Page 341 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

xviii Nett weight of the circuit breaker with oil in kg ......
xix Overall dimensions of OCB mounted on frame ......
xx Ambient temperature for which OCB is designed ......
xxi Auxiliary voltage for shunt trip coils ......
xxii Auxiliary voltage for under-voltage release ......
xxiii Auxiliary supply voltage for motor drive ......
14 Check the stationary, fixed, arcing, intermediate and main contacts. Clean them with a steel wire brush or
sandpaper grade ‘0’ to remove any deposit due to oxidation. Figs 1 and 2 are given for your guidance.

Note: If pittings are heavy, use a flat file to remove the pittings. If the surface area is reduced more
than ten percent due to pittings it will be better to replace the contact points.

15 Clean the contact by using CTC solution.
16 Check the internal control wiring along with the given wiring diagram of the manual.
17 Use a continuity tester to test the continuity of each wire from point to point.

Note: If the internal wiring cables are damaged replace them. Check for loose terminations and
tighten them.

18 Measure the trip coil resistance and compare with the earlier measurement.
Note: There should not be any change in coil resistance.

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CITS : Power - Electrician & Wireman - Exercise 116