Energy Efficient Motors

Energy efficient motors are most economical because these motors have higher efficiency than the conventional motors like EFF-1 and EFF-2. The economic production of the product is the need of the day, and therefore every industry is using the energy efficient motors. The major energy efficient motors are IE1,IE2,IE3 & IE4. In this post, we will discuss energy efficient motors and their applications.

Efficiency Classes of Energy Efficient Motors

The efficiency of the equipment is the prime consideration for the designer and the user. The efficiency of the equipment must be as high as possible to save the electricity. The efficiency is defined as the how efficiently the system convert the input electrical energy into other forms of energy. The losses occurs in the conversion process needs to be minimized for getting the higher efficiency.

A lot of research has been done to reduce the losses in the induction motor. As a result, the premium efficiency (IE3) and supreme premium efficiency (IE4) classes motors are available in the market.

About 30-40 % of the generated electrical energy worldwide is consumed by electric motors. Therefore, there is need of the day to improve efficiency of motors.

efficiency classes of motor- energy efficient motors

There are two types of the losses – Iron losses and copper losses- mainly occur in the induction motor.

Constant or Fixed Losses

The constant or fixed losses in the motor are voltage and the frequency dependable losses. The voltage and the frequency almost remain fixed so the losses on account of voltage and frequency- Eddy current and Hysteresis losses remain fixed. The fixed losses can be reduced by selecting the soft core material having high permeability. The losses can be reduced by designing the motor with low air gap length

Variable Losses

The variable losses depend on the loading of the motor. The higher loading on the motor leads to more slip, and the more copper losses. The resistivity of the winding material plays vital role in assessing the copper losses in the induction motor.  

The efficiency is defined as the ratio of output to input power.

Efficiency= Output (Power developed at the shaft)/Input (electrical power input)

= (Input-Losses)/Input
= 1-(Losses/Input)

If the losses are zero the efficiency is 100 %, however pragmatically it is not possible to achieve 100 % efficiency. If the efficiency of the motor is 90 %, it converts 90 % electrical energy into mechanical output and the balance 10 % of the electrical energy is dissipated as a heat.

Classifications of the efficiency classes as per IEC:

Standard IEC Line Motors (IEC 60034-30-1)

The new standard IEC 60034-30-1 replaces the standard IEC 60034-30:2008, which has defined three efficiency levels for three-phase induction motors to date. The updated standard IEC 60034-30-1 now includes the fourth efficiency level IE4. Furthermore 8-pole motors and an extended power range are now included in the standard.

In the IEC 60034-30-1 the following efficiency classes are defined for induction motors (IE = International Efficiency).

What is IE?

IE is “International Efficiency” with class 1, 2, 3 & 4 i.e. IE1 & IE2, IE3 & IE4.

IE efficiency class motors

IEC Efficiency Limits

The below-given chart shows the efficiency of the motor in different efficiency classes.

energy efficiency of IE1,IE2 and IE3 motors
comparision between efficiency class IE1,IE2,IE3 and IE4

How is Higher Efficiency achieved in Energy Efficient Motors?

The materials, mechanical and electrical design of the motor are the factors that affect the efficiency of the motor. Energy efficient motors are manufactured using the high quality material with an optimized design.

The following design considerations are adopted for energy efficient motors.

  • A large diameter copper wire is used for winding to reduce the resistance of the coils. The copper losses in the  motor get reduced with a reduction of the coils resistance.
  • Optimization of the air gap length to reduce the stray & magnetization losses. The power factor of the motor also gets improved with less air gap length. The overload capacity of the motor gets reduced with the reduction of the air gap length. Therefore, the driving load characteristics must be checked before installation of energy efficient motors.
  • An optimized cooling fan design to reduce the windage loss.
  • Thinner and higher quality steel lamination in the stator and rotor core reduce the core losses.
  • High quality bearings are used to reduce the friction losses.  

Calculation of cost saving in Energy Efficient Motor

annual saving in energy efficient motors- Formula
  • Hrs = Annual running hrs
  • kW= Motor rating in kW
  • % FL = Fraction of full load in running condition
  •  ηstd = Efficiency of standard Motor
  •  ηeff = Efficiency of energy efficient motor

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