Home / Blog / Technology / Selection of low-voltage circuit breakers and common fault handling methods

Selection of low-voltage circuit breakers and common fault handling methods

By:Nader Updated:September 09,2020 11:29AM

The selection of low-voltage circuit breakers should pay attention to the following points.

  1. The rated current and rated voltage of the low-voltage circuit breaker should be greater than or equal to the normal working voltage and working current of the line and equipment.
  2. The limit making and breaking capacity of the low-voltage circuit breaker should be greater than or equal to the maximum short-circuit current of the circuit.
  3. The rated voltage of the undervoltage release is equal to the rated voltage of the line.
  4. The rated current of the overcurrent release is greater than or equal to the maximum load current of the line.

Using a low-voltage circuit breaker to achieve short-circuit protection is better than a fuse, because when a three-phase circuit is short-circuited, it is very likely that only one phase of the fuse will blow, resulting in phase-open operation. For low-voltage circuit breakers, as long as a short circuit is caused, the switch will trip, and the three will be cut off simultaneously. There are other automatic protection functions. But its complex structure, low operating frequency and high price make it suitable for demanding occasions, such as power distribution boards.

Common faults of low-voltage circuit breakers and their treatment methods are shown in the table.

Symptom

Cause

repairing method according to

manually broken

path is not closed

1. Low power supply voltage

2. Thermal trip bimetal Not cold

was restored

3. Undervoltage release or no voltage line

ring damage

4. Storage spring deformation, resulting in the closure

force is reduced

5. Counteracting the spring force is too large

1. Check the line and increase the power supply voltage

2. To be cooled before closing bimetal

3. Check the line, or replace the applied voltage

a coil

4. Exchange-spring

5. Re-adjust the spring reaction force

electrically operated broken

path is not closed

1. Does not match the power supply voltage

2. Power capacity is not enough

3. Solenoid enough stroke rod

4. Displacement motor-operated position switch

1. Power exchange

2. The operation of increasing the capacity of the power supply

3. Replacement or adjustment rods

4. Adjusting positioning switch

Motor start

breaker immediately

 

breaking when

 

1. Overcurrent release instantaneous setting value

too

2. A release walled parts damage

3. The reaction force spring release or rupture

down

1. Whole adjustment instantaneous value

2. Release or exchange damaged zero

means

3. Spring replacement or re-installed spring

Shunt trip

does not cause the circuit breaker

breaking

1. Shorted coil

2. Low power supply voltage

1. Exchange coil

2. Repair lines adjusted power supply voltage

undervoltage tripping

Noise Big

1. Counteracting the spring force is too

2. The working oil while the core

3. Short ring broken

1. Adjust reaction spring

2. Clear oil core

3. Exchange core

undervoltage tripping

can not make the interruption

breaking device

1. The reaction force becomes smaller spring force

2. The spring force accumulator spring break or

is small

3. Rust stuck mechanism

1. Adjusting spring

2. Or adjust the exchange-spring

3. Clear rust sewage


Related