×

Control logic for a phase controlled rectifier system

  • US 4,152,758 A
  • Filed: 09/26/1977
  • Issued: 05/01/1979
  • Est. Priority Date: 09/26/1977
  • Status: Expired due to Term
First Claim
Patent Images

1. A power control system for an electric motor powered from an alternating voltage source comprising:

  • (a) a phase-controlled rectifier circuit having a-c input terminals adapted to be connected to the alternating voltage source, a pair of d-c output terminals, and means including a plurality of controllable electric valves for interconnecting the input and output terminals, said valves being cyclically fired at firing angles that can be varied to control the average magnitude of d-c voltage across said output terminals;

    (b) a filter circuit including a shunt capacitor connected to said d-c terminals;

    (c) power regulating means for connecting said filter circuit to the motor and operative to control the motor power as desired; and

    (d) control means for periodically supplying firing signals to said rectifier circuit so as to fire said valves at variable firing angles, said control means including;

    (i) first means for generating a train of first firing signals in synchronism with the alternating voltage at said input terminals, said first means including means responsive to the d-c voltage across said capacitor for varying the firing angles of said first firing signals as necessary to maintain substantially a desired magnitude of capacitor voltage;

    (ii) second means responsive both to said capacitor voltage and to the alternating voltage at said input terminals for generating second firing signals every time the instantaneous magnitude of the latter voltage becomes greater than the actual magnitude of capacitor voltage; and

    (iii) means for coupling to said rectifier circuit said first firing signals and additionally any second firing signal that is generated after a first firing signal during each half cycle of alternating voltage.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×