| 摘要 |
PROBLEM TO BE SOLVED: To freely control output of an inverter by an inexpensive means by providing an operation stop time during operation of the inverter and changing the ratio between the operation time and the stop time so as to control the output. SOLUTION: When a signal (S) showing a voltage set value, a power set value, etc., in relation to an inverter set according to conditions of an induction. furnace is input in a comparative function 11, the function 11 compares it with the lowest level value which is recorded beforehand and can be output by the inverter. When it is lower than the lowest level output which can be output by the signal (S), the function 11 inputs the deviation value as a deviation signal in a stop signal preparation function 12. The function 12 records an operation stop time for an operation time beforehand corresponding to the deviation signal value and after operating it for a prescribed time according to the input deviation signal value, the stop signal is output for a prescribed time. While gate signal preparation functions 13U, 13V, 13W input the stop signal from the function 12, they stop outputs of the gate signals. Power supply to an induction furnace can be thus reduced. |
