Distinguishing knowledge of circuit breaker, contactor and relay in power system

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In the power system, circuit breakers, contactors and relays seem to be familiar guys, but many of them are not clear about the differences and connections between them. Let's talk about them today.

Say the same thing first!

Of course, there's no denying that these guys are all switch appliances. What's switch? It's easier to understand. All the switches that can complete one on one close action are switches. Therefore, these things are switches.

Therefore, these so-called differences, that is, the different switch forms.

1、 Circuit breaker

Its definition is very simple: it refers to the switch device that can close, carry and open the current under the normal circuit condition and can close, carry and open the current under the abnormal circuit condition within the specified time.

2、 Contactor

Contactor refers to the electric appliance which uses coil current to produce magnetic field and make contact closed to control load.

3、 Relay

Relay is a kind of electrical control device. When the change of input quantity (excitation quantity) reaches the specified requirements, it makes the controlled quantity change step by step in the electrical output circuit

Circuit breakers and relays are used in the primary electrical circuit, which can make and break large current, while relays are used in the secondary electrical circuit, with small contacts, which can only make and break small current.

So what's the difference between a circuit breaker and a contactor?

It is a typical application of motor forward and reverse control. As you can see, the circuit breaker plays the role of protecting electrical over-current, over-voltage, etc., but the contactor controls the operation of motor after connecting the coil according to different start signals.

In short, the power system is also very simple, mainly including power supply, transformer, conductor, electrical equipment and switch. All complex circuits can be divided into the above four parts.

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