/170130/5910.3in/260mm14.5in/367mm220V-690V4,500ABB
ABB 3GAA 132 315-**EIndustrial VSD15hp/11kW52hp/38.5kW192/260183/8310.3in/260mm18.5in/470mm220V-690V4,500ABB
ABB 3GAA 132 316-**EIndustrial VSD20hp/15kW80hp/60kW288/390203/9210.3in/260mm18.5in/470mm220V-690V4,500ABB

Notes For Reading Chart:
All voltages are given in RMS voltage. If you wish to calculate the battery pack voltage necessary, simply multiply the desired or stated RMS value by 1.41 or sqrt(2).
Take the power figures as a guideline only. Most induction motors may be overpowered above their base speed by using a higher pack voltage, extending the constant torque region.
Remember, power (Watts) is the product of torque (Nm) multiplied by speed (rads/s or RPM/9.55). Power figures are stated for the motor's base speed, not the maximum speed.

Notes for Adding Motors:
If you are not comfortable in editing this wiki then post the information in the forums so they can be transferred to here.
These motors are ranked according to their power at their maximum voltage. Statistics would vary using smaller voltages.
I have sourced the information for the Siemens AC induction motor from
http://www.metricmind.com/audi/main.htm
For imperial and metric conversions just google a converter.
Hope you find this useful

External Resources:
Elithion's Motor Driver selection DC, Sepex, Brushless, Induction (July 2012)
Corbin Dunn's AC Motor Selection (April/May 2010)
Cameron Motor Works AC Drive Selection (August 2004)
See less See more
Reply
Save
Like
1 - 20 of 29 Posts
E
The requirement to match a motor to a controller is a sales gimmick.

There are plenty of VFD's that can learn the properties of a motor allowing you to hook up any AC motor to that VFD. Manufacturers of controllers want to sell you a motor and drive combo. Instead of allowing the user to auto tune a motor, type in all the motor parameters and select proper feedback devices, they insist on you just selecting your motor from a list box.

Assuming the controller (VFD) is sized appropriately; allows the user to input motor data or auto tune the motor, and is populated with the correct feedback card (encoder, tachometer...), it should run an AC motor from any manufacturer.
Reply
Save
Like
xrotaryguy
I have seen a couple of chips that are actually designed to learn a motor curve. That's pretty impressive stuff. I guess I could have gone into more detail, but I didn't want to confuse the issue. Generally speaking, the AC motor controllers that most DIYers would be able to use come "pre-matched" so to speak. Most DIY EV builders lack the level technical knowledge required to install a non-EV VFD into an automobile let alone install a set of velocity sensing hall sensors and a reluctor and adapt it all to a random industrial AC motor.

Perhaps we could mention in this article that controllers do not necessarily need to be matched to the motor, but that most EV-specific AC controllers are part of a motor/controller combo to keep installation simple for the DIY EV converter.
Reply
Save
Like
JRP3
Someone might want to add the MES and Brusa motors, or just put a link to the table here: http://www.metricmind.com/motor.htm
Also the lower power HPG motors should be mentioned: http://www.thunderstruck-ev.com/AC_drive_performance.htm
Reply
Save
Like
J
How can I determine Battey Pack voltage for a 15 KW AC motor. Is it as simple as what is stated ie such as 230/460 volts, etc. Can I get an inverter to take me from 96 VDC to 230 VAC and run the motor with decent performance?

Is it all in the windings of the AC motor? The HPGC AC-50 motors run on 96 volts so is it the design of the motor?

JCR
Reply
Save
Like
major
JCR said:
How can I determine Battey Pack voltage for a 15 KW AC motor.
Click to expand...
Hi JCR,

Is it as simple as what is stated ie such as 230/460 volts, etc.
Click to expand...
Not quite. 230 would be the AC voltage for the 3 phase needed at the motor leads. The battery voltage needed to get 230 VAC when inverted would be about 320 VDC. IIRC, VDC = 1.4 times VAC, because you need the VDC to equal the peaks of the AC sine wave.

Can I get an inverter to take me from 96 VDC to 230 VAC and run the motor with decent performance?
Click to expand...
No. Unless you add a boost converter in front of the DC to AC inverter. And that is something you're unlikely to find.

Is it all in the windings of the AC motor?
Click to expand...
Pretty much so.

The HPGC AC-50 motors run on 96 volts so is it the design of the motor?
Click to expand...
Yeah, I guess they have them wound for that.

Regards,

major
See less See more
Reply
Save
Like
JRP3
The HPG motors can run higher than that, not sure how much higher in stock winding, but the Curtis controller they use cuts off at 130 volts.
Reply
Save
Like
J
JRP3 said:
The HPG motors can run higher than that, not sure how much higher in stock winding, but the Curtis controller they use cuts off at 130 volts.
Click to expand...
I see that with the HPGC AC50 motor running on 96 volts you run at 500 amps from out of the gate. Have you seen the motor curves .... I don't get the 500 amp straight line can someone help me out here?

JCR
Reply
Save
Like
JRP3
Are you referring to this chart?
See less See more
Reply
Save
Like
major
JCR said:
I don't get the 500 amp straight line can someone help me out here?
Click to expand...
Hi JCR,

Thanks to JRP3 for posting the curve. It shows the maximum output for the motor and inverter. The "amp" trace is AC motor current. It is proportional to motor torque. So at low speeds, at maximum torque, current is about 550 Amps, AC. But at the low speeds, motor voltage is low. And as the RPM increase up thru 3000, the motor torque and current stay pretty constant. The motor voltage has been increasing as the RPM increase. At around 3000 RPM, the maximum available motor voltage is applied. Beyond 3000 RPM (base speed), the torque decreases as does the motor current because the motor voltage can no longer be proportionally increased.

Realize that this plot shows motor current and battery voltage. Battery current curve shape would resemble the shape of the Horsepower curve.

Hope that helps ya :)

major
Reply
Save
Like
J
major said:
Hi JCR,

Thanks to JRP3 for posting the curve. It shows the maximum output for the motor and inverter. The "amp" trace is AC motor current. It is proportional to motor torque. So at low speeds, at maximum torque, current is about 550 Amps, AC. But at the low speeds, motor voltage is low. And as the RPM increase up thru 3000, the motor torque and current stay pretty constant. The motor voltage has been increasing as the RPM increase. At around 3000 RPM, the maximum available motor voltage is applied. Beyond 3000 RPM (base speed), the torque decreases as does the motor current because the motor voltage can no longer be proportionally increased.

Realize that this plot shows motor current and battery voltage. Battery current curve shape would resemble the shape of the Horsepower curve.

Hope that helps ya :)

major
Click to expand...

Major,

Thank you.

So the yellow line is battery pack voltage at 96 volts and stays about the same. The red line is motor and inverter alternating current and shows that the motor will put out 550 Amps at full torque up to about 3,000 rpms.

Does this mean that if the motor is at 20% max torque the battery current draw will be about 110 amps? And if the motor is at 50% max torque the battery amp draw will be 275 amps and if the motor is at full torque the battery amp draw will be 550 amps. Realizing that the motor alternating current and power both drop after 3,000 rpms. Am I getting this correctly?

Also, from 0-3,000 rpms the battery current draw depends upon torque the motor has to produce for the given load.

JCR
Reply
Save
Like
major
JCR said:
Does this mean that if the motor is at 20% max torque the battery current draw will be about 110 amps? And if the motor is at 50% max torque the battery amp draw will be 275 amps and if the motor is at full torque the battery amp draw will be 550 amps. Realizing that the motor alternating current and power both drop after 3,000 rpms. Am I getting this correctly?
Click to expand...
It has been my experience that at base speed and max torque, AC and DC amps are about equal. But at higher and lower RPM, I don't know a simple relationship for you to use. You probably should revert back to power to figure the DC battery current. Use the motor output power and divide by 0.8 or 0.85 for efficiency to get battery power and then divide by battery volts to get battery current.
Reply
Save
Like
T
major said:
Hi JCR,



Not quite. 230 would be the AC voltage for the 3 phase needed at the motor leads. The battery voltage needed to get 230 VAC when inverted would be about 320 VDC. IIRC, VDC = 1.4 times VAC, because you need the VDC to equal the peaks of the AC sine wave.




major
Click to expand...
Quite different when using H Bridge configuration as drive electronics the way I understood. Actually a lot depends on the voltage control, switching frequency and PWM scheme. I think it best to contact the VSD manufacturer for DC link specifications.
Reply
Save
Like
mizlplix
If it is any help,(on my AC50 system) I too only get a few hundred amps out the gate if I slam the throttle open from dead stop. It then builds up to as much as 586 AMPs (for my set up and pack).

A similar DC set up, If I would slam the throttle open from zero, I would get 400-500 amps momentarily, then begin to fade down to about 280 or so, there I would have to shift up.


Miz
Reply
Save
Like
JRP3
Were you measuring battery amps or motor amps with the DC system?
Reply
Save
Like
G
This maybe a dumb question. I found a website that has low priced ac motors. My question is how do I know if these are good for an ev conversion or build? The website is automationdirect.com any help that you guys could give me would be great.
Reply
Save
Like
mizlplix
There are several threads about this subject and a LOT of different opinions.

There is no readily available way to immediately use one of these industrial motors without a ton of mods or a very special inverter and a very expensive battery pack.

If you are very electrically inclined, you can "bodge" up something and eventually get it running in an acceptable manner. It will take time and money.

1-Rewind motor and use a Curtis controller and a normal battery pack.

2-Use motor as-is and convert a stationary inverter to do vehicle duty and then build a high voltage pack to support it. (shorter range unless you double the pack size)

3-Buy an existing AC vehicle system. Use a normal pack.

I'm sure others will point out my flaws, but this is what I see.

Miz
See less See more
Reply
Save
Like
PStechPaul
GrfxImage79 said:
This maybe a dumb question. I found a website that has low priced ac motors. My question is how do I know if these are good for an ev conversion or build? The website is automationdirect.com any help that you guys could give me would be great.
Click to expand...
I have dealt with www.automationdirect.com and I have found them trustworthy, and their products have been of good quality. I have looked at their motors on their website and they seem to be pretty good, and reasonably priced, especially for new motors. They are most likely Chinese and often it seems that their products have a few flaws which may range from minor to major. If you do buy from them, ask about their warranty to see if it applies to EVs.

I have found lots of good deals on motors on eBay, andI even found a 5HP three phase motor on Craigs List. IMHO you should get a premium efficiency motor, even though it may be bigger and heavier, and try to get a frame type that is easy to mount in your conversion, and which is protected from water and dirt and has a good means of cooling.

Best thing is probably to pick out a few motors that you think will work, and post a thread to ask the experts what they think. :)
Reply
Save
Like
mizlplix
Note to all:

There are two camps in the AC motor subject, High voltage and Low voltage.
Each has it's own talking points. It's own positives and negatives.
I am in the Low Voltage camp.

The single largest cost in the construction of an EV is the battery pack.
In both systems, you use the same cell capacity in the pack (which is set by your daily driving needs.) BUT, in the high voltage system, you need additional cells in series to gain that higher system rating, adding significantly to your build cost and car room to put them.

Another big value component is the controller.

In the Low Voltage system, you have several choices and they are an engineered, tested, finished product.

In the high voltage system, you are limited to two choices, modify an industrial controller or build your own........Both are challenges.(there might be a ready-made unit out there, but I was not able to find one.)

Where I have a decent grasp of electronics, I am not an engineering level Tech, nor do I want to spend money doing R&D perfecting a controller and even then "settling" for a unit that gets me 90% of the control I expect and need.

If and when someone finally "proves" a decent, dependable, high voltage AC controller that even comes close to a Curtis system in quality of operation, I will revisit my position. (even then there's still the Pack cost and room to mount it, to deal with.)

There are few easy to adapt AC industrial motors and the best of the breed, "the inverter duty" ones with an encoder,are expensive.($1500-$3500)

But, to convert almost any AC industrial motor to low voltage is pretty straight forward.

Low motor cost: Use a salvage motor.
Rewind cost: $500-$800.
Encoder= $150

You can get into that custom built motor for the same price or even cheaper than an industrial "Inverter Duty" and an off-the-rack motor.
(I have also found several persons actively rewinding Industrial motors to EV use. Both on the internet and here locally. It is not as easy or mainstream as one would think, but it is being done.)

So, Choices are:

1-More expensive pack-cheaper motor-Amateur made controller of dubious service reliability.
2-Normal cost pack-dependable controller-medium priced (but cheaper than a ready built motor) motor.

In performance and range, the high voltage system wins. But at this writing, that type system is still unreliable.

Miz

(The internet, being what it is today, will yield some nay-sayers to my above opinions, but I still find them valid. It is for each to find what they will settle for or need in vehicle propulsion )
See less See more
Reply
Save
Like
PStechPaul
A few things to consider:

Many standard AC induction motors can be reconnected internally for 138V instead of 240V three phase. These can be overclocked to 100 Hz for 70% greater speed and HP, so a 4 pole 1750 RPM will be about 3000 RPM which is just about right for EVs. And you can usually get 2x to 3x torque for short bursts as needed. And this can be done using a standard motor. For about $800 you can get a nice 30 HP motor and get 52 HP continuous and 150 HP peak. ;)

A standard industrial VF drive rated 30 HP can be had for about $500. Many of these are surplus and still come with warranties. If there is a failure, it will usually be the IGBTs and you can get replacements, perhaps with higher capacity, for about $200/set. :)

It is possible to boost the voltage of a battery pack to a higher voltage as needed by a VFD. So you can use a 144V pack and get 288V with a voltage doubler. For 30 HP at 288V you need 22 kW or 78 amps. You can make an isolated 144-144VDC converter rated 11 kW and add it in series with the battery pack. An 11 kW switching supply could be made for under $500. :cool:

For lower power systems you can get discount laptop batteries for about $0.60/W-Hr. 30 pieces of these will cost about $1000 and will give you 330 VDC and 1.8 kW-Hr, and nominally 5 amps (2.5 HP) or pushing them to 8x you can get 20 HP. If you can achieve 150 W-Hr/mile as I've seen posted, you have about 10 miles range for each $1000 of batteries. :)

That's enough to get started on a project with a total cost of under $2500, and you can always add more batteries to get the power or range you want. Using standard components makes service and replacement simple and inexpensive, and the industrial components are exhaustively tested and backed up by major brand companies. ;)
See less See more
Reply
Save
Like
1 - 20 of 29 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
DIY Electric Car Forums
A forum community dedicated to DIY electric car owners and enthusiasts. Come join the discussion about electric vehicle conversions, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
All EV Conversions and Builds Batteries and Charging Technical Discussion New Member Introductions eBay EV-Related Auctions
Top