Possible to make a trapezodial motor run on sinusodial cont?

[Alan B]

I've converted a number of ebikes with trapezoidal type motors to Sinewave Field Oriented Control. They run better on sinewaves in terms of noise, and the controllers have been more reliable than the simple trap controllers that don't really measure motor current and in some cases occasionally have excessive current peaks that damage the FETs. Motor current throttles (torque) which are generally found only on the FOC controllers are also much more driveable.

Trap controllers don't rotate fields smoothly like sinewave FOC controllers do. This leads to small reductions in efficiency as the rotor is not always perpendicular to the magnetic field. Shape of the BEMF waveform itself is not really the issue. This has been measured and documented with various motors in the thread on the Compact FOC controller from Ebikes.ca known today as the PhaseRunner.

https://endless-sphere.com/forums/viewtopic.php?f=31&t=65031

 

[larsb]

Ah, i see. In real life what's compared is your typical cheap chinese trap controller and a more advanced and expensive sine controller.

I find this video interesting, it's actually from user "EG":
https://youtu.be/m3rZCvAX37k
The trap mode on this grin controller might actually be making less noise than the sine - don't you agree? I believe the big blocks are pure trap motors (from memory) so should fit trap driving.

Trap controllers don't rotate fields smoothly like sinewave FOC controllers do. This leads to small reductions in efficiency as the rotor is not always perpendicular to the magnetic field. Shape of the BEMF waveform itself is not really the issue.

As long as position sensing is done through hall sensors then accuracy is the same. The controller just follows it's algorithm between the hall states differently between trap and sine controllers.

FOC is different but then you have a sensorless position sensing algorithm.
(Examples: Powervelocity controllers are not FOC. Kelly KLS is not FOC, they're both just sine)

Check this study on trap vector modulation:View attachment Vectorcontroloftrapezoidalback-EMFPMmachinesusingpseudo-Parktransformation.pdf
The trap controllers can be advanced, what's out there isn't so you're correct in this. Still trap BEMF motor should ideally be fed with trap waveform current.