The directive encourages users to select the most energy-efficient overall system (motor + motor starter). Depending on the application, the most efficient system might be obtained with a Variable Speed Drive, but not always…
Motors’ efficiency classes
International standard IEC 60034, which dates back to 2008, set forth four energy-efficiency classes for motors:
- IE1: standard efficiency
- IE2: high efficiency
- IE3: premium efficiency
- IE4: super premium efficiency (not yet enforced)
These classes replaced an older set of classes, which were numbered in reverse order from EFF3 to EFF1.
Targeting electric motors and electrical consumption
At the EU level, Directive 2005/32/EC established a framework for eco-design, setting forth the requirements for energy-using products. Through a series of recommendations, manufacturers are encouraged to reduce their products’ energy consumption and improve their efficiency.
Given that, in the industrial sector, electric motors account for 80% of electrical energy consumption, and electricity accounts for 40% of all energy used, Regulation EC640/2009 implements the directive for electric motors.
When will the Directive be implemented?
The Directive will be implemented according to the following calendar:
• 2011: All motors must be IE2
• 2015: Motors between 7.5 kW and 375 kW must be at least IE3, or IE2 if a variable speed drive is used
• 2017: The Directive will apply to motors between 0.75 kW and 375 kW
First, be careful not to misinterpret the Directive. Just because an IE2 motor is used with a variable speed drive does not make it as efficient as an IE3 motor with a traditional motor starter. It is the energy efficiency of the overall system that should dictate your choice between starter and variable speed drive: using a drive when a contactor would be sufficient may result in a very poor overall efficiency.
Our recommendation to select your solution:
– If the application does not require varying the speed, we recommend implementing a traditional low-energy consumption motor starter (contactor, Star Delta starter, or Softstarter) associated to an IE3 motor. Motor starters have less power losses than drives, are simple to install and use, have no Electro-Magnetic Compatibility issues and are highly reliable devices. The motor self-adjusts to the variation of the load demand by varying its torque.
– If however the application really requires varying the speed independently from the torque, a Variable Speed Drive associated to an IE2 or IE3 motor will ensure the best overall efficiency, especially compared to conventional mechanical speed limiters (dampers, valves…).
– Finally a clever association of a Variable Speed Drive and contactors (cascaded or in parallel) should be considered in case of load changes, to ensure an efficient, adaptable but not too expensive solution.
If you would like to learn more, I advise you to visit the electrical installation wiki page about Motor Energy Saving Opportunities
and also to download the brochures published by CAPIEL (European Coordinating Committee of Manufacturers of Electrical Switchgear and Controlgear)