Why should the contactor of the two speed fan be shorted

The two-speed fan completes the conversion and interlocking of the motor winding from the δ connection method to the double Y connection method through the short circuit of the contactor.

Two-speed fan refers to a blower equipment with two wind speeds, and the main factor that determines the wind speed is the speed of the fan. The fan can change the speed by changing the current or voltage. There are often two types: AC and DC.

The stator winding of the two-speed motor equipped with the two-speed fan is YY (or YY) connection, and the basic principle of speed regulation is to change the number of poles to achieve the purpose of speed regulation by changing the connection mode between the stator windings of the motor, and the mode is (or Y) when working at low speed, and YY mode when working at high speed. The circuit breaker, protection device and other electrical components equipped with the fan electrical control box must be correctly and reasonably selected according to the rated capacity of the fan.

For the working state of the high-rise basement at the usual exhaust and accident smoke exhaust speeds, the two-speed asynchronous motor is particularly suitable. When the two-speed fan is changed from low speed to high speed, the synchronous speed is increased a lot, and the exhaust air volume is also greatly increased, and the system is immediately changed from exhaust to smoke exhaust. However, in the design process, the electrical control problem of the two-speed fan will be encountered, that is, how to solve the conversion and interlocking of the motor winding from the δ connection method to the double Y connection method, and the automatic and manual control in the fire linkage; How to protect the shutdown of the fan in high-speed operation, how to maximize the reliability of accident smoke exhaust, how to ensure the power supply, etc.

In the case of a two-speed motor, that's when it runs in a double star shape! If it is a standard motor, the voltage is zero where it is shorted! The low-speed operation of the two-speed motor is triangular, which is very ordinary, and it is necessary to pay attention to a lot when the double star is shaped, and the wiring must be correct, otherwise there will be a lack of phase and the motor will be burned.

Ordinary motors are single star connections, and the voltage at the short circuit is also zero!

Large fans generally use two-speed motors.

You mean interlocks, right? Prevent three-phase short circuit.

Summary. Two contactors can be used to control high and low speed fans, but it is necessary to consider whether the rated current of the contactor can meet the current demand of high and low speed fans. If the current of the high and low speed fan is large, it is necessary to choose a contactor with a higher rated current.

In addition, it is also necessary to reasonably design the wiring method of the contactor to ensure the reliability and safety of the circuit. It is advisable to consult a professional electrical engineer when designing and installing.

Two contactors can be used to control high and low speed fans, but it is necessary to consider whether the rated current of the contactor can meet the current demand of high and low speed fans. If the current of the high and low speed fan is large, you need to choose a Shenliang contactor with a larger rated current. In addition, it is also necessary to reasonably design the wiring method of the contactor to ensure the wide number of runs and the safety of the circuit.

It is advisable to consult a professional electrical engineer when designing and installing.

Can you add, I don't quite understand it.

Two contactors can be used to control high and low speed fans, but it is necessary to consider whether the rated current of the contactor can meet the current demand of high and low speed fans. If the current of the high and low speed fan is large, you need to choose a Shenliang contactor with a larger rated current. In addition, it is also necessary to reasonably design the wiring method of the contactor to ensure the wide number of runs and the safety of the circuit.

It is advisable to consult a professional electrical engineer when designing and installing.

Generally, according to 2 large and 1 small considerations, to give an empirical statement, the contactor according to the motor power * 2 such as 11 two-speed fan to choose two 25A contactors and one 18A contactor.

Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), which are used in electricity, power distribution and consumption. Contactor in a broad sense refers to the electrical appliances that use the current flowing through the coil to generate a magnetic field and close the contact to control the load in industrial electricity. In electrical engineering, because it can quickly cut off the AC and DC main circuits and can frequently connect and high-current control (some types can reach 800 amperes) circuits, it is often used as a control object for motors, and can also be used to control plant equipment, electric heaters, working machine tools and various power units and other power loads, contactors can not only turn on and off the circuit, but also have a low voltage release protection effect.

The contactor has a large control capacity and is suitable for frequent operation and long-distance control. It is one of the important components in the automatic control system.

Follow the starting current of the motor to select it.

The two-speed motor is triangular when working at low speed, and a contactor is required. At high speeds, the double star connection method is adopted, which requires two additional contactors, so there are three in total.