GB230575A - Improvements in starting apparatus for electric motors - Google Patents

Abstract

230,575. Gowan, S., and Metropolitan- Vickers Electrical Co., Ltd. Dec. 29, 1923. Master control systems.-Sections of a starting resistance 4 of a series motor 1 are successively shorted by contactors 66, 67, 68 operated by coils 69, 70, 71 sensitive to a rise of voltage across the terminals of the motor, means being provided to prevent the failure of the successive action should the voltage across the supply mains 5. 6 fall below the normal. Under normal conditions, closure of a switch 60 causes the energization of a coil 61 to close a contactor 62 thereby starting the motor 1. When the voltage across the motor terminals rises sufficiently the coil 69 closes the contactor 66 and also a switch 72. which connects the coil 70 across the terminals so that is closes the contactor 67 and also a switch 75 upon a further rise of voltage. The coil 71 eventually closes the contactor 68. If the voltage across the mains 5. 6 is below its normal value, the voltage across the terminals of the motor may not reach a value sufficient to cause the closure of the contactor 66 or the succeeding ones 67, 68. In such an event a switch 81 operates upon sufficient diminution of the motor current to short a resistance 78 in series with the coils 69, 70, 71, thereby increasing the effective voltage across them so that the contactors act in a normal manner. The switch 81 acts quicker than the contactors 66, 67, 68 thereby preventing rapid cutting out of the resistance. In a modification the switch 60 is replaced by a drum controller giving both forward and reverse drives and also a starting position in which the motor runs continuously with full series resistance. In a further modification series resist. ances are substituted for the switches 72, 75.