The covered pole motor is a simple self-starting AC single-phase induction motor, which is a small squirrel-cage motor. One of the auxiliary coils is surrounded by a copper ring, also known as the covered pole ring or the covered pole ring, which is used as the secondary winding of the motor. The remarkable characteristic of the cover pole motor is that the structure is very simple, there is no centrifugal switch, the cover pole motor power loss is very large, the motor power factor is low, the starting torque is also very low. They are designed to remain small in size and have low power ratings. The speed of the motor is as accurate as the frequency of the power supply applied to the motor, which is often used to drive clocks. The cover pole motor only rotates in a specific direction, the motor is impossible to rotate in reverse, the loss caused by the cover pole coil, the motor efficiency is low, and its structure is simple. These motors are widely used in household fans and other small capacity appliances.
Working principle of hood pole motor：The covered pole motor is an AC single-phase induction motor. The auxiliary winding is composed of copper rings, called covered pole coils. The current in the coils delays the phase of the magnetic flux at the magnetic poles in order to provide a rotating magnetic field, and the direction of rotation is from the non-covered pole to the covered pole ring.
The dome coil (ring) is designed to deflect the axis of the magnetic pole away from the axis of the main pole, the field coil and the additional dome coil to generate a weak rotating magnetic field. When the stator is energized, the magnetic flux of the magnetic pole body generates a voltage in the covered pole coil, which acts as the secondary winding of the transformer. The current in the secondary winding of the transformer is not synchronized with the current in the primary winding, and the magnetic flux in the cover pole is not synchronized with the magnetic flux in the main pole.
In a covered pole motor, the rotor is placed in a simple C-core, and half of each pole is covered by a covered pole coil, which generates pulsating magnetic flux when AC current is passed through the supply coil. When the magnetic flux through the blackout coil changes, voltage and current are induced in the cover pole coil, which corresponds to the magnetic flux change from the power coil. Thus, the magnetic flux under the dome coil lags behind the flux in the rest of the coil. A small rotation is generated by the rotor in the flux, so that the rotor rotates. The following figure shows the flux line obtained by finite element analysis.
Cover pole motor structure：The rotor and its associated reduction gear train are enclosed in an aluminum, copper or plastic housing through which the enclosed rotor is magnetically driven. These gear motors typically have a final output shaft or gear that rotates from 600 RPM to 1/168 RPM (1 RPM per week). Because there is usually no clear starting mechanism, by the constant frequency power supply of motor rotor must be very light, so that you can in a cycle power frequency to achieve speed, the rotor can be equipped with squirrel cage, like induction motor makes the motor start, once the rotor to be pulled to its magnet synchronous, no induced current in the cage, so no longer play a role in the operation, The use of variable frequency control allows the cover pole motor to start slowly and deliver more torque.
