| 摘要 |
An electrical appliance (1) is protected against overheating by the provision of a plurality of series-connected, auto-reset type thermal cut-outs (2) each located in the appliance in the region of a potential hot-spot, and by the provision of a thermal relay comprising a bistable thermally-responsive switch (3) connected in the main power supply line of the appliance and a heater (4) associated with the switch and connected so as to be energized in the event of any of the cut-outs going open circuit. The thermally-responsive switch (3) will thus operate, due to heat generated by the heater (4) and after a certain time delay, in response to any of the cut-outs (2) operating in response to local overheating. The cut-outs (2) can be located at relatively inaccessible regions of the appliance and do not have to be accessed to be manually reset, and the thermally responsive switch (3) can be located in a readily accessible prominent position. This arrangement overcomes the problem of having to have the appliance attended to by a service engineer whenever a cut-out nuisance trips in response to a transient condition, as is the case conventionally when non-auto-reset type cut-outs are employed. <IMAGE> |
