but how to control a dc motor which is shunt wound i.e. with following terminals F1F2, A1A2 i currently use a huge dimmer type dc drive to test these dc motor on cnc machines but i have a GE make DC motor with 4 terminals as named above please tell me how to connect it using your dimmer technique, with your technique i think i need to provide constant dc to field windings F1F2 and connect the dimmer as shown by you to the armature windings A1A2 is it correct if yes then how much voltage should be provided to the field windings?? and how?