What is the reason for the loud motor noise? What are the speed regulation methods and characteristics?

What is the reason for the loud motor noise? What are the speed regulation methods and characteristics?

 When the motor is running, we often encounter the situation that the motor is noisy, so what is the reason for the loud motor noise? Electric motors generate noise for two reasons: mechanical and electrical.

1. Mechanical aspects, such as damage to the motor or cooling fan, unstable fixation of the motor, etc. This situation is easy to deal with, generally as long as the source of the noise can be found.

2. Electrical aspects

(1) Motor resonance Sometimes, the motor will produce mechanical resonance in a certain frequency band during operation. In this case, the frequency hopping setting method of the inverter can be used. Inverters generally have a "frequency hopping" setting, which is used to set the frequency of motor resonance. When the inverter runs to this frequency band, it skips this frequency to avoid motor resonance.

(2) The bearing capacity of the motor is reduced. Sometimes the motor has been used for a long time, or the quality of the motor is not good, and the carrying capacity will be reduced. Here, the motor will be noisier than normal.

(3) If the carrier frequency of the inverter is too low, a higher carrier frequency can be set, but it will bring some problems. If the carrier frequency is set too high, it will cause interference to other devices, especially when using PLC communication. Therefore, the carrier frequency should be set according to the actual situation on site.

 (4) When the harmonic component of the frequency converter is large, it is easy to cause the motor vibration to become larger, the rotational speed jitter to be unstable, and the motor noise to become larger.

The motor can achieve the purpose of changing the speed by changing the power frequency f, the number of poles p and the slip s of the motor.

1. From the essence of speed regulation, different speed regulation methods are nothing more than changing the synchronous speed of the AC motor or not changing the synchronous speed. There are winding motor rotor series resistance speed regulation; chopper speed regulation; cascade speed regulation and application of electromagnetic slip clutch; hydraulic coupling; oil film clutch, etc. The speed regulation method that does not change the synchronous speed is widely used in production machinery.

2. From the perspective of energy consumption during speed regulation, there are two inefficient speed regulation methods: speed regulation means that the slip rate is unchanged, so there is no slip loss, such as multi-speed motors, variable frequency speed regulation and energy recovery The speed regulation mode of slip loss (such as cascade speed regulation, etc.). ).The speed control method with slip loss is low in efficiency, such as the rotor series resistance speed control method, the energy is lost in the rotor circuit; the speed control method of the electromagnetic clutch, the energy loss of the clutch coil; when the hydraulic coupling adjusts the speed, Energy is lost in the fluid coupling oil. In general, slip losses increase as the speed control range increases. If the speed control range is not large, the energy loss is small.

Synchronous speed can be changed by multi-speed motors that change the number of stator poles, variable frequency speed regulation that changes stator voltage and frequency, and speed regulation with or without commutated motors.