GB1090376A - Improvements in or relating to rotary frequency changers - Google Patents

Abstract

1,090,376. Pole-changing windings for dynamo-electric machines. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Oct. 19, 1965 [Nov. 20, 1964], No. 47387/64. Heading H2A. In a three-phase, pole-changing winding providing first and second pole-numbers simultaneously, each phase is divided into two sections 17, 18; 19, 20; and 21, 22, respectively, which are connected in a closed circuit carrying D.C. excitation from a source 43 and providing a first pole-number field and having a high impedance to the second pole-mumber. The winding acts as a double-star winding of the second pole-number at terminals 7, 8 and 9. The winding is intended for use in a self-driving frequency-changer similar to that described in Specification 1,050,018, the D.C. excitation serving to prevent frequency droop, due to slip, on load. The winding is of P.A.M. type, and may be on primary or secondary member, or both. A star-point may be obtained by tapping the D.C. source (Fig. 4, not shown) or by a capacitance divider (Fig. 5, not shown). Stator and rotor may each carry primary and secondary windings of different pole-numbers (Figs. 9, 10, not shown) to avoid the use of brushes, D.C. excitation being provided by rectifiers mounted on the rotor.