| 摘要 |
<p>1353040 Detecting thermal overloads in electric machines UNELEC 1 Oct 1971 [2 Oct 1970] 45922/71 Headings H2A and H2K [Also in Divisions H3 and G4] A rotary device, such as a rotatable electrical machine, e.g. electric motor, incorporates a thermal overload detector which comprises a magnetic member 5 carried on a rotatable part of the device and whose magnetic permeability varies with temperature and whose Curie temperature equals the overload temperature to be detected, a stationary magnetic bridge 6 which incorporates two polepieces 10, 11 separated by an air gap 12, and a magnetic field detector 13 disposed in the air gap, the member and bridge being so arranged that during each rotational cycle of the rotatable part the member 5 consecutively passes one polepiece 10, the air gap 12, and the other polepiece 11. The member 5 may be carried by a coil head of a wire-wound rotor, a synchronous motor inductor, a D.C. motor commutator segment or, as shown, the short-circuiting ring 4 of a squirrel cage winding. The polepieces may be electromagnetic or permanently magnetic, and the detector may be a Hall effect device or a magneto resistor, for actuating an alarm or a motor supply circuit breaker.</p> |
