“In addition to what others have said, electric motors are happier turning at a higher RPM. Most include a fan which is more efficient spinning faster as well.”
To expand on why this is, motors are referred to as having a “no load speed” for a given drive voltage. Current (and power) are minimum at no-load. With torque loading, current increases proportionally. And power loss to heat in the motor increases with the square of the current. For energy efficiency, we don’t have many choices:
· Choose a motor that has torque/speed curves that fit your load and speed expectations
· Choose a motor that has minimal internal resistance
· Operate as close to no-load speed as possible (minimize torque, maximize speed)
So sure, you can run your motor at ½ no-load speed and avoid a 2:1 gearing. But in doing so, the motor torque requirements will be 2x that you’d need with the gearing. And at 2x the torque, you’d expect 2x the current and 4x the power loss. For a low resistance motor like the ETEK or other permanent magnet motors, the impact may not be that great, but the losses are real and need to be considered.
-MT
No comments:
Post a Comment