| 摘要 |
Case 3009 IMPROVED APPARATUS FOR OVERLOAD PROTECTION Apparatus for permitting limited operation in the overload region of an electric motor by controlling motor load when operating in that region. A sensor senses the current supplied to drive the motor, or senses the electrical energy supplied to the motor, or senses some other load related parameter, and provides a signal representing motor load to-an accumulated thermal overload circuit which provides an output signal representing the accumulated value of any motor thermal overload. An overload capacity circuit has set into it the maximum thermal overload capacity the motor can withstand and it provides an overload capacity signal representing this. A desired thermal reserve circuit has set into it a value representing the thermal reserve and it provides a thermal reserve signal representing this. A summing means receives the overload capacity signal, the accumulated thermal overload signal, and the desired thermal reserve signal, and provides a net signal representing the amount by which the desired thermal reserve signal plus the output signal exceed the overload capacity signal. This net signal is used to reduce the motor load in proportion to the value of the net signal. |
