×

Control system for an AC elevator

  • US 4,741,415 A
  • Filed: 12/22/1986
  • Issued: 05/03/1988
  • Est. Priority Date: 12/20/1985
  • Status: Expired due to Fees
First Claim
Patent Images

1. A control system for an elevator driven by a three-phase induction motor (5), comprising:

  • (a) an upward driving thyristor circuit including first and second reversed polarity thyristor pairs (20a, 21a;

    24a, 25a) individually connected between first and second phase terminals (R, S) of a three-phase AC power source and said motor;

    (b) a downward driving thyristor circuit including third and fourth reversed polarity thyristor pairs (22b, 23b, 26b, 27b) individually connected between said first and said second phase terminals of said power source and said motor, said downward driving thyristor circuit pairs being disposed in parallel with respective upward driving thyristor circuit pairs;

    (c) a three-phase/single-phase switching thyristor circuit connected between a third phase terminal (T) of said power source and said motor, and including a fifth pair of reversed polarity thyristors (28c, 29c); and

    (d) firing circuit means (18) for selectively and sequentially controlling the conduction of all of said thyristors in a predetermined pattern and based on a difference signal between actual and commanded speed signals in such a manner as to substantially equalize the overall duty cycles of the individual thyristors for all operational modes,(e) wherein, when said motor is subjected to DC damping, the conduction of a thyristor selected in said upward driving thyristor circuit and the conduction of a thyristor selected in said downward driving thyristor circuit is controlled, and wherein said thyristors (25a, 26b) selected during DC damping in an upward direction are different from said thyristors (21a, 22b) selected during DC damping in a downward direction.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×