Understand the working principle of shaded pole motor in three minutes
Shaded-pole motors are widely used in household appliances, such as hair dryers, electric fans, washing machine drain pumps, microwave oven cooling fans, vacuum cleaners, etc. Today, let's take a look at the working principle of shaded-pole motors.
(Note: This article requires a certain knowledge of electronics and electrical appliances)
Before talking about shaded pole motors, we first have a preliminary concept of motors. In essence, all motors are due to electromagnetic effects, so that the stator of the motor generates a rotating magnetic field, and the rotor of the motor is affected by the ampere force in the magnetic field. Rotational movement. We need to remember two things: The motor consists of a stator and a rotor, which generate a rotating magnetic field.
Shaded-pole motor is a single-phase asynchronous motor, that is, a motor with AC single-phase input, and the rotational speeds of the stator magnetic field and the rotor magnetic field are asynchronous. Taking an AC fan as an example, its structure is as follows:
When the power-on starts, a magnetic field is generated in the stator winding current, an induced magnetic field is generated in the iron core, and a part of the magnetic field is generated immediately when the circuit is turned on. Because of the characteristics of the alternating current, the magnitude and direction of the current change periodically, so this part produces a change. The magnetic field A, the magnetic field A causes the rotor to generate an induced current, so the rotor is affected by the Lorentz force in the magnetic field. However, the induced current generated by the rotor is symmetrical with the magnetic center line (and the axis line) as the center, so when the rotor is stationary, the induced current is equal in magnitude and opposite in direction. rotate.
At this time, the short-circuit ring plays a key role. The short-circuit ring will induce a magnetic field B that hysteres the change of the magnetic field of A. After design, the phase difference of the magnetic field B and A is close to 90°, so that the squirrel-cage cast aluminum rotor corresponds to the two sides of the rotor. The received Lorentz force is unbalanced, resulting in the initial rotation action, and because of the periodic changes in the magnitude and direction of the alternating current as mentioned above, the rotor is always in an unbalanced torque state and continues to rotate. In the equilibrium state of the Lenz force, the rotor will continue to rotate.
Sometimes, the electric fan doesn't turn, we just need to turn the fan blade, the electric fan can work normally, do you know the reason now?
(Knowledge about rotating magnetic fields will be updated in later articles, please pay attention: Brother E said electrons)
Application and Maintenance of Shaded Pole Motor
In our daily life, the cooling fans of refrigerators and clothes dryers, the drain pumps and electric fans of washing machines are usually shaded-pole motors. If the motor is damaged, when there are no motor parameters, we only need to install the two When AC power is connected to the terminal, the damage can be judged according to whether the motor is working.
When the electrical appliance does not work from time to time, then we must pay attention to whether the cooling fan is not working, causing the key parts to heat up and produce a protective action. The damage of some key parts usually requires repairing the core of the entire system, and the cooling fan on the home appliance can usually be done within 30 yuan, so once we find that the motor is abnormal, we must replace it in time. Don't lose the big because of the small.
The way to break the balance state, one is the shaded-pole motor explained in this article, which is the phase difference caused by the short-circuit ring (also known as the shaded-pole ring), and the other is the phase difference caused by the capacitor startup, that is, the capacitor startup Type single-phase asynchronous motor, the capacitor is widely used in washing machines, dryers, range hoods and other electrical appliances, and we will explain it later.
