GB673496A - - Google Patents

Abstract

673,496. Dynamo electric machines. BRITISH THOMSON-HOUSTON CO., Ltd. May 16, 1950 [May 25, 1949], No. 12204/50. Classes 35 and 38 (ii). Commutation is effected in electric motors and generators without the use of contacts by means of the Hall effect. Flux from a permanent magnet rotor is passed through a conducting plate, which may be of germanium or bismuth and is referred to as a Hall plate, whilst an exciting current is passed laterally through it to produce an E.M.F. between its ends. In its simplest form, Fig. 1, a generator having a permanent magnet rotor 1 and stator windings 3, 4, has the Hall plates 5, 6 extending across the stator pole faces so that the working flux passes through them. The Hall plates have terminals at each of their four edges and the lateral terminals 7, 8 are fed by the stator coils. The effect of the simultaneously-reversing current and flux passing through the plates is to produce a Hall voltage between its ends which are connected at terminals 9, 10 to the D.C. output circuit. In the D.C. motor shown in Fig. 3, Hall plates 17, 18 are energized by current from a source 19 and are cut by flux from horse-shoe magnets 14, 15 revolving on shaft 13. The Hall voltages are connected, through a switch 20R for reversing the rotation of the motor, to the coils of a stationary winding 20 which drives a magnetic rotor 16 also mounted on the shaft 13, the Hall plates effecting commutation. In a modification, the functions of the driving magnet and commutating magnets are performed by a single magnet, the Hallplates being placed in quadrature with the driving coils. In a further modification a series of Hall plates, connected to driving coils, are spaced around a magnetic rotor having one or two magnetic discs so that a smooth torque is produced. The Hall plate voltage may be amplified before feeding the driving coils, if required. This is shown, in Fig. 6, for a servomotor in which the Hall, plates 27 are fed with an A.C. error voltage at 28, the output of the plates controlling the supply to the driving coils 32 from A.C. source 29 by means of valves 31, the magnet 26 and Hall plates 27 acting as a commutating device as before. The supply 29 and error signal appearing at 28 are derived from a common A.C. source and the phase and magnitude of the signal voltage controls the current in coils 32 and thus the motor speed. The device is shown as operating a recorder 33 and indicator 34 for a thermocouple 35 whose voltage is compared with that of a standard cell 37, the balance being maintained by a potentiometer 36 driven by the motor, and the error signal being converted to A.C. at 38 for feeding the winding 28.through amplifier 39.