DC motor with PWM control

[salty]

Hello, My project is to convert a treadmill drive to run a wood lathe. My problem is that as soon as I connect the drive belt the over current indicator light on the circuit board lights up and the motor will run at slow speed for awhile before bogging down making a loud hummming noise. Without the drive belt it runs normal.  I have had the brushed motor apart and cleaned up the commutator on my metal lathe then ran it at high speed ( belt off) for 10 minutes to seat brushes. Voltage to motor without belt is 30 to 85 volts full speed. With belt it starts at 30 will maybe reach 35 before it bogs. I have converted these drives before and one thing different about this system is the lack of choke coil. There is just a short jumper wire in its place. I'm not sure what the choke does but would like to be educated about its use. Also there is a small unit (they call it a reed switch ,pulsing 5V ) that is triggered by a magnet on the original belt drive.
   In other installations I've ignored this and they have worked fine.   Thanks

[mjkuwp]

are you giving it some kind of speed command?  is it possible that simply, the load put on the motor causes it to be over-current and the drive is responding as it should?  You may need to put the reed switch close to the pulley - and of course a magnet in the pulley to give the drive the speed feedback it is expecting. 

What RPM do you need to go?  I guess you know this but a higher belt ratio would be required to keep the current low and voltage high (speed the motor up)

I don't think a choke would affect the motor bogging down or not.  Things like that are used to pass EMI testing.

[WattsThat]

What are specs of the PWM source you’ve purchased?

Typical treadmill motors are rated for 0-120volts dc, perhaps even 150 max at 1000 watts or more so you need to match those voltages and have at least 8-10 amps available to get to those torque and power levels.

Do you have a multimeter?

[salty]

It starts on it's slowest speed and the overcurrent light is on. It will run at this speed for awhile but eventually bogs down. Speed increase will hasten failure. The load  on the unit is a V-belt turning a spindle in good ball bearings, not much compared to an 18 inch belt with a 250 pound person walking on it.
I can try to mount the reed switch but it runs fine without it in a no load situation and on other conversions I have done.
The unit is described as a MC-1000 SCR Motor controller.
The motor is rated at 0 -95 V and when it is run up to full speed (belt off) it develops 85V.
Could there be a weakness in the motor armature windings and how would I test this?
I have a Fluke multimeter