| 摘要 |
<p>865,649. Protective cut-out systems; control of motors. WESTINGHOUSE ELECTRIC CORPORATION. Jan. 16, 1959 [Jan. 20, 1958], No. 1651/59. Classes 38 (3) and 38 (5). [Also in Group XXXV] A protective system for a motor comprises at least one temperature-sensitive resistance element 24 having a positive temperature coefficient of resistance and embedded in or attached to a current carrying winding 30 of the motor, a relay 45 having a coil 46 in series with the element 24 and a low voltage source, and a contactor 34 having an operating coil 36 in series with a voltage supply and the contacts 44 of the relay 45. Under normal conditions the coil 46 of the relay 45 is energized and the contacts 44 are closed, but under overload conditions the rise in temperature of the motor winding causes a sudden increase in the resistance of the element 24 and the relay 45 opens to de-energize the contactor coil 36. A threephase motor may have an element 24 associated with each phase winding. Fig. 3 (not shown) illustrates a modified circuit in which a starting relay provides for automatic resetting when the temperature of the motor returns to normal.</p> |
