GB642895A - Improved apparatus for the control of energy supplied to an electrical translating device - Google Patents

Abstract

642,895. Automatic control systems for D.C. motors. IGRANIC ELECTRIC CO., Ltd. Oct. 18, 1946, No. 31049. Convention date, Oct. 20, 1945. [Class 38 (iv)] In a speed control system for D.C. motor 10 in which a resistance 13a in series with the armature 10a is varied by a motor 14, the direction of rotation of the motor 14 is determined according to which of its two fields 14c, 14b is energized through a valve and relay selector system operated by a D.C. voltage produced by the difference between a reference voltage at resistor 33 and the output of a tachometer generator 11, driven by the motor. Hunting is prevented by a relay producing adjustment of the reference voltage to allow for the mechanical inertia of the motor 14. General operation.-As shown, upon closure of the start button 18 relays 12 and 17 operate and the motor rotates at the lowest speed, resistor 13a being fully in circuit with armature 10a. Grid 28c is positive relative to cathode 28a, the voltage of tachometer 11 is low and valve 28 conducts, thereby causing valve 38 to cut-off, valve 42 to conduct and relay 21 and 23a to operate. The forward field 14b is energized by relay 16 and the contact arm 13c is moved to reduce the amount of the resistor 13a in series with armature l0a and motor 10 accelerates until the rising tachometer voltage at grid 28c causes a reduction in the energization of relay 21 wherein field 14b is de-energized and motor 14 stops. Similarly, a reduction in the datum voltage, by an adjustment of tapping 33a while the machine is running will cause valve 48 to operate relays 15, 20, 22 and energize field 14c to reverse motor 14. Anti-hunting system.-To prevent hunting, due to the overshooting of the correct position of the contact 13c due to mechanical inertia, the contacts 23c are opened by relay 23 to reduce the value of the tachometer voltage, and therefore the motor speed, at which the - de-energization of the field 14b occurs. The motor 14 is therefore de-excited before the correct setting of 13c is reached and the system inertia carries it forward to the correct position. Similarly, when the tapping 33a is adjusted to a lower speed, hunting is prevented by opening of contact 22c. To effect a difference in the response rates of relays 20, 21 during energization and de-energization, the resistors 43, 49 are in parallel with the diodes 44, 50 respectively. Specification 637,012 is referred to.