The centrifugal fan is a DC type speed regulating motor. The speed of the speed is to change the conduction angle of the thyristor through the adjustable resistance, and then the voltage controlled by the thyristor to reach the two ends of the motor to achieve the purpose of controlling the speed. The motor speed is unstable. From the principle analysis, the following four situations are possible.

(1) One of the four rectifier diodes has only a problem

(2) There is toner or carbon brush between the rotor and the commutator. It is difficult to repair. Firstly, the adjustable resistor is measured. The resistance value changes regularly with the adjustment. It proves that the potentiometer is Ok, there is no problem in measuring the thyristor. Since the diode is a high-current gold-sealed tube, the screw on one end is fastened to the circuit board, and the other end is soldered to the circuit board and removed from the circuit board. It was found that the positive and negative poles were loose, and then the side was shaken while measuring, confirming that the diode was good or bad.

(3) There are also many problems with thyristors, usually breakdown short circuit, open circuit, unable to trigger or poor internal contact.

(4) Adjustable resistance, the cabinet type centrifugal fan is installed on the control panel due to the adjustable resistance. The frequency of use is very high, and the time is long. The situation of poor contact is very common. If you find that the fan is unstable during the operation, you may wish to use the four points mentioned above as the troubleshooting direction to quickly find out the cause and improve the efficiency of maintenance.

The fan produced by the company is widely used in industrial and mining enterprises such as railways, highways, bridges, tunnels, metallurgy, chemical industry, shipbuilding, oil refining and food, etc., because of its new structure, low noise, excellent performance and stable operation. It is also suitable for underground shopping malls and warehouses. Cooling, ventilation, ventilation, fire and smoke exhaust for hospitals and civilian high-rise buildings.