Hi to all,
I have a treadmill motor from a mate that I want to use on my lathe with speed control. It is 180vdc brushed perm mangnet (2 wires only) and 2.5hp continuous rated. I can do the control of speed ok using a pic micro and a pot driving PWM to a FET Driver and then 600v 40A FET without issues and can probably cobble together some kind of feedback for speed stability under load. BTW I'm in the UK and power here is 220vac.
My problem is that the startup current from static on the motor is hundreds of Amps, seeing as the windings are only about 5ohms. The motor is happy to run on unsmoothed full bridge rectified dc and the PWM works as it should but only with a 10 or so ohm resistor in series or the fet would die immediately on startup.
I know that many industrial motors have multiple series resistors that are switched in as needed mainly by mechanical means but I aslo know that on the original treadmill boards this is not how it works. I can't find out how the treadmill boards manage to limit the startup current and there seems nothing on the web about it. Anyone able to help?
Regards, Al
I have a treadmill motor from a mate that I want to use on my lathe with speed control. It is 180vdc brushed perm mangnet (2 wires only) and 2.5hp continuous rated. I can do the control of speed ok using a pic micro and a pot driving PWM to a FET Driver and then 600v 40A FET without issues and can probably cobble together some kind of feedback for speed stability under load. BTW I'm in the UK and power here is 220vac.
My problem is that the startup current from static on the motor is hundreds of Amps, seeing as the windings are only about 5ohms. The motor is happy to run on unsmoothed full bridge rectified dc and the PWM works as it should but only with a 10 or so ohm resistor in series or the fet would die immediately on startup.
I know that many industrial motors have multiple series resistors that are switched in as needed mainly by mechanical means but I aslo know that on the original treadmill boards this is not how it works. I can't find out how the treadmill boards manage to limit the startup current and there seems nothing on the web about it. Anyone able to help?
Regards, Al