Methods of measuring arc-drop voltage on mercury-arc rectifiers

THE over-all efficiency of a mercury-arc rectifier unit is determined by the segregated loss method. The losses in the component parts of the unit — the rectifier transformer, rectifier, and its auxiliaries — are measured separately, and the efficiency is calculated. The methods used for measuring the losses are specified in the American Standards Association (ASA) Standard for Pool Cathode Mercury-Arc Power Converters.1 This method is used for determining the efficiency, instead of measuring the power input and output of the unit, for two reasons: 1. The losses constitute a relatively small percentage of the unit rating (approximately 5 per cent for a d-c output voltage of 600 volts) and can be determined more accurately by individual loss measiuements. 2. To set up a complete rectifier unit in the factory for a full-load test would be costly and is not always pcactical, because of the limitations of available testing facilities.