| 摘要 |
A thyristor type control circuit for an electric traction motor for a road vehicle includes a thyristor chopper circuit controlling the average current through the armature and series field winding of the motor. The control circuit includes various switch arrangements for switching the armature connections for forward motoring, reverse motoring and electrical braking, but there is a current threshold detector circuit which prevents operation of these switch arrangements when the armature current exceeds a predetermined value. When braking is initiated, therefore, the current flowing is low and since the field winding is in series braking effort cannot build up. The invention provides a contact which connects the field winding to a d.c. supply while the armature current is below the threshold level during braking. |
