IF ALL ELSE FAILS AND IF THE DC MOTOR IS A PERMANENT MAGNET FIELD MOTOR YOU REVERSE IT BY REVERSING THE POSITIVE AND NEGATIVE WIRES TO THE MOTOR. FOR A POWER SUPPLY, UP TO 2 HP, YOU CAN USE A VARIABLE SPEED CONTROLLER BUILT FOR ROUTERS, TYPICALLY LESS THAN $50. ADD A 120 VOLT DC RATED DOUBLE POLE, DOUBLE THROW CENTER OFF SWITCH FOR INSTANT REVERSING WITH OFF. THAT WAY, THE SPEED CONTROL CAN BE LEFT ON AND THE SPEED SETTING UNCHANGED.
IF THE MOTOR HAS A WOUND FIELD, THE REVERSING SWITCH MUST BE WIRED TO REVERSE POLARITY TO EITHER THE FIELD OR THE ARMATURE, AND MUST NOT HAVE A CENTER OFF POSITION, SO AS NOT TO HAVE THE FIELD OR ARMATURE ENERGIZED WHILE THE OTHER IS DIS ENERGIZED. ON/OFF IS DONE AT THE SPEED CONTROLLER POWER SWITCH.
IF THE MOTOR HAS ONLY 2 WIRES, AND WAS REVERSED AT THE CONTROLLER, YOU CAN BE SURE IT IS A PERMANENT MAGNET FIELD MOTOR.
IF IT HAS 4 WIRE, IT IS A WOUND FIELD MOTOR AND IT MAY BE SERIES OR PARALLEL WOUND. A SERIES WOUND MOTOR, AT NO LOAD HAS A VERY HIGH SPEED, LIKE A ROUTER MOTOR. A PARALLEL WOUND MOTOR HAS A NO LOAD SPEED NOT MUCH HIGHER THAN ITS LOADED SPEED.
IT IS MOST LIKELY YOUR MOTOR IS EITHER A PERMANENT MAGNETIC OR PARALLEL WOUND FIELD TYPE.  |