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What are the main parameters of MCCB
Date：2020-05-20
(1) rated voltage
The rated voltage on the circuit breaker nameplate refers to the rated voltage of the main contact of the circuit breaker, which is the voltage value to ensure the long-term normal operation of the contactor contact.
(2) Rated current
The rated current on the contactor nameplate refers to the rated current of the main contact of the circuit breaker, which is the current value to ensure the long-term normal operation of the contactor contact.
(3) tripping current
The tripping current is the current setting value that makes the over-current release act. When the circuit is short circuited or the load is overloaded seriously, and the load current is greater than the tripping current, the main contact of the circuit breaker will break.
(4) overload protection current and time curve
The curve of overload protection current and time is inverse time characteristic curve. The larger the overload current is, the shorter the action time of thermal release is.
(5) rated voltage of under voltage release coil
The rated voltage of under voltage release coil must be equal to the rated voltage of line.
(6) rated voltage of shunt release coil
The rated voltage of shunt release coil must be equal to the control power supply voltage.
(7) rated limit short circuit breaking capacity ICU
There are two indexes of breaking capacity of circuit breaker: rated limit short-circuit breaking capacity ICU and rated operation short-circuit breaking capacity ICs.
The rated limiting short-circuit breaking capacity ICU is the limiting parameter of the breaking capacity of the circuit breaker. After breaking several short-circuit faults, the breaking capacity of the circuit breaker will decrease.
Rated operation short-circuit breaking capacity ICs is a breaking index of circuit breaker, which can ensure its normal operation after breaking several short-circuit faults.
For moulded case circuit breakers, if ICs is greater than 25% ICU, they are qualified. Most of the ICs of circuit breakers in the market are between (50% - 75%) ICU.
(8) current limiting breaking capacity
Current limiting breaking capacity refers to the ability to limit fault current when circuit breaker trips in case of short circuit. When a short circuit occurs in the circuit, the contact of the circuit breaker will open quickly and generate an arc, which is equivalent to a rapidly increasing arc resistance in series in the circuit, thus limiting the increase of fault current, reducing the adverse effects of electromagnetic effect, electric effect and thermal effect of short circuit current on the circuit breaker and electrical equipment, and prolonging the service life of the circuit breaker. The shorter the breaking time of circuit breaker, the better the current limiting effect and the closer ICs is to ICU.
(9) tripping characteristics of miniature circuit breaker
The tripping characteristics of circuit breaker are divided into a, B, C, D, K, etc., and their respective meanings are as follows:
Type a tripping characteristic: the tripping current is (2 ~ 3) in, which is suitable for protecting semiconductor electronic circuits, measuring circuits with small power transformer, or systems with long circuits and small short circuit current;
Type B tripping characteristics: the tripping current is (3 ~ 5) in, which is suitable for household power distribution system, household appliances protection and personal safety protection;
Type C tripping characteristic: the tripping current is (5 ~ 10) in, which is suitable for protecting distribution lines, lighting lines and motor circuits with high switching current;
D-type tripping characteristic: the tripping current is (10 ~ 20) in, which is suitable for protecting equipment with high impulse current, such as transformer, solenoid valve, etc;
K-type tripping characteristic: it has 1.2 times of thermal tripping action current and 8-14 times of magnetic tripping action range, which is suitable for protecting motor line equipment, and has high anti impact current ability.
