PicoScope 7 Automotive
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E-Motor Fault Testing
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ashtray1987
- OneWave
- Posts: 48
- Joined: Tue Jul 25, 2017 11:52 am
E-Motor Fault Testing
Hi Guys,
I have been seeing a significant rise in the number of vehicles seeing what appears to be de-magnetization of the rotor in permanent magnet synchronous motors.
This tends to occur on vehicles with high mileages and typically the power electronics reports excessive current demand from the e-motor aswell as a failure of the sensorless speed control.
These motors use a resolver through which a frequency is passed through, the magnetic flux distorts this sine wave and the power electronics uses this to determine position and the condition of the flux.
There are a whole number of white papers on the interweb regarding failure types of these motors, but as yet I haven't found any information regarding real world testing of automotive e-machines.
I see that Pico do sell a three phase current clamp, but I wondered if anyone on here has used this or other techniques to reliable pinpoint faults, specifically to the condition of the rotor/stator assembly?
Appreciate any advice you have.
Thanks
Ash
I have been seeing a significant rise in the number of vehicles seeing what appears to be de-magnetization of the rotor in permanent magnet synchronous motors.
This tends to occur on vehicles with high mileages and typically the power electronics reports excessive current demand from the e-motor aswell as a failure of the sensorless speed control.
These motors use a resolver through which a frequency is passed through, the magnetic flux distorts this sine wave and the power electronics uses this to determine position and the condition of the flux.
There are a whole number of white papers on the interweb regarding failure types of these motors, but as yet I haven't found any information regarding real world testing of automotive e-machines.
I see that Pico do sell a three phase current clamp, but I wondered if anyone on here has used this or other techniques to reliable pinpoint faults, specifically to the condition of the rotor/stator assembly?
Appreciate any advice you have.
Thanks
Ash
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Steve Smith
- Pico Staff Member
- Posts: 1594
- Joined: Sun Aug 25, 2013 7:22 am
Re: E-Motor Fault Testing
Hello Ash and thank you for the post
Most certainly, to qualify motor performance and integrity, current is best and the safest option.
Whist measuring current is desired, it is not always possible to access the phase wiring of the Motor/Generator (MG)
The following forum post has a number of options covered here:
Interesting fault “De-Magnetization” of the Rotor, I assume this requires a new MG assembly?
The ability of the MG to generate a voltage with the stator (or detection coils of the resolver/speed sensor) could be a useful indication of rotor magnetic state?
If we disconnect all phase wiring from the MG, attach PicoScope to the phase wiring, (via a differential probe) then rotate the MG by hand, the voltage levels generated and waveforms obtained would provide an indication of performance.
This of course would require some form of repeatable technique so as to compare apples with apples
I hope this helps and look forward to any feedback
Take care......Steve
Most certainly, to qualify motor performance and integrity, current is best and the safest option.
Whist measuring current is desired, it is not always possible to access the phase wiring of the Motor/Generator (MG)
The following forum post has a number of options covered here:
Interesting fault “De-Magnetization” of the Rotor, I assume this requires a new MG assembly?
The ability of the MG to generate a voltage with the stator (or detection coils of the resolver/speed sensor) could be a useful indication of rotor magnetic state?
If we disconnect all phase wiring from the MG, attach PicoScope to the phase wiring, (via a differential probe) then rotate the MG by hand, the voltage levels generated and waveforms obtained would provide an indication of performance.
This of course would require some form of repeatable technique so as to compare apples with apples
I hope this helps and look forward to any feedback
Take care......Steve