Other Test of Circuit Breakers

1. Temperature Rise Test
2. Mechanical Test

1. Temperature Rise Test

For measuring temperature to find temperature rise either thermocouples, self resistance method or thermometer is used:
In the above circuit thermocouple is used :

• In the test circuit a special transformer is used.
• This transformer has primary 230 V to 440 Volts rating when secondary voltage is of 5 to 15 volts.
• The test voltage is adjusted by regulator.
• By regulating the voltage a required continuous high current is sent to the test terminals.
• The high current is measured by C.T. Current produces heating effect and temperature increases . Temperature (T) is measured by thermocouple or thermometer.
• Ambient temperature is known (T_a).

∴ Temperature rise = T – T_a is found.

• The rated voltage with rated frequency is applied in the circuit.
• A continuous current is passed till steady temperature is reached. The readings of temperature of various conducting, insulating and structure parts are taken every after 1/2 Hr or 1Hr.
• The maximum temperature of the parts shall be within the prescribed limits.
• The thermocouple comprises a junction of two dissimilar materials.
• The emf induced depends upon temperature difference between the hot junction and the cold end.
• The hot junctions on fixed on the parts of isolator (contacts of isolators, terminals insulators etc.)
• The output of thermocouple is measured by potentiometer or digital voltmeter.
• The temperature is calculated for the calibrated value (°C per Milivolts)

2. Mechanical Test

• This is for testing reliability of mechanical operation of isolator.
• The isolator contacts are opened and closed several times.
• The contacts are closed and opened by usual way (manual or motorized) After this test, all contacts, linkages, are thoroughly checked.
• The dimensions of all these should be in original limits.
• If any part has failed mechanically, the dimensions are out of permissible limits.
• Generally 1000 close-open cycles are specified in standards.