GB1240979A - Reluctance motor power circuit - Google Patents

Abstract

1,240,979. Control of A.C. motors; electric motors. FORD MOTOR CO. Ltd. (Ford Motor Co.). 26 March, 1970, No. 14975/70. Headings H2A and H2J. Each phase of a variable reluctance motor comprises a toroidal winding 20, 26, 30, surrounding a stator disc 38, 40, 42, having wedgeshaped sections 43 of laminated steel spaced by material having a low permeance. A rotor disc 50-52, 54-56 and 58-60 is positioned on each side of a stator disc and is constructed similarly to the stator disc. The periphery of each rotor disc is wound with a thin layer of low permeance material. The windings 20 and 30 are associated with L-shaped laminated steel stator members 16 and 28 while T-shaped members 22, 24 hold the three windings in place. The motor is coupled to a load such as a vehicle driving-wheel and has position and speed sensors. A controller, which is connected to a battery 90 and to the motor windings is adapted to receive signals representing a desired torque, a forward or reverse function, and a system protection input, Fig. 2 (not shown). The battery may be replaced by a generator driven by an engine or induction motor, or a rectifier may be used. S.C.R. 120 is fired, at low motoring speeds, when laminated sections 61 of rotor discs 50, 52, begin to move into alignment with laminated sections 43 of stator disc 38. Capacitor 122 charges and winding 20 is energized at a rate dependent upon the residual inductance of the battery and associated circuitry. As the current reaches its peak, S.C.R. 128 is fired to provide a freewheeling path for the winding-current, the capacitor completing its charging cycle. Then the S.C.R. 120 switches off and the energy stored in the capacitor 122 is returned to the battery through diode 124 and S.C.R. 128. When the freewheeling current in winding 20 decays to a predetermined value, the current is reinforced by triggering S.C.R. 120. The residual charge on capacitor 122 may be reversed by rectifier 130 and inductor 132 before triggering S.C.R. 120, so providing greater current reinforcement. As the laminated sections approach complete alignment, winding current is removed by omitting the gate pulse for S.C.R. 128 at the end of the reinforcing cycle. Thereupon the capacitor 122 discharges through the battery and winding 20. The freewheeling and reinforcing operations are omitted at higher motor speeds. The diode 124 may be replaced by S.C.R. 126 to increase the speed and power of the motor by building up the charge on capacitor 122 over a period before discharging it through the winding 20. As the laminated sections are moving out of alignment, the motor may be braked by firing S.C.R. 120 to produce reverse torque.