Circuit breaker operating mechanism basic requirements

Update date:2018-05-28 Source:MAXGE

The effective and reliable operation of the circuit breaker depends to a large extent on the performance and quality of the operating mechanism. Therefore, according to the different circuit breakers, the operating mechanism provided by the circuit breaker should meet the required properties and reliability. The following are the main points:


1, should have enough closing function

In actual work, the energy of the operating mechanism will not remain at the rated value but will change within a certain range. According to the power-related regulations, the lower limit is 80-85% of the rated value, and the upper limit is 110% of the rated value. That is to say, when the operating mechanism is at the lower limit value, the short-circuit current can be opened and the upper limit value can be opened. When it does not, the related components should not be damaged due to excessive operating force. Moreover, when a short-circuit fault occurs in the power grid, the short-circuit current in the circuit can reach 40 kA, or even more, and the circuit breaker can withstand more than several kilo- kilowatt-hours of electric power. The operating mechanism must overcome such a large amount of electric power to close the circuit breaker. 

2, should have to maintain the closing function

In order to reduce the overall size of the circuit breaker and reduce energy consumption, the closing coil is designed to work for a short time, allowing only a short period of time to switch on the current, if the power is too long, it will burn the closing coil. This requires the operating mechanism to remain in the closing position after the closing coil is de-energized.


3, with a shorter opening time

The opening of the circuit breaker means that the circuit must be opened and an arc must occur. The larger the current to be broken, the more difficult it is to extinguish the arc and the harsher the working conditions. When a short-circuit fault occurs, the short-circuit current is much larger than the normal load current. As the system is short-circuited, the system circuit acts as an inductive circuit. Therefore, when the AC current crosses zero, the circuit breaker contacts the momentary contact, and the contact between the moving and static contacts Voltage cannot be mutated and transient recovery voltage will appear. In order to achieve the purpose of breaking the circuit, the operating mechanism must provide a certain opening speed, especially the rigid speed.

4, to have anti-skipping device

In order to avoid the phenomenon of consecutive multiple splits after the circuit breaker is closed, mechanical or electrical methods must be used to make the circuit breaker not open and close after being opened to reduce unnecessary actions.


5, to have linkage device

The interlocking device in the operating mechanism can ensure the reliability of the circuit breaker. When the circuit breaker is in a state, it will not be affected by the misoperation of the operating mechanism. Generally, the operating mechanism should have the interlocking position, low pressure and High pressure interlock, position interlock in spring mechanism, etc.

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