GB1321608A - Synchronous motor systems - Google Patents

Abstract

1321608 Synchronous motors having D.C. excitation; control of AC motors C A PARSONS & CO Ltd 30 June 1970 [14 Aug 1969] 40635/69 Headings H2A and H2J In a synchronous motor system which ineludes a synchronous electric motor having a stationary armature winding 1 ... 3 and a rotor carrying a field winding 6 connected via rectifying means, e.g. a bridge 7 to an armature winding 8 ... 10 of an A.C. exciter having a stationary field winding 11 connectible via a switch 12 to a D.C. supply the exciter armature winding 8 ... 10 and rectifying means 7 being rotatable with the motor field winding 6, and short circuit means, e.g. semi-conductor controllable rectifier devices 13, 14 operable to complete a current path through the motor field winding 6 and bypassing the rectifying means 7, the short circuit means is operated in response to motor speed by a control circuit 25 connected to such means and to the secondary winding 17 ... 19 (rotatable with the motor shaft) of a frequency boosting transformer whose primary winding 20 ... 22 is stationary; the control circuit 25 causes the short circuit means 13, 14 to by-pass the rectifying means 7 until a predetermined speed close to synchronous speed is reached, whereupon the short circuit is removed, excitation is applied to the exciter field winding 11, and excitation current is supplied by the exciter armature to the motor field winding. As shown, a current limiting resistor 15 is connected to the field winding 6 and is shunted by a semi-conductor controllable rectifier 16 controlled by the circuit 25. The switch 12 is closed by a sensing device 26 responding to a signal transmitted through the transformer from the control circuit 25, and the circuit 25 operates this switch 12 and the devices 13, 14, 16 either simultaneously or at very slightly different times. Instead of 3 phase, the system may be either multi- or singlephase.