Brushless motor including forced commutation responsive to rotor movement

Claim 1

A brushless synchronous motor drive arrangement comprising in combination: a. an inverter bridge including positive and negative DC busses defining positive and negative DC sides of said inverter bridge; b. at least first and second inverter electric valve pairs (11, 14; 12, 15) connected to said busses, the valves of said valve pairs including gate control means and also including corresponding output leads for connection to corresponding armature coils (U, V, W) for rotating a motor rotor, said leads defining the AC side of said inverter bridge; c. detection means (33) for detecting the rotary position of said rotor, a control circuit (34) operatively connected to said detection means, said control circuit (34) controlling and being connected to said gate control means of said inverter electric valve pairs; d. a forced commutation circuit including a switching circuit (37) operatively connected to and responsive to said control circuit and including DC supply means (36) said switching means (37) and DC supply means (36) being so connected across said positive and negative busses as to supply DC electricity in a direction counter to the flow of electricity in said positive and negative busses in commutation as determined by said control circuit (34); e. a bypass circuit including a diode bridge having diode pairs 21, 24; 22, 25) corresponding to said inverter valve pairs, said diode pairs including bypass leads connected to corresponding armature coils as well as to said inverter electric valve pairs on the AC side of said inverter bridge, said diode pairs and said inverter electric valve pairs being thus both connected to said armature coils, however, in opposite polarity; and, f. at least one bridge control electric valve pair (17, 18) connected between said positive and negative DC sides of said inverter bridge and said diode bridge, said bridge control electric valve pair being connected in the same polarity as said diodes, whereby, at the time of commutation on the positive side of the inverter bridge, electricity is allowed to pass through only those diodes of the bypass circuit which correspond to the inverter electric valves disposed on the negative side, and at the time of commutation on the negative side of the inverter bridge, electricity is allowed to pass only through those diodes of the bypass circuit which correspond to the inverter electric valves disposed on the positive side of the main inverter bridge so that the electromagnetic energy stored in the armature winding can be eliminated.