Checking cut-out

Checking cut-out

1 Closing voltage

This test should be carried out at a temperature of 25°±10°C and the regulator should be connected to a generator test bed as shown in FIG 11:7. The unit should be operated under no load conditions for between 15 - 18 minutes with the cover installed and with a voltage of between 16.5 volts for an initial operating temperature of 15-20°C or 15 volts for an initial operating temperature of 20-35°C. This will enable thermal stabilization of the unit to be obtained so that the temperature of both the cut-out shunt windings and the bymetallic springs increase due to the heat developed by the windings and reaches the normal operating setting.

Once thermal stabilization has been obtained the generator should be restarted and the speed gradually increased so that immediately the test lamp starts to glow the voltmeter reading may be taken. This will be the value of the cut-out contact closing voltage.

2 Reverse current

This check should be carried out at a temperature range of between 25°±10°C and it is recommended that it is performed as soon as possible after the closing voltage test so that the thermal stabilization remains unaltered. Connect the regulator as shown in FIG 11:8 and gradually speed up the generator to 4500 rev/min for approximately 5 minutes. Ensure that the voltmeter reads at least 14.5 volts and then gradually reduce the generator speed carefully watching the movement of the ammeter needle which should at first indicate a charging current and then gradually move to zero and then to the other side of the scale to indicate reverse current value. If the generator speed is reduced further the reverse current reading will increase to a given value and then suddenly fall to zero which will indicate that the cut-out contact has opened. This limit indicates the maximum reverse current value which should not, under any circumstances, exceed 16 amps.

During this test, to obtain the maximum reverse current possible the reduction in generator speed must not take more than 10 seconds otherwise the battery voltage will drop excessively.