Induction Motor Basics

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Induction Motor Basics Select Electrical

Electric motors are a vital component of industrial equipment, vehicles, appliances, and just about every piece of machinery that incorporates movement. An induction motor converts electrical energy into mechanical energy. Electric motors are powered by either AC or DC sources. Blowers, Pumpjacks, compressors and cranes are just a small handful of common machines that use an electric motor.

Today, we are going to look at the advantages of using a soft starter for your AC induction motor start-up.

About Induction Motors

In an induction motor (also referred to as a synchronous motor) is one of the main types of AC electric motors used in commercial and industrial environments. These motors are made up of a stator, or stationary windings and the rotor and work on the principle of electromagnetic induction. Applied voltage in the stationary windings creates an electro-magnetic field. Due to the way the stator windings are arranged a magnetic field appears to rotate around the inside of the motor housing. the rotor follows the rotating field in the stator causing rotation. In short, the power is transferred to the rotor winding by the stator through induction. There are two main types of induction motors — single-phase induction motors and three-phase induction motors.  

 

Single PhaseSelect Electrical WEG Induction Motor

Single-phase induction motors are mainly utilized in household applications like fans, refrigerators, grinders, and air conditioners. This is due to the low starting torque required whereas, three-phase motors are widely used for industrial applications. These motors function by the magnetic field made by only a single-phase power supply that  “pulsates” between 2 motor poles. As there is only one AC current producing two magnetic field states the single phase motor only approximates a rotating field, but not completely. These motors must be given an initial helping hand or feel a force “out-of-phase” with the stator phase for the initial movement of the rotor to occur. The stationary rotor will not feel any effects from this pulsating “up-down” magnetic field if it not already moving, as the up-down magnetic forces cancel each other out perfectly. Motor starters solve this issue by adding an out-of-phase influence which then creates a simulated rotating magnetic field to start the motor.

Single Phase Motors are simple in construction and inexpensive to manufacture relative to three phase motors. Single phase motors are used for lower power requirement applications, offer limited starting torque, and have low power factors when compared to three phase motors.

 

Three Phase

A three-phase induction motor is one of the most widely used electric motors and is an integral part of close to 80% of industrial applications. Three phase motors provide operational efficiency, rugged construction and smooth power supply that are necessary in an industrial setting.

Like any regular induction motor, this motor also comprises of a stator and a rotor. A “stator’ is a stationary element of an induction motor that consists of a cylindrical frame that carries the core of the rotor. This piece features different slotted stampings to carry three-phase windings. These windings in the stater have 120 degrees of separation. The rotor is of course the rotating part of the motor, featuring laminated cylindrical slots with copper or aluminum conductors that have joined ends. The two common classifications of motor are Phase Wound (Wound Rotor) Motors and Squirrel Cage . 

 

Squirrel Cage Three Phase Induction Motor 

Squirrel Cage motors are so-named due to the resemblance of the rotor to a squirrel cage. Some of the benefits of the squirrel cage induction motor include:

  • Inexpensive
  • Easy to maintain (reliable)
  • Excellent speed regulation
  • Compact & Lightweight
  • High efficiency output
  • Increased heat release (do not get as hot)
  • Zero risk of explosive accident

These motors are available in sizes ranging from < 1 kw to greater than 10,000 watts. Factors such as simplicity, rugged construction as well as constant speed and different load sizes have contributed to the popularity. 

Induction motors are commonly used in conjunction with a VFD (variable frequency drive) to help take the stress of start-up, increase efficiency, and prolong the life of the induction motor.

Have Questions About Induction Motors?

Select Electrical has the knowledge and experience to answer your question. To finite more, or if you have any inquires regarding our products, fill out our contact form, give us a call (780-968-8859), or connect with us on LinkedIn. We will work together with you to ensure the right products and motors for your specific system.