How Do You Control The Speed Of An A/C Electric Motor?

How Do You Control The Speed Of An A/C Electric Motor

Your A/C electric motor is a device that normally runs at a constant speed. However, if you change the windings, frequency, or input voltage, the speed can vary. To change speed, the most efficient and common way is by frequency variance. As a power supply, an inverter is used.

With the development of (and decrease in) power electronics costs, frequency variance has become a popular method. Still used are various methods involving voltage reduction to the motor windings with motor winding taps, transformers, or resistors. They are the preferred and low-cost methods for some applications.

Power the AC Motor with an Inverter – What You’ll Need

For this job, you’ll need the following:

  • Motor with winding taps
  • Variable transformer
  • Variable resistor
  • Variable frequency inverter

Tackling Your Project

If you decided that you want to power your A/C motor with an inverter, here’s what you’ll need to do:

  • You need to pick the right inverter. It needs to be able to supply the current and motor voltage including the starting current.
  • Use the range of speed variation needed to pick the frequency range that the inverter has to supply. The frequency supplied to the motor will be varied, and the inverter controls will also vary the motor speed accordingly.
  • In the motor circuit, add a variable resistance if accurate speed control is not required and an inverter is too costly.
  • Normally close to zero, the motor “slip” will increase as the motor power supply is reduced and the motor poles don’t get adequate power to create the needed force to keep up speed at a normal pace. For high slip, the motor must be specifically designed. The circuit and resistance design are specific to the exact application.
  • If you desire reduced, high slip voltage speed control – which is more efficient – use a variable voltage transformer to alter the main winding voltage supply. Compared with the variable resistor, the variable voltage transformer has low losses.
  • To control the motor speed, the transformer may have a series of changeable taps or it might have a motorized tap changer. The motor speed changes, in either case, in small increments. For the installation where it is used, the detailed design is specific.
  • If applicable, to change the speed, use an A/C motor with tapped windings. In its main winding, this type of motor has a certain number of tabs that allow it to run with varied voltages applied to the magnetic field. For a particular motor, the number of speeds available and the number of taps are usually not in excess of four. In fans that have high, medium, and low speeds (and a switch selector), this method is common.

This speed control method is low-cost (the precise device speed is not crucial).

R & Y A/C Compressors® Carries Automotive A/C Parts

When you need to work on the air conditioning system in your vehicle, do what people have been doing for over 30 years. Count on the family-owned and operated company, R & Y A/C Compressors®.

Some of the parts we carry include the following:

  • Tubes
  • Valves
  • Condensers
  • Evaporators
  • Accumulators
  • Compressor bearings
  • Clutches
  • Condenser and compressor kits and more

To reach us, call 305-919-8864 or send us an email at [email protected].