Patent GB-671560-A (GB)
Title: Improvements in or relating to electric motor control systems
IPC: B66B1/08
Filed: 1950-01-23
Abstract: 671,560. Control of D.C. motors. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. Jan. 23, 1950. [Feb. 11, 1949] No. 1699/50. Class 38 (iii). [Also in Group XXXV] An electric motor control system comprises a motor, a main generator for supplying electrical energy to said motor, the armatures of said motor and said main generator being connected in a loop circuit, a regulator generator for supplying field energization to said main generator, said regulating generator having a first field winding connected in series with a resistor across said loop circuit for energizing said first field winding in accordance with the motor armature voltage, and capacitor means adapted to be connected in parallel with said resistor whereby the rate of change of energisation of the regulator generator first field winding can be controlled in accordance with the time constant of the circuit constituted by said resistor and said capacitor means. The Ward- Leonard lift control system, comprising a motor M and generator G, described in Specification 480,761 is modified by the inclusion of an auxiliary inductor relay AE which co-operates with up inductor plate AUE and down inductor plate ADE and provides an additional slow-down point for the car. The system of Fig. 1 also differs from the prior system referred to by the provision of capacitors C1, C2, C3, which are connectible in shunt with resistor r6 and in series with differential field winding Rf of regulator R so as to provide a smooth deceleration of the car from running speed to landing speed. The main switch MS controls forward and reverse contactors U, D, and a relay X which energizes inductor relays E, AE, F. Speed relays V, AV, are controlled by the forward and reverse contactors and the inductor relays so that, when starting, contacts V1, AV2, close to remove resistors Ar, AVr, and increase the energization of the generator pattern field winding Gf. At the same time contacts V3, AV1, close to connect capacitors C3, C2, across resistor r6, the capacitor C1 having been connected across the resistor upon closure of the forward or reverse contactor The capacitors C1, C2, C3, provide a substantial degree of damping during full speed operation. When stopping, inductor relay E opens contacts E1, E2, to de-energize the relay V, so introducing resistor Ar and removing capacitor C3. The inductor relay AE then opens contacts AE1, AE2, to de-energize relay AV, introduce resistor AVr, and remove capacitor C2. The car is finally stopped by operation of inductor relay F. The contacts V3 may be replaced by a permanent connection, or the capacitor C3 may be omitted. A capacitor may be connected across the resistor r6 only during the deceleration period, Fig. 4 (not shown), an auxiliary resistor of high ohmic value ensuring the discharge of the capacitor after the car has come to rest. The bridge circuit within the rectangle 35 of Fig. 1 may be replaced by the arrangement shown in Fig. 5. The regulator armature Ra is connected in series with generator pattern field winding Gf and an additional regulator field winding RD through contacts X2 of relay X. The regulator field winding Rd is energized through contacts U2, U3, D2, D3, of the reversing contactors, the resistors Ar, AVr, being controlled as described previously.