. Electric railway journal . CHICAGO ELEVATED—SPRING BALANCE IN CONTACTOR TEST the compressor may not be in operation at the time thetest is made, since the rheostat is of insufficient capacityto operate them. After the testing outfit has been con-nected in this manner, the circuit breaker is tripped andreset on low voltage, the reverses are thrown and thecar control is run up on one-half line voltage. If the control repairman is unable to locate defectsby varying the voltage on the contactors, the pressure is reduced to 350 volts and the control is notched up toa position in which the maximum
. Electric railway journal . CHICAGO ELEVATED—SPRING BALANCE IN CONTACTOR TEST the compressor may not be in operation at the time thetest is made, since the rheostat is of insufficient capacityto operate them. After the testing outfit has been con-nected in this manner, the circuit breaker is tripped andreset on low voltage, the reverses are thrown and thecar control is run up on one-half line voltage. If the control repairman is unable to locate defectsby varying the voltage on the contactors, the pressure is reduced to 350 volts and the control is notched up toa position in which the maximum number of contactorsis in service. An ordinary spring balance is employedto test the contactor pull if necessary. Very obsti-nate cases of trouble have been discovered in this making the test the hook end of the spring balance. CHICAGO ELEVATED—CONTROL AND JUMPER TEST SETS is fastened to the contactor switch mechanism. Inthis position the repairman reads the force required topull out the contactor plunger. If the contactor coilsare not short-circuited, a condition which the rheostattests should show, the contactor, as a rule, will pullout at about 75 lb., providing the brass bushing andair-gap washer in the contactor are not unduly test indicates contactors which have worn air-gapwashers or bushings. Contactors requiring a forceof 100 lb. or more to pull them out are quite certain tocause trouble in service. Cases have been found wherethe air-gap washers were worn through and a was required to move the contactor plunger. Pneumatic control is also tested with the voltage-varying rheostat. If any particular magnet fails tooperate in this test, the inspector resorts to his valvegage as a means of checking or adjusting the gage is shown on page 553. In making this checkadjus
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