How to reverse Permanent magnet Syncronous Motor

[JohnDW]

Hi, I need to reverse the rotation of a synchronous permanent magnet motor. We do not have control of the DC to AC (PWM) inverter so cannot simply select reverse in software. As such we would like to attempt to wire the motor and sensors 'backwards' to achieve reverse. The motor is designed to run both forwards and backwards.
The inverter uses 6 IGBTs in 3 half bridges and creates a pseudo sine wave using PWM.The inverter monitors the current draw on each phase and uses a 6 wire resolver to give rotational speed and angle.
We have the ability to;
re-order the phases to the motor.
re-order the 6 firing signals to the inverters IGBT drivers.
Re-wire the resolver or mechanically flip the resolver.
re-order the current sensors.

Three phase systems are defiantly not my area... But is there any reason why we cannot simply reverse parts of the wiring and sensors to make the inverter believe it is running the motor normally but it is in fact revolving backwards?

This is an odd project and we have very few options, changing the inverter or reprogramming it are not possible on this project.

Any help or advice very much appreciated.... if all goes well I will be able to tell you in which publicity stunt this was used. Regards, John.

 

[waross]

Reversing a three phase motor is easy. There should be three power leads. Interchanging any two will reverse the motor. You may have to rewire or flip the resolver for the drive electronics to work properly. Not sure about the current sensors.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[JohnDW]

Thanks Bill,
I've been playing this morning and so far so good.

Swapped phases 2 and 3.
Swapped the signals from current sensors 2 and 3.
Swapped the resolver COS and Sin signals.

At this time the motor is running backwards.
Testing on the Dyno this afternoon...we shall see if the smoke escapes.
John.

 

[electricuwe]

Don't know the power rating of your case, but usually it's preferable to re-order the control signal of the IGBTs.

 

[JohnDW]

Thanks Electricuwe,
The motor is around 80kw max.
When I changed the phases, I did this by moving the control signals and it seems to be working quite well. Now have another software limit to investigate, which is cutting in around half way up the rpm range. J.