How to choose the Earth Leakage Circuit Breaker with appropriate specifications?

- Apr 05, 2020-

How to choose the Earth Leakage Circuit Breaker with appropriate specifications?




 

Case description:
The customer responded that the 63A Earth Leakage Circuit Breaker produced by our company was short-circuited and not tripped.

 

Process analysis:
1. Take our products to the laboratory for testing, according to national standards:
The trip through 5 times the current (63 * 5 = 315A) is greater than 0.1 seconds. The trip through 10 times (63 * 10 = 630A) is less than 0.1 seconds. Conclusion: qualified

 

2. Simulation test:

a) Use a 4-square wire of 1 meter Short-circuit directly and trip immediately.

b) Use a 4-square wire of 10 meter Short-circuit directly, will not trip immediately

 

3. Analysis and explanation: There are several factors affecting whether the product trips:

a) Specifications of the Earth Leakage Circuit Breaker’s current: 63A (63 * 7 = 441A), 40A (40 * 7 = 280A), 32A (32 * 7 = 224A), etc. If the short-circuit current is 300A, then the 63A Earth Leakage Circuit Breaker does not trip.

 

b) It is related to the resistance of the entire circuit: I = U / R When R = 1 ohm, the voltage is 220V and the current is 220A, and the size of R is related to the length and diameter of the wire. Generally, 63A leakage switches are required to use 6 square wires (see table for details)

Recommended cross-sectional area of wire under different currents

Rated current (A)61016-202532-405063

Cross-sectional area of wire

(mm2)
11-1.51.5-2.52.5-44-66-86-10


Solution: 

1. Our products are qualified after inspection.

2. It is recommended that customers choose an earth leakage circuit breaker with a suitable specification (in recent years, many customers believe that the larger specification of earth leakage circuit breaker is safer, which is incorrect)

 

How to choose the leakage switch with appropriate specifications?

I=P/U   I:current        P:power     U:voltage

For example:

Xiaoming's house has two 1P air conditioner, one 3P air conditioner, one 2000W electric water heater, one 1500W electric heater, two 250W computer, one 1500W induction cooker, and refrigerator, TV, lighting, washing machine, hair dryer and so on, When it is expected to be 2000W, how appropriate is the Earth Leakage Circuit Breaker at home? 

P=(1+1+3)X750+2000+1500+250X2+1500+2000=11250W

I = P / U = 11250/220 = 51A  

Considering that all electrical appliances will not be used at the same time, take a coefficient of 0.8, 51X0.8 = 40A   

40A is appropriate for the Earth Leakage Circuit Breaker.

 

The misunderstanding of the use of circuit breakers:

1 Must be action reach the rated current

2 Must be action when short-circuit

3 Incoming line up and down

4 The leakage circuit breaker should be action when it thunders

5 The earth leakage circuit breaker must be action when people get an electric shock