Building electrical – dual power switching principle


(4) The installation of disconnectors will occupy space, increase cost and reduce reliability.

When energized, the two groups of contacts are closed.

The main power supply is powered off, and the standby power supply is connected through the normally closed point of the main contactor.

When the main line is energized, the relay is pulled in, the normally open contact is closed, and the main line is turned on.

When the main line is de energized, the relay is also de energized.

It has overload short-circuit protection, which is the same as circuit breaker protection.

If it is a self-locking line, you will find that the electrical equipment does not work.

PC grade products are widely used on reduction motors because of the high motor speed (16-22r / min).

Lifting Anchor

Let’s take a brief look at how to use relays and contactors to realize automatic switching.

The coil of the two contactors to switch the standby power supply goes to the normally closed point of the main contactor, and the main power contactor is pulled in and the main circuit is connected.

Whether there is a short-circuit protection function will not affect its operation.

There must be a short time difference in power conversion, and it is impossible to achieve seamless connection between continuous power.

For example, the light bulb obviously flickered and the motor stopped.

One electrical component can be completed.

Contactors and relays have time difference when switching on and off, which will have a short response to equipment or appliances with high power requirements.

The normally closed contact is disconnected and the standby power supply does not work.

Two sets of contacts are closed when power is off.

Whether users add additional circuit breakers should be considered according to the needs of the circuit system.

Therefore, in some work sites with high safety requirements, it is recommended to choose PC level products.

The cost of dual power transfer switch is a little high and requires manual operation.

CB products are commonly used in residential buildings.

The double change-over contact relay is similar to the one above, except that the relay is a double change-over contact.

After circuit failure, it is necessary to wait for the motor speed to decelerate to a certain extent to trigger the switch action mechanism to disconnect.

If circuit a is a single-phase 220 V power supply, the coil voltage of the relay also adopts AC 220 v.

One relay two contactors, the contactor coil of the main power supply goes through the normally open contact of the relay, and the contactor coil of the standby power supply goes through the normally closed contact of the relay.

Distinction between PC level and CB level of dual power supply switching switch dual power supply switching switch is divided into PC level and CB level, and their structures are roughly the same.

If a friend with strong hands-on ability can assemble a control circuit by himself.

(1) From the perspective of reliability, the reliability of PC level is higher than that of CB level.

It is recommended that the installation quantity of disconnectors in industrial power system should be controlled, and it is not necessary to set disconnectors in residential floors…

The PC level is isolated, just like a double knife switch and an operating mechanism.

The dual power switch is used to realize the conversion of dual power supplies.

The normally open contact returns to the initial disconnected state and the main line is disconnected.

Users should consider the following aspects when selecting.

PC level uses mechanical + electronic conversion action lock, and CB level uses electronic conversion action lock.

The action time is relatively slow.

The fault power supply is easy to disconnect and the switching time is fast.

The contactor of the standby circuit starts working through the normally closed contact of the relay.

Although the switching time is slow, as a mechanical product, it is more considered from the perspective of durability.

Of course, it can also be realized by contactor interlocking, which is a little troublesome, and what if the main power supply and standby power supply are powered at the same time? Therefore, there is no need to be so troublesome and the method is not the only one.

CB level is circuit breaker protection type, which is composed of two circuit breakers and operating mechanism.

(3) The PC level dual power switch has no short-circuit protection function.

Dual power switching is widely used.

If the main power supply returns to normal, the standby power supply is disconnected.

Many people think that the short-circuit function is used to protect the switch, which is a misunderstanding.

(2) From the perspective of switching time, the switching time of the two products is different.

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