| 摘要 |
PURPOSE:To increase reliability of contact so as to simplify the maintenance without juxtaposing contacts and application of gold plating thereto. CONSTITUTION:An arithmetic circuit 13 controls a main circuit units 4, 7 and display 26 according to the intensity of current in a main circuit 3 as well as input signals from operation units 19, 20 on the basis of the control program preliminarily stored, and also controls voltage application means 21, 22 to work when the working time or stop time of an excitation coil 5c having auxiliary contacts 51a, 52a, 51b exceeds a specified time. With such a construction, pulsive voltage is applied from the means 21, 22 to the contacts 51a, 52a, 51b at every specified period so that the oxide film of the contacts 51a, 52a, 51b are broken. |
