How do single phase AC induction motors start in everyday home appliances?

In summary: They use a single phase power supply and have a main winding and a shaded pole or secondary winding. The shaded pole causes a phase shift in the magnetic field, creating a rotating magnetic field. This allows the motor to start and run without the need for a centrifugal switch or capacitor. However, some home induction motors may still use a capacitor to improve performance and reduce noise interference.
  • #1
Adenitz
1
0
Hello to all,

I'm a student of electrical engineering. We have learned the basics about AC induction motors and we learned that single phase motor cannot start by itself. There must be some additional part that will produce phase lead or lag in order to create rotational magnetic field. That is clear to me. Furthermore we have learned that these AC motors have either run winding or run capacitor that is disconnected later via centrifugal switch. However, I wonder how this is done in everyday home induction motors like hair dryers kitchen mixers and similar? I don't believe they have centrifugal switch built in somewhere.
Can you give me example how single phase AC motors start in home applications?

My best guess is that these motors have run windings permanent built in and there is no anything like centrifugal switch. I thought that capacitor is used for this purpose since I have found one when disassembling a hair dryer, but my friend told me that this capacitor is not for start but for preventing EMC interference with other devices like TV. He told me that this capacitor faild and that he short circuited it and motor worked without any problems.

Can you clarify these things for me?

Thank you
 
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  • #2
These type of motors are called http://en.wikipedia.org/wiki/Shaded-pole_motor" .
 
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Related to How do single phase AC induction motors start in everyday home appliances?

1. How does an AC induction motor start?

An AC induction motor starts by using a starter circuit to generate a rotating magnetic field within the motor's stator. This rotating field induces a current in the rotor, causing it to also produce a magnetic field. The interaction between these two fields creates torque, which causes the rotor to start rotating.

2. What is the difference between direct-on-line and soft start methods for AC induction motor starting?

Direct-on-line starting involves connecting the motor directly to the power source, resulting in a high inrush current and sudden acceleration. Soft start methods, on the other hand, use devices such as variable frequency drives or soft starters to gradually increase the motor's speed and reduce the inrush current.

3. What factors can affect the starting torque of an AC induction motor?

The starting torque of an AC induction motor can be affected by the motor's design, the type of load it is connected to, and the voltage and frequency of the power supply. Additionally, the use of a soft start method can also impact the starting torque.

4. What is the purpose of a starting capacitor in an AC induction motor?

A starting capacitor is used in single-phase AC induction motors to provide an additional phase shift, which helps to create a rotating magnetic field and start the motor. This is necessary because single-phase power supplies do not produce a rotating magnetic field on their own.

5. What are the common problems that can occur during AC induction motor starting?

Some common problems that can occur during AC induction motor starting include high inrush currents, motor overheating, and mechanical stress on the motor's components due to sudden acceleration. These issues can be mitigated by using soft start methods and properly sizing the motor for the intended application.

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