| 摘要 |
PROBLEM TO BE SOLVED: To convert the frequency of AC voltage supplied from a commercial AC power source into a frequency of maximal job efficiency, in a switchboard. SOLUTION: A power supply line 10, which begins from an input terminal 8 to which commercial AC voltage is inputted, passes through a turning into DC circuit 11 and relay circuits 13, 14 composed of static relays in this order, and reaches an output terminal 9 to the outside, is provided. Also, a central processing unit 15, which is connected through an analog-to-digital converter 19 to a current reference line 18, which begins from a current detector 12 for detecting a current value on this power supply line, outputs opening/closing control signals to the relay circuits 13, 14 and causes relay circuits to output a rectangular wave, is provided. By using this central processing unit, cycle for opening and closing of the relay circuits is adjusted, and the frequency of the rectangular wave is controlled. |
