| 摘要 |
PURPOSE:To rationally protect depending upon the thermal resistance of an auxiliary motor by allowing the restart if the value resulting from adding the quantity of heat of the motor immediately before starting and the quantity of heat based on a starting current is within the resistance of the motor. CONSTITUTION:The secondary current of an instrument transformer 3 is input through an input signal converter 21 to a square integrator 22. This output signal is applied to addition/subtraction calculator 23, which subtracts the output signal of a setter 24 set in response to the heat discharge amount determined by the type and capacity of the motor, and is input to a comparator 25. The comparator 25 calculates to compare with the output signal of a setter 26 set in response to the thermal allowable resistance determined by the type and the capacity of the motor, and applies the result to an output signal contact output unit 27. Accordingly, if the quantity of heat of the motor exceeds the thermal allowable value of the motor 4, a relay 6 is operated to prevent the motor 4 from restarting. |
