. Electric railway journal . n the control repairmen of the ElevatedRailroads are equipped with a voltage-control rheostatwith resistance sufficient to reduce the line voltages to300 or 350, for use between substations or at the endof a line where failures occur most frequently. Byreproducing low-voltage conditions a repairman is ableto determine whether the failure was due to this cause. The rheostat is shown at the right in the cut in thenext column. It is a perforated steel box with handles,in which a set of ordinary car heater coils is a slate base fastened to the side of the bo
. Electric railway journal . n the control repairmen of the ElevatedRailroads are equipped with a voltage-control rheostatwith resistance sufficient to reduce the line voltages to300 or 350, for use between substations or at the endof a line where failures occur most frequently. Byreproducing low-voltage conditions a repairman is ableto determine whether the failure was due to this cause. The rheostat is shown at the right in the cut in thenext column. It is a perforated steel box with handles,in which a set of ordinary car heater coils is a slate base fastened to the side of the box is arheostat arm with contact points so tapped into theheater-coil circuits as to give a range of voltage from250 to 450 in 25-volt steps. To conduct a test thisoutfit is arranged with one end of the heater circuitconnected through a switch and fuse to the trolley, andthe other end is grounded on the track rail. A thirdwire leading from the rheostat arm is then connectedto the main switch in the car. All of the heaters and. 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
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