GB849177A - Electric motor control apparatus - Google Patents

Abstract

849,177. Control of A.C. motors. STUBNITZ GREENE CORPORATION. Dec. 3. 1958 [Dec.12, 1957], No. 38972/58. Class 38 (3). [Also in Group XXXV] An electric motor control system comprising a split phase induction motor has a temperature-sensitive element embedded in the motor windings such that should the motor temperature rise above a predetermined value the supply thereto is removed. A split phase motor 2 driving a refrigerator pump has a sealed bimetal switch 23 embedded in the motor windings 12, 13, the circuit including a composite bimetallic switch 26. At starting a circuit is established from supply terminal 31, bimetal 34, contacts 35, 37, contacts 40, 44, heater 42, bimetal 46 and thence simultaneously firstly by way of conductor 48, main running winding 12 to supply terminal 32 and secondly, link 50, contacts 49, 51, arm 52, starting winding 13 to supply terminal 32. Thus both running and starting windings are energized. After a time sufficient to enable the motor to start the starting current through the bimetal 34 will cause it to deflect sufficiently to open contacts 49, 51 to de-energize the starting winding 13 whereafter the motor will run normally. If the motor becomes overloaded a greater current will flow in the bimetal 34 causing it to deflect further, thereby engaging peg 58 to open contacts 40, 44 to remove the short-circuit on the bimetal 38. Bimetal 38 will now carry current and the combined effects of this current and heater 42 cause the bimetal 38 to deflect sufficiently to open contacts 35, 37, thereby deenergizing the motor 2. In the event that the motor 2 becomes overheated the contacts of the bimetal switch 23 close, whereby the additional heater 53 becomes energized. This heater is sufficient in itself to cause the bimetal 38 to deflect and open contacts 35, 37 to remove the supply from the motor. The peg 58 is provided to ensure that contacts 40, 44 remake before contacts 49, 51.