Direction control for DC series machine - uses thyristor switching of armature current and braking resistors

摘要

The principal control for this DC series motor is a thyristor (H) which has a chopping-rate determined by a logic unit (E). The current flow in the armature is switched by four thyristors (T1-T4). These are arranged so that if one pair (T1, T4) is gated on, then current flows in one sense relative to the field winding and conversely with the other pair (T2, T3). Braking resistors (RF1, 2) are connected across the armature in series with diodes. A diode (DR) is connected in opposition to the chopping-thyristor to accept motor current in 'off' periods. This system of switching overcomes the problems of mechanical switching of the armature current and is applicable to traction motors.