What is the fundamental cause of noise in DC fans?

What is the fundamental cause of noise in DC fans?

1. Vibration

When the rotor of a DC fan motor is running, if the physical centroid of the motor rotor and the inertial force core of the drive shaft are not on the same axis, it is easy to cause instability of the motor rotor. The close distance between the centroid of the motor rotor and the core of the shaft inertia force is called eccentricity. The instability of the motor rotor can also lead to axial force. When the motor rotor rotates, centripetal force creates a force at the shaft support point, generating vibration that is transmitted to all components of the equipment.

2. Wind noise

When a DC fan is working, the leaves will periodically be subjected to uneven single pulse forces from the inlet and outlet air rotation, causing noise. On the other hand, due to the uneven distribution of pressure between the leaves themselves and between them, rotational noise is also formed by the impact on surrounding gases and components during rotation. In addition, when the vapor flows through the leaves, it also generates seepage barriers, vortices, and vortex separation, causing pressure distribution pulses on the leaves and vortex noise. The noise generated by these three reasons can be called "wind shear noise". Generally, centrifugal fans with high exhaust volume and pressure produce significant cutting noise.

3. Abnormal noise

The DC fan message sounds like a single message, but the abnormal noise is different. During the operation of the fan, in addition to the message, if there are other Chinese noises, we can make a judgment that a fan sound is abnormal. The buzzing sound may be caused by cultural collision due to the lack of dirt or deformation of rolling bearings, improper assembly methods, uneven winding of motor windings, which may lead to loosening and abnormal noise.

4. Usage period

The service life of a DC fan refers to the normal operating time of the heat pipe radiator. The service life of high-quality products can generally reach hundreds of thousands of hours. Because the price and characteristics are similar, choosing products with a long service life can obviously better maintain our own project investment. The service life of a centrifugal fan is composed of many factors such as motor life, software environment, and power environment.

What are the differences between DC fans and AC fans?

1. The principle is different

A DC fan is driven by the magnetic effect of AC voltage and current, which converts electromagnetic energy into mechanical kinetic energy and drives the fan blades to rotate. With the continuous conversion of electromagnetic coils and ICs, the magnetic induction core drives the fan blades to rotate.

AC fans are driven by alternating current, and the working voltage alternates between positive and negative poles, without the need for circuit control, resulting in an electromagnetic field.

2. Different material properties

DC fans are made of plastic materials, and the internal structure of DC power includes transformers and main control chips (including frequency conversion circuits, rectification and filtering, operational amplifiers, etc.), which are not easily affected by voltage fluctuations, so their service life is long.

The construction of AC fans is dominated by transformers, and most AC fans use domestically produced discharge needles, usually tungsten needles or stainless steel plates. If the working voltage fluctuates too much, it will affect the service life of the transformer.

3. Different structural composition

The motor rotor of a DC fan includes DC cooling fan blades, which are the driving force for air convection. The fan pivot is used to balance the rotation of the fan blades. The motor rotor core is made of permanent magnet material, which promotes the conversion of magnetic levels and speed ratio. The magnetic core frame is fixed without moving the magnetic core.