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Monday, 01 June 2020 09:15

Why You Should be Using a Three Phase Induction Motor with Your AC Variable Frequency Drive (VFD)

A variable frequency drive (VFD) is a type of adjustable-speed drive used to control electric motors driven by an alternating current (AC). The two basic types of AC motors used in industries are synchronous and induction. There are several reasons why you should be using a three-phase induction motor with your VFD.

Related Blog: 5 Things You Need to Know Before Designing Your Motor Control Center


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Synchronous versus Induction Motors

Synchronous AC motors work using rotors that turn at precisely the same speed as the rotating magnetic fields. The motor requires a direct current (DC) source, to produce electricity flow into the stator windings, and create a rotating electromagnetic field. The complete interlocking between the stator, and the rotor’s rotating direction, determine that the motor runs synchronously or it doesn’t function at all.

Induction motors are the most common motors used for industrial machinery, such as pumps, conveyors, and blowers. They also work using electromagnetic fields, but are categorized by the number of “phases.”  Phase refers to the number of separate electric currents activating coils situated around the stator.

In a three-phase motor, three currents are used to energize three, or multiples of three, coils. Three-phase motors are self-starting and do not require an external DC source. The rotor speed in an induction motor varies, depending on the fluctuating magnetic induction, and this fluctuation results in the rotor turning at a lower speed than that of the stator’s magnetic field.  

 

What Conditions Impact the Rotor Speed of an Induction Motor?

  • Frequency of the AC supply
  • Number of coils that comprise the stator
  • Load on the motor

The higher the load requirements, the greater the difference (slip) between the rotor speed and the speed of the rotating magnetic field. To adjust the speed of the AC induction motor, the frequency of the AC supply must be altered, which is the purpose of a variable frequency drive.

ThreePhaseInductionMotor

Three Phase Induction Motor and VFD

Adding a VFD to a three-phase induction motor permits the speed of the motor to be altered in conformity with the motor’s load, saving energy. Voltage and frequency are provided in a precise method as the motor starts, also eliminating energy waste. Other advantages, include:

  • Increased lifespan for AC motor
  • Economical speed control
  • Lower maintenance than DC controlled motor

Three-phase induction motors have extensive uses in many industries, because they are self-starting, powerful, and efficient. Motors controlled with the help of VFD are the most efficient, smoothest running, and highest energy savers available.

If you have any questions about motors or want to speak with an expert about your options, contact Mader Electric today and speak with a member of our team.

Related Blog: Variable Frequency Drive (VFD) Frequently Asked Questions

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