Dual power automatic switching circuit! 4 kinds of dual power automatic switching circuit diagram connection method, classification

The application of automatic switching of dual power supply is very wide. First of all, let’s briefly look at how to use relays and contactors to achieve the purpose of automatic switching of power supply that can be achieved by dual power transfer switches.

一. Two contactors realize switching:
The coil of the backup power supply goes to the normally closed point of the main contactor, and the main power contactor pulls in the main circuit and conducts. The main power supply is cut off, and the backup power supply is turned on through the normally closed point of the main contactor. If the main power returns to normal, the backup power is disconnected. Of course, it can also be realized by contactor interlocking, which is a bit complicated, and what should I do when the main power supply and the backup power supply are powered at the same time? Therefore, the kind of work that needs to be connected in sequence, there is no need to be so troublesome, and the method is not unique.

二. One relay and two contactors:
The contactor coil of the main power supply is connected to the normally open contact of the relay, and the contactor coil of the backup power supply is connected to the normally closed contact of the relay. When the main line is powered, the relay is closed, the normally open contact is closed, and the main line is turned on. The normally closed contact is disconnected and the backup power supply does not work. When the main line is de-energized, the relay is also de-energized. The normally open contact returns to the initial disconnected state, and the main line is disconnected. The contactor of the backup circuit starts working through the normally closed contact of the relay.

三. Double changeover contact relay:
Similar to the above, except that this relay is a double changeover contact. When energized, the two sets of contacts are closed. The two sets of contacts are disconnected when the power is turned off. One electrical component can do it. If the A circuit is a single-phase 220V power supply, the coil voltage of the relay is also selected to be AC ​​220V. There is a time difference between the contactor and the relay when it is turned on and off, and there will be a short response to equipment or electrical appliances that require high power consumption. For example, the light bulb flickered significantly, and the motor stopped for a while. If it is a self-locking line, you will find that the electrical equipment does not work.

四. dual power switch:
This cost is a bit high and requires hands-on. If you have a strong hands-on ability, you can assemble a control circuit by yourself.
There must be a short time difference in power conversion, and it is impossible to achieve seamless connection without continuous power supply.

五. The distinction between PC level and CB level of dual power switch:
The dual power switch is divided into PC level and CB level, and the structure of the two is roughly the same. The PC level is an isolated type, like a double-throwing knife switch, plus an operating mechanism.
Class CB is a circuit breaker protection type, consisting of two circuit breakers plus an operating mechanism, with overload and short circuit protection, the same as circuit breaker protection. Users should consider the following aspects when choosing.
(1) Consider from the point of view of reliability.
The reliability of the PC-level is higher than that of the CB-level. The PC-level uses a mechanical + electronic conversion action lock, and the CB-level uses an electronic conversion action lock. Therefore, in some workplaces with relatively high security requirements, it is recommended to choose PC-level products.
(2) Consider from the perspective of switching time.
The switching time of the two products is different. PC-level products are more commonly used in geared motors, because the motor speed is high (16-22r/min), and after the circuit fails, it is necessary to wait for the motor speed to decelerate to a certain level to trigger the switch action mechanism to break. Open, the action time is relatively slow, although the switching time is slow, but as a mechanical product, it is more from the perspective of durability.
CB-level products are often used in residential buildings, where the faulty power supply is easy to disconnect and the switching time is fast.
(3) The PC-level dual power switch has no short-circuit protection function. Whether the user adds additional circuit breakers should be considered according to the needs of the circuit system.
The function of the dual power switch is to realize the conversion of dual power sources, and the presence or absence of short-circuit protection will not affect its operation. Many people think that the short-circuit function is used to protect the switch, which is a misunderstanding.
(4)The installation of isolating switches will occupy space, increase costs, and reduce reliability. It is recommended that the number of isolating switches in industrial power systems should be controlled, and there is no need to install isolating switches in residential floors.