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Meaning Of Symbols On Molded Case Circuit Breaker

Views: 23     Author: Site Editor     Publish Time: 2022-09-05      Origin: Site

Circuit breakers are widely used components in medium and low voltage distribution lines and low voltage control lines. There are also many types of circuit breakers. Today, we take molded case circuit breakers as an example to briefly talk about the specific meanings of the various symbols above, so that everyone can choose circuit breakers correctly.

The Meaning Of Various Symbols On Molded Case Circuit Breakers

Molded case circuit breakers also have short-circuit protection and overload protection functions. At the same time, in order to protect personal safety and the safe operation of power equipment, it can also be used in conjunction with leakage protectors and measurement modules. It is used in low-voltage power distribution lines. For the main switch or branch switch, we can see a lot of information about various parameters of the circuit breaker on the molded case circuit breaker, which also provides convenience for us to use the circuit breaker correctly.

Take CSQ's HYCM1-250L/3300 As An Example

The symbols and parameters of the molded case circuit breaker are as follows:

Molded Case Circuit Breaker

HYCM1-250L/3300 is the product model of the circuit breaker, the specific meaning is shown in the figure:

HYCM1 250L 3300

* HYC: Enterprise code

* M: Molded case circuit breaker

* 1: Design code

* 250: Frame rating rated current (not the rated current of the circuit breaker)

* L: Breaking capacity feature code: L-Standard type, M-Middle high breaking capacity type, H-High breaking capacity type

* 3300: The first 3 in the back means that the number of poles is 3, the second 3 means that the release mode is a compound release (overload protection and short circuit protection), the last two digits are accessories, and 00 means no accessories.

* N: The rated working current of the circuit breaker, specifically this circuit breaker is 250A.

* Ii : The rated instantaneous short-circuit current setting value, the circuit breaker is 10In

It can be understood that when a short-circuit fault occurs and the current of the circuit breaker reaches 10 times the rated current, the circuit breaker will trip instantly.

* Ui: Rated insulation voltage

* Uimp: Rated impulse withstand voltage

The rated insulation voltage can be understood as the voltage at which the circuit breaker frame can be used normally, and breakdown may occur if the voltage exceeds this voltage.

The rated impulse withstand voltage can be understood as the short-term high voltage that the circuit breaker can withstand without breakdown.

* F: Refers to the working frequency, here is the power frequency 50Hz.

* Cat A: Indicates that the circuit breaker is used in category A.

A means that there is no selective design for short-circuit conditions, that is, it will trip when the short-circuit instantaneous current is reached. It is mainly used for the distribution box.


Table B is not specially designed for short-circuit conditions, such as short-circuit and disconnection.

The red button is the reset button, press the circuit breaker to trip.

* 1 3 5:Incoming Line

* 2 4 6:Load Side

* Ue: the rated working voltage, which is the voltage in the actual circuit.

* Ics:  Use Breaking Capacity

* Icu: Ultimate Breaking Capacity

It can be seen that at 400V, these two values are 26KA and 35KA respectively.

This breaking capacity refers to the ability of the circuit breaker to safely cut off the fault current, and the ultimate short-circuit breaking capacity is the maximum limit that can break the circuit breaker. After the circuit breaker can no longer be used: and the operating short-circuit breaking capacity is the ability of the circuit breaker to continue to be used after breaking.

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