GB776341A - Improvements in or relating to electrical testing equipment - Google Patents

Abstract

776,341. Electric tests. BRYCE ELECTRIC CONSTRUCTION CO., Ltd., and BREWER, S. R. B. July 8, 1954 [July 20, 1953], No. 20036/53. Class 37. Apparatus for measuring the power factor of an inductive load comprises a capacitor or resistor arranged in series with a tapped coil operatively associated with a current-transformer and ammeter adapted to be connected to the load whose power factor is to be measured, whereby the ammeter is adapted to give a measurement of the vectorial sum of the line current and the capacitor or resistor current multiplied by the number of turns of the coil. In Fig. 1 a tapped coil 1 placed over the jaws of a clip-on ammeter 10 may by switch 3 be seriesconnected with a capacitor 2 across inductive load 8 under test. Firstly, the line current Il, Fig. 2, of load 8 is measured by ammeter 10 in the normal way and then switch 3 is closed and the coil turns 1 adjusted until ammeter 10 gives a minimum reading and thus Iw; the power factor of the load 8 is then Iw/Il. In Fig. 2, E represents the supply voltage and Ic the capacitor current multiplied by the number of turns of the coil 1. The latter may comprise 1000 turns arranged with rotary switches so that any number of turns between 10 and 1000 can be selected. A current transformer with or without a split core may be used instead of a clip-on ammeter. If the supply to the load is multiphase the capacitor or resistor must be in the same phase as that in which the load current is to be measured.