| 摘要 |
PURPOSE:To ensure protection against overload for a DC motor by a method wherein an overload signal is yielded when the overload current squared mean value in a prescribed period of time exceeds the rated level. CONSTITUTION:A current is detected by a current detector 3 and is transmitted through a filter circuit 4 and a clock circuit 5 from which a current Ij is yielded for every DELTAt hour. The current Ij is squared in a multiplier 6, producing an Ij<2>. This quantity and the difference thereof from the square of the DC generator 1 rated current IN that is (IN<2>-Ij<2>), are sequentially stored in a memory circuit 9. The quantities in the memory circuit 9 are then summed up in an adder 10. The memory circuit 9 is so constructed that it memorizes the latest (n) quantity of data. A decision circuit 11 outputs an overload signal into a control circuit 12 upon receiving a positive value from the adder 10. This setup provides protection against overload for a DC motor. |
