Electrical braking transitioning control

Claim 1

An improved electrical brake blending apparatus for a direct current electric motor power system, the motor having first and second power terminals and including a field winding and an armature, the system including a DC power source connected between a first and second power bus, power contacts for connecting the first terminal of the motor to the first power bus, power regulating means for connecting the second motor terminal to the second power bus, unidirectional conducting means connected between the first terminal of the motor and the second power bus and means for initiating electrical braking of the motor by reversing the relative polarity of the motor field winding and armature and opening the power contacts while the armature is rotating, the improvement comprising: (a) a first relatively low ohmic value resistance; (b) first switching means, said switching means and said resistance being connected in a series circuit path in parallel with the contacts; (c) means for momentarily actuating said first switching means upon initial opening of the contacts whereby an alternate current path between said motor and said power supply is provided in order to establish a desired polarity of flux in the motor to enable electrical braking; (d) a second relatively low ohmic value resistance; (e) a second switching means; (f) means for connecting said second resistance and said second switching means in a series circuit path in parallel with the contacts; (g) means for closing the contacts during electrical braking for converting said system from regenerative to plug braking; and, (h) means for actuating said second switch means immediately prior to closing the contacts to thereby provide an alternate armature current path to enable relatively smooth transitioning from regenerative to plug braking.