DC to 3-PH + VFD Low Speed Torque

[slow-poke]

This question relates to motor conversion on a smaller 10" lathe that has a 1HP DC motor.

I'm curious about the low speed torque of a DC motor vs. a 3-PH motor operating at low RPM via a VFD?

FWIW the VFD will have sensorless vector control enabled that should help the low speed torque.

The present 1HP DC motor has very little torque at very low RPM.

 

[rabler]

This question relates to motor conversion on a smaller 10" lathe that has a 1HP DC motor.

I'm curious about the low speed torque of a DC motor vs. a 3-PH motor operating at low RPM via a VFD?

FWIW the VFD will have sensorless vector control enabled that should help the low speed torque.

It depends on the RPM range over which you are trying to operate. DC motors are inherentlyhave a wider RPM range, VFD driven 3 phase motors are approaching those capabilities but aren't there yet. It is fairly easy to compensate in the VFD system by simply using a bigger motor. I.e., a 2-HP VFD driving 3-phase motor will provide better low speed torque than a 1HP 3-phase motor.

 

[markba633csi]

DC motors can have good low end torque when used with a good controller like KB or Dart

 

[RJSakowski]

The usable speed range on my DC brush motor is better than 50 to 1. I used a custom designed and built PWM control circuit utilizing encoder feedback to achieve this. Torque on my G0602 is actually limited by belt slippage rather than motor stalling.