GENERATOR: Molded case circuit breaker

Friday, December 21, 2007

Molded case circuit breaker

Both MCB and MCCB have thermal and electromagnetic part. But, MCCB is used to handle the high current. The MCCB’s handle three positions.

Some MCCB has thermal current (rated current) setting knob. We can adjust the rated current. 3 – pole or 4 – pole MCCB are available.

There are 3 effects to trip the MCCB

1). Thermal

2). Magnetic

3). Auxiliary tripping

1 Shunt trip

1 U.V.T trip

We can control the rated current (Ir) by using rated current adjust knob and also have Im adjuster to handle the short circuit current. Also we can adjust the delay time to trip the MCCB.

Shunt coil and UVT (Under Voltage Tripping) coil of the MCCB)

How to connect the shunt coil or UVT coil to the MCCB

First trip the MCCB by using manual test button and after connect the UVT or shunt coil to the MCCB.

v Shunt coil

Shunt coil is normally open contact point. When energized the coil the MCCB will be trip.

UVT coil (Under Voltage Trip)

UVT coil is normally close point. When de-energized the coil MCCB will be trip. UVT coil is used to detect the phase.

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