Three Principles of Short Circuit Protection

- Nov 10, 2019-

Three Principles of Short Circuit Protection


Most of the leakage circuit breakers are composed of small circuit breakers and leakage accessories. Small circuit breakers have only overload protection and short-circuit protection functions, while leakage circuit breakers have more leakage protection functions. How do these three functional principles form:

1. Overload protection (thermal buckling principle)

When the operating current exceeds the rated current, the bimetallic sheet has different thermal expansion coefficients, and the degree of elongation after heat is different, and the compresses are held together to contain each other and bend to trigger the detach.


2. Short circuit protection (magnetic buckling principle)

When a strong short-circuit current is generated, a strong magnetic field reaction occurs inside the coil, and the moving iron center moves forward to push the lock and trigger the buckle.


3. Leakage protection

When the zero-sequence Transformer detects the imbalance of the leakage current and reacts the information into the integrated block, the integrated circuit triggers the locking action by magnetic suction of the leakage detach in the instruction after analyzing the unbalanced current.

We need to know that the number of specifications are also factors we should consider.


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