GB1132087A - Electrical machines - Google Patents

Abstract

1,132,087. Automatic speed control. SIEMENS-SCHUCKERTWERKE, A. G. Nov. 8, 1965 [Nov.10, 1964], No.47323/65. Heading G3R. [Also in Division H2] In an electrical machine having an electronic commutator arrangement the conduction of semiconductor devices connected to an n phase star winding 1, 2, 3 are controlled by a bridge circuit having branches formed by a resistor RO and a magneto-resistive element A, B, C so that in one revolution of the rotor, the winding will pass n overlapping pulses of current causing the resultant flux vector to transverse 360 degrees in 2n steps. In the D. C. motor shown having a permanent magnet rotor 4 the magneto-resistive elements A, B, C are secured to the stator by an adhesive so as to control the conduction of transistors I, II and III and cause the rotor to step successively through angles of 120 degrees. Part of one end of the rotor is removed Fig. 2 (not shown) so as to ensure that the magneto-resistive elements responds only to one pole of the rotor field. The other end is similarly shaped or drilled with holes to balance centrifugal forces. The power supply is provided from two sources U, U v or alternatively, a single source, a rectified transformer output, or a rectified transformer output driven by an inverter may be used Figs. 6, 7 and 8 (not shown)., Speed control. The speed of the motor may be varied by adjusting the supplies provided that the ratio U: Uv is maintained constant. A circuit for maintaining the speed constant is described Fig. 9 (not shown), in which the voltage induced in one of the stator field windings 2 is passed via a transformer (17) and rectifier (19) to a bridge circuit (16) for comparison with a Zener diode (Z) voltage. The bridge circuit controls the conduction of a transistor (15) connected between the motor and the supply. A resistor (R1) in an arm of the bridge provides speed variation. The supply for this arrangement may be a transformer driven inverter, Fig. 10 (not shown).