Ø QUE-ANS: 10-30 words
[1] What is the primary function of a circuit breaker?
The primary function of a circuit breaker is to isolate any fault that may occur in an electrical system.
[2] What are the principal factors to be considered when selecting a circuit breaker?
The principal factors considered when selecting a circuit breaker are; system voltage, rated load current, the fault value at the point of installation.
[3] What would happen if the circuit breaker was rated at less than the expected fault level?
If the circuit breaker were rated at less than the expected fault level, the breaker would be liable to explode and cause fire.
[4] What is the purpose of a circuit breaker?
The purpose of a circuit breaker is to interrupt fault current as quickly as possible and so keep damage to other pieces of equipment to a minimum.
[5] What duties are springs used for in circuit breakers?
The duties of the springs in a circuit breaker are to open the contacts in the tripping operation.
[6] What current rating range is used with MCCBs?
The current rating used with MCCB’s is 30 – 1500A
The current rating used with MCB’s is 5 – 100A
The current rating used with generator breaker or other large breakers is 600 – 6000A
[7] What maintenance can be carried out on a MCB?
The maintenance carried out on MCB’s is none, as no maintenance is possible on them.
[8] Name the Trips found on a Generator Circuit Breaker.
Under Voltage
Reverse Power
Ø 30-60 words
[1] What is the Function of a Circuit Breaker?
The Circuit Breaker is an Isolating Switch that also acts as a Fuse. It has two designed ratings; one of normal safe working current, and the other against overload, which may also have a time delay.
[2] What factors determine the current rating of a circuit breaker?
The factors that determine the current rating of a breaker are; the maximum continuous permissible operating temperature of the circuit breaker copper work and contacts, the ambient temperature, the temperature rise of copperwork due to the load current.
[3] State why a breaker may not open upon severe and prolonged voltage dip.
Most breakers uses magnetic contact spring forces tends to open sufficient voltage to magnetize are for long time, contact overheated, melts and welded together, thus it cannot be opened after a prolonged voltage dip.