| 摘要 |
PROBLEM TO BE SOLVED: To reduce the size of a high resistance unit, by a method wherein the high resistance unit which is made of synthetic resin and conductive particles and makes a time constant a required value with a circuit capacitance is con nected between at least one conductor on the load side of a switch and a con tainer. SOLUTION: A high resistance unit 25 is connected between each branch bus-bar and the earth. The high resistance unit 25 is made of the mixture of synthetic resin and conductive particles with a required composition corresponding to the resistance value of the resistance unit 25 and formed into a cylindrical shape. Polyamide resin, epoxy resin, etc., can be employed as the synthetic resin. Fine particles of carbon, graphite, metal, conductive polymer, etc., can be employed as the conductive particles. A residual DC voltage is discharged with a time constant τ=CR which is determined by the resistance value R of the high resistance unit and a circuit capacitance C. By adjusting the content of the carbon particles, a higher resistance value than the value of a high resistance unit made of ceramic can be obtained. |
