3 phase motor hall effect sensor

[thefamilyman]

Good afternoon gents.

I've got bit of a question about rotation encoding for a PM generator.
I have a 3 phase to DC converter that also is a VFD drive that will be used to start the small diesel motor using the PM generator as a motor.
the problem i have is that the controller needs a 3 phase hall effect sensor to detect rotation and speed which my PMG does not have.
Could i use a novel and reliable way to use the 3 phase AC out of the PM generator in place of a 3 phase hall effect sensor?

[HAL-42b]

I know it has been done, even commercially, but I don't know how to do it 

[Alex Eisenhut]

I'm not sure what you're asking exactly, but it sounds like you want "sensorless" sensing, this is done in low-cost RC stuff, it's part of the controller using the un-energized winding for feedback, but the motor needs to be running for it to work.

Therefore the controller doesn't know which way the motor will spin on power up; this can be dangerous if you can't tolerate a powerful kick in the wrong direction on power up.

[pmbrunelle]

I have used the Timken M15 stuff here:
https://www.anaheimautomation.com/marketing/encoder/rotary-encoders.php

If you can get one to fit (endplay spec is not too good, bore size means that you'll likely need access to the end of the shaft) then it would be pretty inexpensive.

Comes with the three UVW Hall open-collector outputs... pretty idiotproof.

You may need to play with the clocking of the magnet disk and/or PCB to get the right phasing between the rotor and the magnet disk.

Sensorless is interesting, but I think it would have to be built into the drive from the design stage, not added on after.