Hero999
Banned
No, I'm talking about putting the dimmer ahead of the transformer which will work - it's been done for years with halogen lamps and should work just as well for a motor.
A capacitive filter on the DC side of a 90V transformer is a bad idea because it will increase the RMS voltage to the motor to above 90V.
I think using an isolation transformer is a good idea anyway for safety reasons.
Phase control can be done to reduce the RMS voltage to 90V but it isn't as simple as setting the output to 75% of the full setting. You need to look at the shape of the expected waveform and calculate the required delay for an RMS voltage of 90V.
Another idea is to use a 90V transformer and rectifier with a traditional PWM MOSFET speed control on the output; this will give higher torque at lower speeds but it's not as easy as simply connecting a lamp dimmer before the transformer.
A capacitive filter on the DC side of a 90V transformer is a bad idea because it will increase the RMS voltage to the motor to above 90V.
I think using an isolation transformer is a good idea anyway for safety reasons.
Phase control can be done to reduce the RMS voltage to 90V but it isn't as simple as setting the output to 75% of the full setting. You need to look at the shape of the expected waveform and calculate the required delay for an RMS voltage of 90V.
Another idea is to use a 90V transformer and rectifier with a traditional PWM MOSFET speed control on the output; this will give higher torque at lower speeds but it's not as easy as simply connecting a lamp dimmer before the transformer.