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Discussion Starter · #1 ·
Hello everyone,

I have a 65 kW permanent magnet electric motor with a resolver that says it should be able to produce around ~500 ft/lbs of torque. It came with its own controller/inverter and is completely CAN controlled. The electric motor is directly connected to a driveshaft to a F450 rear differential.

I am having issues getting the vehicle to accelerate, it is extremely de-rated.

At stall/very low speeds, the motor will buck/jerk until you get above a few hundred RPM. When accelerating the inverter will not draw more then 30 amps from the battery (389V nominal battery pack). It will also not go above 1000 RPM's before the inverter will shutdown. Also if I request too much torque the motor will start to jerk and slow down and the inverter will start to heat up quite rapidly. Basically requesting less torque makes it accerate faster.

Also sometimes when I turn on the inverter it will make a loud high pitch noise and will cause the battery to fault out almost immediately if I apply any load. This noise will go away if I key cycle a few times.

What makes this even more strange is that ONE time I was able to get the vehicle to rapidly accelerate, draw AT LEAST 200 amps from the battery, and travel at 1200 RPM's (32 MPH) before I had to stop. As soon as it key cycled it went back to very low power mode.

The inverter is not throwing and faults and always says that it is ready to go which makes diagnosing the issue very tricky.

Any help/suggestions would be greatly appreciated

Thanks!
 

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Welcome,

we would need more information such as motor make and model, inverter make and model or part number, battery pack cells and configuration, fuses, precharge circuit, contactors,etc. in order to get some idea of possibilities. Feel free to lay it all out there, the more details the better for this sort of issue.

One idea off the top may be that the magnets have been demagnitized or damaged by previous overcurrent operation--it's hard to know what a previous owner may have done when messing with stuff.
 

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Discussion Starter · #3 · (Edited)
The electric drive is from Eaton, Siemens, and SR Drives. We have 4 motors and 6 inverters to go with them all of them are prototypes and that is what all the documentation we have for them says. They were never commercially produced and are engineering samples. It was intended for an electric drive for large vehicles. The companies that donated the products are unable to provide support.

If it helps at all the motor is mounted about 4 feet away from the inverter and the phase and resolver cables run that length between the two.

The battery back is from A123 22.8 kWh, made up of 357 prismatic cells in a 119S3P configuration capable of supplying 612 AMPS peak and 180 AMPS continuous. The battery pack is also CAN controlled and it handles all of its contactors, precharging, and ground fault detection.

Let me know what else you need to know about the system.

Thanks
 

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Discussion Starter · #6 ·
The specs are as follows

392V DC nominal input

Motoring Mode
0-1000 RPM 620 NM Peak 340 NM continuous
1000-3200 RPM 65 kW Peak 35 kW continuous

Generation Mode
0-1000 RPM 620 NM Peak 340 NM continuous
1000-3200 RPM 65 kW Peak 35 kW continuous

Performance Graph


Phase Current Ratings


Efficiencies
 

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Hi max,

Symptoms sound like you may have a problem with the resolver. Have you checked the signal coming from it? Sometimes two phases get swapped (connected wrong). Just a SWAG on my part. Good luck. Interested to see your progress.

major
 

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Discussion Starter · #8 ·
That was my thinking as well, that it would be a resolver issue. There are slots on the resolver stationary part to rotate it. I am currently rotating the resolver clockwise by a degree or two and seeing if anything changes.

I am sure that the resolver wiring is correct according to the documentation. The documentation could be wrong though because it is all drafts/prototypes.
 

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If you have an extra motor and inverters available this could be done on the workbench--use a small dc motor to slowly back drive the big 65kW motor and look at the 3 phase waveforms on an oscilloscope to verify that the polarity is correct for the direction of rotation of the inverter, e.g. U,V,W.

In addition if the resolver is excited while this is done, then the resolver output and polarity could be verified, and determine if it is a single or multi-turn resolver.

Does the motor also have a tachometer winding? Does it have any hall sensors?

[edit]

from your motor data posted above, it looks like your motor has a Ke = 5.94 V-s/rad, which means back emf is 621 Volts per 1000 RPM.

So it is a very low speed, high torque motor, and unless that inverter has an internal boost stage, it doesn't seem like you have enough
voltage to run that motor.

And if you could back drive it at 10 RPM, you would likely see about a 6 volt sinusoidal waveform, the amplitude will be proportional to the speed.
 

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Discussion Starter · #10 ·
Last night I step by step incremented the resolver counter clockwise. Every step the peak output increased on the dyno and the motor got smoother. I am able to get the motor to run happily up to ~1300-1400 RPM's (30-35 MPH) but after that it gets unhappy again and will shutdown.

I am thinking that I may need to advance the resolver a little bit more to be able to operate at higher speeds. This vehicle does not need to go much faster than 40 MPH.

The inverter/motor still makes the high pitch screaming noise when powered up occasionally so still open to suggestions on that.

Thanks,
Max
 

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Maybe adjust carrier frequency if you can. See if noise changes pitch. Also try changes in length and position of phase cables.
 

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Discussion Starter · #12 ·
I am unable to change the carrier frequency of the inverter. That is out of my control. Also changing the position of the phase cables has no affect. I am unable to change the length of the cables because of the cost and they are already installed in the vehicle.

What makes the noise issue so weird is after a key cycle or two the noise will go away.
 
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