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Here is an interesting fact, of all the electricity used in industry nearly 70% is consumed by Electric Motors.


Hopefully the above fact is reason enough to understand why there is a major focus on improving motor efficiency worldwide.

Today IE3 motors provide premium efficiency and are helping to reduce CO2 levels each year.

For improved efficiency read, less energy cost and less impact on the environment. A double win.

There are a number of ways to improve motor efficiency, for example simply ensuring you do not oversize or run continuously when not required.

But installation of motor control devices including; star-delta starters, soft starters and variable speed drives are mostly thought of when improving efficiency. 

The last example of using a variable speed drive will ultimately improve efficiency and give greater control of the motor with the added benefit of extending the life of the motor and all transmission drives and components. If you are looking to reduce energy cost, together with greater control and maintenance downtime then a VSD is something to seriously consider.

Graph illustrates that with VSD control a fan running at 80% speed uses 50% less power than with DOL starting


Another reason to look at VSD control is the next step in the ErP Directive

"By January 2017 all 2, 4 and 6 pole single speed, three-phase induction motors from 0.75kW to 375 kW rated to 1000 Volts placed on the market will need to be IE3 efficiency rated".

Let's go back a little

Since January 1st 2015 placing an IE2 motor in the range of 7.5kW - 375kW on the market has required that a variable speed drive must be fitted in order to upgrade the motor to an IE3 efficiency rating.

Prior to this the efficiency requirement in 2011 changed to IE2 for the range of 0.75kW - 375kW,

Move forward a little

In January 2017 the efficiency for the 0.75kW - 375kW range will be IE3, thus closing the gap in the 0.75kW - 7.5kW range. Again any IE2 motor placed on the market from January 2017 must have a variable speed drive fitted in order to make the IE3 efficiency rating.

Wouldn't it be easier to simply exchange an IE2 for an IE3 motor?

Sometimes the cost of doing so may be more expensive than installing a VSD to an exisiting system fitted with IE2 motors. However if you are using IE3 motors fitting a VSD is still a strong recommendation. Regardless of whether IE2 or IE3 are installed, VSD's in combination ultimately lead to greater energy savings, improved motor control and less maintenance cost due to less stress and loading of the drive train and components.

What you may also need to consider 

Higher efficiency motors have higher inductance due to reduced copper losses, this means the motor starting currents would be higher (you can install motor control to reduce starting currents), so it's import to ensure the switchgear such as; contactors, circuit breakers and the like are capable of handling the increase, if not these may need to be changed. 


For drives and switchgear check supplier links below







Favourite things are Family, Music and Judo. Also, I have the ability to retain and quote useless facts, something that pleases me but can annoy others. My engineering hero - Isambard Kingdom Brunel