How to Control AC 600V PM motor???

[DKirkham]

Hello everyone,

One of our customers has asked us to put an electric motor in one of our cars for him. You can see the cars we make here at out website:

http://www.kirkhammotorsports.com

so you can get an idea of what we are trying to do.

I have searched high and low and I have settled on using the rear electric motor out of a Toyota Highlander. It is cheap, and undoubtedly bullet proof. It comes complete with electric motor and differential as a unit.

I had all the industrial electronic control (CNC stuff) salesmen come by to look at the motor and no one seems able to make it work--let alone even make it move. I then went to the internet and there is precious little information on actually controlling an AC PM motor.

The motor is a 600 volt unit with 8 poles. It has a Hall Effect sensor on it which seems to be one of the sources of our trouble.

We are really fine when it comes to high performance automotive alloy selections, mechanical engineering, and design--but, frankly, electrons are quite mysterious to us, but I am determined to learn, if possible.

Does anyone have any idea on where to point me? Books? Websites? Any help would be greatly appreciated. We prefer to keep the work in house.

 

[itsmoked]

Hi David.

I clearly understand your dilemma.

Re: 400Hz
You are concerned about weight. Justifiably so!

You are disturbed by the weight of the Azure motor (233 pounds). All you need recognize is that an equivalent 400Hz motor would weigh (60/400) x 233 = 35 pounds (call it 50).

That's what I'm trying to get across.


Re: VFD
If it were me I'd screw the hall effect sensor. I would go get an encoder, Heck, I may have two you can use in my storage cabinet. (I bought 3 nice ones and then the job changed.)

Go buy a Vector Drive, hook the encoder up and give it a try. You will need a vector drive with it's DC bus available.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[niallnz]

David,

Can you post the name plate detials of the Toyota motor voltage, current, speed.

The advantage of the 400Hz motor is the power density, it will be smaller than an equivalent 50Hz motor, therfore lighter.

It may be posibble to use a standard VFD on the motor, but you'll have to install a new feedback encoder if the existing hall effect device does not switch the way a VFD expects it to. The motor is from a Hybrid vehicle, engine braking on that car is done via the internal conbustion engine. Regenerative braking on an electric car is limited as the batteries can't accept current as fast as they can deliver it, you may want to have a braking resistor which a standard VFD will be able to control easily.

Standard VFD's are designed for switch rooms and would require modification to work in an automotive environment. Looking at the Azure reference Dan sent their drive is already set up for automotive use. Talk to them about using their VFD on your PM motor.

The local engineering school here has retrofitted a Toyota MR2 with a 25kW 50Hz induction motor and standard VFD. They retained the MR2 automatic transmission and run it selected in low all the time (or reverse). Goes well and looks good, a PM motor would improve starting torque at standstill.

More food for thought??
Cheers Niallnz

 

[DKirkham]

Keith,

Thanks for the continuing help! As you all can probably see, I need it.

If you don't mind, I will contact you tomorrow. I like your encoder idea. I have thought of it before, but no one I found really knew how to do it.

niallnz,

From all I have read, (and my conversations with AC Propulsion--the guys who lent their technology to Tesla), the batteries have no problem taking all the regen you can give them. I, of course, don't KNOW that, just relaying what I have heard. I have thought of the resistor, just in case. I figured I could turn the headlights on as a last resort if all else failed. (We are just talking about prototype stuff right now, NOT, production/customer worthy products.)

I will post pictures of the insides of the motor tomorrow on our website so you can see them. Yes I took it apart! That way I could start asking questions on what all the little parts on my table were and why so many things started falling out! No, actually, I was VERY intrigued by the simplicity of the motor. It is nowhere near as complicated as an internal combustion motor. When I opened the motor, I knew I was looking at the future. I just didn't understand what I was looking at, but I did understand I very much wanted to.

Of course, I found out what a Hall Effect sensor was by taking it off--and losing the orientation! Oh well. You can't learn to swim with out getting wet. I just hope the water isn't full of Great Whites.

Thank you all for your help!

David

 

[itsmoked]

Yeah, no problem. I will check in a few minutes to see what encoders I have.

niallnz; I bet the regenerative braking on the Toyota is limited because they actually have relatively little storage which goes hand-in-hand with low large-current absorption rates. Given a sizable amount of lead acid batteries able to be the primary energy source for 50+ miles I bet you could cram most regen successfully into the batteries.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[DKirkham]

Thanks Keith!

David

 

[davidbeach]

The 400Hz motor may be a blind alley. To gain the size advantage of the 400Hz motor, you would have to have a shaft speed 6.667 times as high as you would with a 60Hz motor. If you are running at 20% of rated frequency, my guess is that the 60Hz motor, with its associated mass, may well turn out to have a better HP/lb ratio. I also don't think the 60/400 ration of weight would pan out either; you may have that ratio of iron in the core (rotor and stator), but you would not have a significant reduction in winding weight, and the shaft wouldn't change at all.

 

[itsmoked]

Hey I added a few pounds to the motor!!

I hear you davidbeach it may not be the full Monty on weight and a gear box may be required. So be it.


DKirkham;
I have a couple of MODEL 220C Hollow Shaft Encoders made by Encoder Products Company, Sand Point, ID

This 220C has been superseded by the 225 which appears to have a higher allowed input voltage 24V verses 15V nothing else matters much.

The 220C s I have look exactly like the pictured "Standard 225A".

http://www.encoder.com/techbulletins/TB-117.pdf

Mine have 400 pulses per revolution
Can turn 4000RPM
Bore size 0.375"
Take 5-15VDC
Consume 25mA
Square wave output
Bidirectional
V+, Common, Shield, Output.

Let me know if you think you can "apply it", and I can shoot you one to try. If it works we can come to some mutual arrangement for a couple.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[sreid]

At one time, Vector Drive VFD's could drive PM AC Motors (Really AC Synchronous Motors). Some drives probably still have this option. It certainly is simple in that the rotor flux has a fixed position. Maybe DV Dick can comment.

For 600 VDC you'll need a drive rated for at least 460 VAC. You would need to figure out how to bypass the input rectifiers.

 

[DKirkham]

I just uploaded some pics of the Toyota Highlander Motor. If you look at the floor in our shop it has 1' x 1' squares on the floor so that will give you a sense of scale.

http://picasaweb.google.com/kirkhammotorsports/ToyotaHybridHighlanderElectricMotor

Keith,

I will try to give you a buzz later. We are in the middle of getting some cars ready for our company track day at

http://www.millermotorsportspark.com

It's a rough job but someone has to do it! If any of you guys are around on the 30th of August, we rented the track and you are welcome to come by for a ride or to drive my car.

sreid,

Thanks for the input! You guys are really knocking the cobwebs off. I haven't looked at this for months and I figured I'd just give you all a try and I am glad I did.

David

 

[ozmosis]

I wouldn't be too happy using standard "vector" PWM drive for a PM motor. Our company are developing this technology to work within a "vector" drive but it's a while off. I noticed WEG had something on a recent fair:

http://www.engineerlive.com/europea...agnet-motors-and-drives-help-save-space.thtml

That is quite interesting. Not sure about their drives but the tech write up is interesting.

 

[itsmoked]

Nice find sed2developer!

Sounds like the ticket. Wonder if they have the kW? Sure be worth hunting down the correct person to ask.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[stephenw22]

I think this idea has TONS of potential.

Do you know what the duty cycle of the motor is? My only worry after looking at that motor is that it seems really small for such a high power rating. I was almost expecting some kind of liquid-cooling pipes in the pictures. But, if the motor is rated for full output power at a 100% duty cycle, that would be awesome.

 

[DKirkham]

sed2developer,

Thanks for the links! I am following them as fast as I can. I see I will have reading material for some days to come. I really appreciate it!

Keith,

I have already sent off an email.

stephenw22,

I think it has tons of potential as well. I am worried about the duty cycle as well. That is one of the reasons I wanted to put 2 of the motors in the car. The Hybrid Highlander manual says you can't take it off road. I assume that is because there is a very small duty cycle on the Highlander rear traction motor (the one in the pictures). The rear traction motor is not connected at all mechanically to the IC engine of the car. It is completely electrical. It kicks in under hard acceleration or when the computer detects wheel slip.

BUT!!!

My Highlander Hybrid weighs around 6000 pounds! It has more pork than Congressman Murtha. The car I want to make should weigh under 2000 pounds ready to go--or be 1/3 the weight. Hopefully we can make it weigh even less. One of our cars we currently make weighs right at 1100 pounds without an engine or transmission (they are extremely light weight). That leaves us 900 pounds for batteries, motors, and incidentals. I think the weight should be easily achievable. If I use two motors at 90 pounds each, then I still have 700 pounds left for batteries (and other stuff) which is way too may batteries.

Now, if the motors still overheat, I can run an oil cooler to the motors as the motor is bathed in oil. Toyota rates the motor at 50KW so you know it can be overdriven somewhat. Their stuff is serious high quality so I am sure I can lean on it.

Now you are all seeing why I saw the writing on the wall with our 25K IC engines when I opened that Toyota motor up and looked inside. It was a very forceful moment in my life--I saw a better way. It may take a few years, but stand alone IC engines are on the road to meet the dinosaurs.

Now, how do I make the dang thing MOVE???

I appreciate all of your help! Thank you so much.

David

 

[Tumppi]

Few facts about PM motors aka brushless ac motors:
It has Permanent Magnet rotor with very strong magnets.
You can not run PM motor with vector drive, even if you have feedback encoder on the motor.
You need encoder/feedback device that can give absolut position of rotor for commutation, when you start running PM motor.
You need a servo drive to make your motor rotate and your thing to MOVE.
But, you should me more worried about how to stop it.
If you rotate PM motor shaft, it acts like generator.
What higher speed motor is running, that higher is the voltage.
Now, worst scenario, you go down hill and your drive trips and your mechanical brakes does not work. What will happen when speed goes higher?

 

[stephenw22]

You could try contacting UQM (

http://www.uqm.com).

They specialize in high-power drives, and might be able to adapt one of their controllers for the Toyota motor. As an alternative, they also make motors with matched controllers, specifically for the automotive industry.

 

[DKirkham]

stephenw22,

I was on the phone with them today. They are checking on it for me. I will let you know. Thanks for the help! We all seem to be going in the same direction and that is good--unless we are lemmings.

David

http://www.kirkhammotorsports.com

 

[DKirkham]

Tumppi,

Thank you for the note. I have thought about stopping the motor. Toyota has somehow solved the problem. I will look further into what they are doing as a fail safe. I do believe, however, it is highly unlikely to have an electrical failure and a mechanical (hydraulic brake) failure at the same time--and certainly most unlikely to have all of that happen on the top of a hill. BUT, you are right. I do need to think of ALL scenarios where gremlins could be hiding waiting to bite me (or worse, one of my customers). I am open to any suggestions you may have. Thank you again!

David

http://www.kirkhammotorsports.com

 

[itsmoked]

Hi DK;
I got no email that I noticed... Resend it maybe? Make sure something logical is in the subject or I could lump it in with the 100 spam I am heaving..

BTW Thanks for the nice pictures! Nice clean looking unit.

You better plan from the git-go to provide serious cooling because as far as I can tell these things run with about a ~20% duty cycle. I rented a Prius just to scope it out for a day. I thrashed it. Near here we have a downhill that's about 3 miles of a lot of braking on a windy country road. The car with about 70% in the storage completely filled the storage after about 1 mile of this road leaving all the rest to the brakes. That led me to the conclusion that the hybrid system is really for idle prevention not prolonged cruising. If I were tasked with that design I would certainly take advantage of the fact that prolonged constant use is not expected.

But it all does come down to temperature. Most things with low duty cycles are limited due to heat. Get rid of the heat effectively and the duty cycle can climb and often rapidly.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[DKirkham]

Keith,

I sent the email again. Who knows what gremlin ate it on my end or your end.

I do agree cooling will be the major problem. I think that is controllable, however. Remember, I have a lot of experience controlling 650 horsepower 500 cid motors. (Tough job I have.)

I am still trying to find the dang manual. Good thing too as I can now see the top of my desk fort the first time in a while.

I will post RPM, volts, wave form, etc as soon as I can find the dang thing. I just posted here on a whim and I am HAPPY I did. I am getting excited about this project again after letting it slide for many months.

David

http://www.kirkhammotorsports.com

 

[fsmyth]

Just to add a bit to the thread, you could use super-caps
for short-term energy dump, and water- or oil-cooled
resistors for longer term dumps that cannot be directed
to the battery bank. T'would seem like a good plan to
include a cooling scheme from the getgo.
I have, in the past, dinked with much smaller 3-phase
BLDC motors, using the Hall devices for positional feedback
and phase current and angle for torque/speed feedback.
Seems to me that it should scale up, possibly using COTS
drives that are inherently designed to run off D.C. only.
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