There is a significant global effort underway to reduce energy consumption in industry by improving energy efficiency, specifically the efficiency of electric motor systems.
The initial focus was on the efficiency of individual elements, e.g. the motor, which resulted in the IE efficiency classes for motors - IE2, IE3 etc. It is now understood that greater efficiency gains are available by considering the wider motor driven system.
In Europe, Regulation EC 640/2009 is in force, requiring specific types of motors from 0.75 kW to 375 kW to meet certain IE classes. (Additional motor types and sizes are considered by a new regulation presently in development.)
There is often confusion about what the European legislation requires.
The best advice is to use a soft starter unless these is a specific need for variable speed control. Most industrial motors are used in fixed speed applications, where soft start is the most efficient electronic motor control solution – it is effectively 100% efficient when bypassed.
There is a lot of talk about using variable speed drives to save great amounts of energy. Drives may provide energy savings in variable speed applications, but if used in fixed speed applications drives will increase energy usage and running cost due to their inherent losses. They are also the most expensive choice across motor sizes from 7.5 kW to 700 kW:
It is essential to evaluate each motor driven system to find the best motor control solution. A correctly specified motor control solution can reduce your energy usage and ongoing operating expenditure; a poorly specified solution will cost you money.
The legislation intends to improve the overall energy efficiency of motor systems. Eventually IE3 will be the minimum motor efficiency class permitted.
To help with the transition to IE3, for a time IE2 motors are allowed provided a variable speed drive is used, but this is only suitable for variable speed applications. (This option assists motor manufacturers to migrate their production to IE3 motors.)
An IE3 motor with a soft starter is the most efficient solution for fixed speed applications.
Whatever the motor control method, for greater energy savings over the lifetime of your system use an IE3 motor instead of an IE2 motor.