a device for changing the direction of the shaft rotation in an electric motor. Reversal is accomplished by changing the direction of the current in the armature winding or exciting winding in DC motors and by phase inversion in the stator winding in AC motors. Structurally, there are two kinds of electrical reversers, drum and cam, in which the switching of electrical circuits is performed by finger-type (sliding) or cam-type contacts, respectively. The contacts are rated according to the current and the power-circuit voltage; they do not have arc-quencher systems because reversal—the change in the direction of a motor’s rotation—takes place when there is no current in the motor’s power circuit.
Electric reversers have two positions: forward and backward in the case of electric locomotives, diesel-electric locomotives, streetcars, and trolleybuses, and forward and reverse in the case of machine tools and machines. The shaft in an electric reverser, to which are connected electric contacts, is usually equipped with an electropneumatic, pneumatic, or electromagnetic drive.
N. A. ROTANOV