The Biddle 577500 / 57J Energized Winding Resistance Tester is used for measuring the DC resistance of AC energized windings, thus enabling the determination of winding temperature rise while the windings are operated under actual load conditions. The Biddle 57J is suitable for measuring the winding resistance of transformers, chokes, induction coils, heater coils, generators and all types of motors where there are no brushes in series with the circuit being measured. Measurements are possible on either single phase or three phase, three wire equipment.
The Biddle 577500 / 57J Tester is a modified Wheatstone bridge and is used as such on energized or de-energized samples. The Biddle Tester is completely self-contained and measurements are made by balancing the bridge by means of the measuring dials and the null detector. Resistance readings are taken directly from the Biddle 57J, no calculations or multipliers are necessary.
For measurements on windings of a higher current rating than that of the Biddle 577500 / 57J Energized Winding Resistance Tester, a high current adapter is used to increase the tester rating. The adapter is connected to the tester by means of a single cable and an MS type connector. Details of the ratings are given in the specifications. The Biddle 577500, when used properly, can make measurements to determine actual temperature rise with an accuracy of better than one half degree centigrade.