[Al_The_Man]

I did test the motor and there is voltage at the brushes when it is turned on. The brushes look OK to me. If any one could help I would really appreciate it. I do have a multimeter and I have a simple knowledge of using it. Thank you

I just reread and noticed you mention a voltage at the brushes, so there could be a problem with the motor if it is not turning, another test is to back feed it with another motor source and see if it generates a DC output, the output will be relative to speed, if it is a 90vdc motor at 2000rpm, turning it at 2000 rpm should generate 90vdc.
This applies to a permanent magnet field motor.
Al.

[lclore]

As you make your decision, please note that polarity switching isn't an optimal dc motor control method, especially if its immediate (via DPDT Relay or whatever, with a minimal time delayin contact changeover). It works, but doesn't control the field build up or decay of either a permanent magnent or shunt wound motor. The end result can be a more severe arc when switching which shortens motor life.

Polarity switching of a fixed source voltage also negates accel or decel control and fixes speed (voltage is speed to a dc motor). A regen drive (4 Quadrant as Al mentions) provides accel, decel, variable speed, and better torque control at low speeds. Possible mfg's of these include KB, Baldor (many of the Baldor units are KB), Dart, Minarik, Fincor (now part of Emerson), etc. While I have put a pile of the KB #KBMG212D out there successfully in many automation projects, I am sure any of those manufactures would have a suitable offering.

If you decide to spend the money on a real drive, skip the non-regenerative (2 Quadrant) types. A KB #KBIC120 can be had new for $80... but the performance isn't as nice. Good Luck!!

[KEN BANGERTER]

I STARTED MY INITIAL POST, "IF ALL ELSE FAILS". PLUGGING A DC MOTOR FOR INSTANT REVERSAL REQUIRES A DC RATED SWITCH, A CAPACITOR TO ABSORB THE ARC IS A GOOD REFINEMENT. I HAD USED PLUGGING ON A 3/4 HP PARALLEL WOUND FIELD DC MOTOR, FED WITH 1/2 WAVE RECTIFIED DC AT 90 V WITHOUT ANY TROUBLE USING A SQUARE D REVERSING SWITCH ON A 9 INCH SOUTH BEND LATHE FOR TAPPING, SINCE 1970. NOT IN PRODUCTION BUT USED FREQUENTLY AND STILL GOING STRONG. I RECENTLY REPLACED IT WITH AN INSTANT REVERSING 120 V AC LATHE MOTOR, STILL USING THE ORIGINAL DRUM SWITCH, SO I COULD USE THE DC MOTOR ON AN OTHER APPLICATION.