1493578 Control of DC motors DOUBLEFELL Ltd [trading as INTEGRATED CIRCUIT CONTROLS] 2 Dec 1974 [1 Dec 1973] 55774/73 Heading H2J [Also in Division G3] The drum of a washing machine is driven by a D.C. motor 68 having a series field winding 66 connected to a bridge of triacs 63 and diodes 64, 65 controlling the armature 68, the triacs being controlled by firing pulses from transistor amplifiers 60, 61 which transmit firing pulses supplied on lines 57, 58. These pulses are generated by a circuit including a pair of monostable multivibrators and logic gates, Fig. 5 (not shown), this circuit determining the direction of rotation and period of energization of the motor whereby it is cycled to run in one direction for a predetermined time, come to rest in a predetermined time, repeat this sequence in the opposite direction and so on. One or other triac 63 is fired to produce one or other direction of rotation, whereby the armature 68 receives the half-wave rectified A.C. of one polarity at all times and the field winding 66 receives half-wave rectified A.C. of one or other polarity, which arrangement is stated to reduce armature sparking.
