Energy Efficiency

Energy Efficiency and Electric Motor Efficiency Classes

The goal of the energy efficiency is to use less energy required to provide the same services and products.

Electrical motor efficiency is the ratio between the mechanical output power and the electrical input power:

The energy losses at electric motors are rotor and stator winding losses, iron losses, loses due to friction and fan which are converted into heat. An electric motor with a proper size and high power which operatesin its high efficiency region must be chosen for a high efficient system.Electric motors are designed to operate at nominal powers efficiently. Efficiency decreases by using electric motors with power higher or lower than nominal power. Meanwhile using inverter with electric motor is necessary to increase efficiency. AC motors starting currents are 6-7 times the nominal currents, which causes high energy loses. It is advantageous to allow the electric motor to operate with a speed control device. A Stop-and-Go-Operation (permanent switch on and off) must be avoided for a better efficiency of the system.

Proper selection of High Efficient Electric Motors

Producing high efficient electric motors increases production costs because of expensive and additional materials. If the investment costs are not important, you can always choose premium efficient motors. But if you consider paying off investment costs, you have to calculate daily working hours,price of electricity and the advantage of using premium efficient electric motor. For example if an electric motor is working for an hour weekly, it will take long time to pay off. It is not necessary to use premium efficient electric motor.

In an example:

Assume that we want to compare annual energy savings of an Eff1 and Eff2 electric motors for a pump system which has 7,5 kW power and operates 24/7. The electricity costs 0,15 TL/kWh.

Electrical input power of an Eff1 electric motor is:

Under this conditions Eff1 electric motor can save 206,9-201,1 = 5,8 kWh energy and 5,8*0,15 = 0,87 Lira in a day compared to Eff2 electric motor.With this you can save 317 TL in a year.

If this electric motor would work an hour per day, youcould save 13 TL in a year. You can buy a standard Eff2 electric motor from market with the price of 510 TL and a standard Eff3 motor with the price of 1250 TL. You have to consider these values when you are making an investment.For more information please contact ELK Motor.

Electric Motor Efficiency Classes

In 2000 the European Committee of Manufactures of Electrical Machines and Power Systems (CEMEP) issued a voluntary agreement of motor manufactures on efficiency classification with three efficiency classes: Eff1 for highest efficiency, Eff2 for standard efficiency and Eff3 for lowest efficiency.From 2004 the electric motors with Eff3 class are banned in Europe. International Standard IEC 60034-30 defined new energy efficiency classes for electric motor in 2008: IE1, IE2, IE3 and IE4.

According to this new identification:

IE1: Standard Efficiency (According to CEMEP: Eff2)

IE2: High Efficiency (According to CEMEP: Eff1)

IE3: Premium Efficiency

IE4: Super Premium Efficiency

The error tolerance limits for motor efficiency are(1-Efficiency) x 0,15. If the actual electric motor efficiency is toleratedwith ± this calculated value, it is in the specified class.Eff and IE efficiency values are approximately equal.Small differences between Eff and IE values are due to additional losses and different calculation methods.Eff additional losses were always allocated as 0.5% in the old standards, it changes between 0.5% - 2.5% in the new IE standards depending on frame size.