Safeties of MCCB:

A molded case circuit breaker is used between MCB and ACB ratings as 16 Amp to 1600 Amp. It is available in thermal magnetic protection and microprocessor protection as overload, short circuit, earth fault.

1- Overload or long type::

Overload safeties are used in molded case circuit breakers for the present load as per capacity. Load capacity can be adjusted as per the present load.

If the MCCB breaker capacity is 250 A then it can be settled as 100-250 Amp. Running load is 250 amp then additional overload setting.9 to 1. Can be selected.

1- Load pick up setting:

.4, .5, .55, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 1.0
Trip time is adjusted as per site or load requirement. Time setting details are given below mentioned.

2-Load output setting:

it is available as--
.9 to 1. .9, .91, .92, .93, .94, .95, .96, .97, .98, 1.

2- Short circuit or short time:

Short circuit safeties are used in air circuit breakers for occurring a major fault like as phase to phase and phase to earth then a lot of current will be produced. So, the current value is multiplied by the breaker current rating.

1-Load pick upsetting:

1.5 to 10 times or multiply of rating of current (Ir value).
1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10.
For Example:-
If the ACB rating is 250 A Then we will have to set 3 to 4 times as default value.

2-Time Delay:

Trip time is adjusted as per site short circuit possibilities. Time setting details are given below mentioned.
it is available as 20 milliseconds to 600 milliseconds.
60, 100, 150, 300.
Default time delay setting is 300 milliseconds.

3- Instantaneous short circuit:

If a fault is large then the air circuit breaker will be tripped quickly or instantaneously. No time delay is required for tripping because the fault is major.
So, the breaker will be tripped instantaneously.

1-Load pick upsetting:

2 to 16 times or multiply of rating of current (Ir value).
2, 3, 4, 6, 8, 10, 12, 14, 16.
For Example:-
If the MCCB rating is 1000 A Then current can be calculated as.....
2 x 1000= 2KA.
3 x 1000= 3KA.
4 x 1000= 4KA.

4- Earth fault:

Earth fault safeties are used in air circuit breakers for current leakage in the ground. It can be calculated as how many percent of leakage current is with the ground. It can be 10 percent to 50 percent.

1-Load pick upsetting:

1 to.5 multiply of breaker current rating (Ir value).
.1, .2, .3, .4, .5,
For Example:-
Amp = 200 A.
leakage current = 20%.
Calculation is: 200 x .2 = 40 Amp leakage current.

2-Time Delay:

Trip time is adjusted as per site short circuit possibilities. Time setting details are given below mentioned.
• It is available as 100 milliseconds to 400 milliseconds.
100, 200, 300, 400.
Default time delay setting is 300 milliseconds.

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