GB371855A - Improvements in or relating to apparatus for testing high power electrical equipment - Google Patents

Abstract

371,855. Dynamo-electric machines. SIEMENS-SCHUCKERTWERKE AKT.- GES., Siemensstadt, Berlin. Jan. 21, 1931, No. 2051. Convention date, April 15, 1930. [Class 35.] Exciting.-An apparatus for testing high power electrical equipment comprises a generator arranged to be short-circuited and to subject the equipment under test to the short-circuit current, and means are provided to supplement the generator excitation and so counteract any field weakening resulting from the short-circuit current. Rapid fading away of the short-circuit current is therefore prevented. Fig. 1 shows a generator 2 which can be short-circuited by an oil switch 4 undergoing test. A resistance 8 in the circuit of the separately excited field winding 3 is adapted to be shunted by a switch 9 when the switch 4 is closed. In Fig. 2, a weakly saturated transformer is arranged with its windings 10, 11 in series with the armature 5 and shunt field 6 of the exciter whereby an additional electromotive force is generated in the exciting circuit 3 when the switch 4 is closed. In a further modification, an additional series exciter in the exciting circuit has its field winding normally shunted by a switch which is opened when the testing generator is short-circuited. Alternatively, the main exciter 5, Fig. 4, may have an additional series winding 15 normally shunted by a switch 12 which is opened when the test is commenced. With this arrangement, the short circuit current drops somewhat from the maximum, and to avoid this, the test may be carried out in a reverse manner. A switch 16 in the main exciting circuit 3 is kept open while the field 6 of the exciter 5 is energized. The switch 4 is closed and the test is started by closing the switch 16, the switch 12 being opened, and the short-circuit current increases from zero to a maximum, at which the switch 4 may be opened. A flywheel may be provided on the shaft of the exciter. The exciting current during short-circuit should be about five times that required at no load.