GB941152A - Improvements in and relating to synchronous motors - Google Patents

Abstract

941,152. Synchronous motors; converting; distributers. LODGE-COTTREL Ltd. Oct. 1, 1962 [Oct. 25, 1961], No. 38140/61. Headings H2A, H2B and H2F. In a synchronous motor-driven rotary rectifying switch the required output polarity is obtained by supplying both the motor and switch from the same A.C. source and making the motor self-synchronizing by supplying D.C. to its rotor from an alternator rotor through a bridge rectifier where both rotors and rectifiers are mounted on the rotating shaft. The motor stator winding 26 is supplied from a 3-phase supply and salient pole rotor 16 is supplied with a D.C. synchronizing supply from rectifier bridge 12 which is supplied with A.C. from winding 27 on rotor 18 of the exciter alternator 13. The rotor 16 also has a squirrelcage starting winding and the alternator may be permanent magnet excited or have a wound stator 17. The device may be used to supply high voltage D.C. to an electrostatic dust precipitator. The switch comprises a rotor disc 24 of insulating material with four discharge points 37-40 spaced around the periphery at 90 degrees from each other, with adjacent pairs being connected together by wires 41, 42. Four stationary collector shoes 43-46 are spaced to clear the discharge points when the disc rotates. The high voltage A.C. supply to the rotary switch is derived through transformer 53 from one phase of the motor supply and is applied to shoes 44, 46 and passes across the respective gaps to shoes 45, 43 and the external circuit: shoe 46 being more negative than shoe 44, say, so that the D.C. polarity is as shown. When the disc has rotated clockwise through 90 degrees, point 40 will now lie under shoe 44, which is now more negative than shoe 46, and shoe 43 will again collect a voltage which is negative with respect to earth so the disc rotating at synchronous speed will act as a rectifier.