Power Transmission
Is EISA a solution in disguise?
Robin Cowley outlines the main considerations that many machinery OEMs need to review for future exports to North America in the light of the EISA regulations.
I
n the run up to the introduction of the USA’s Energy Independence and Security Act) (EISA) regulations in December 2010 - which have been echoed in Canada in January - my company received many calls from machinery OEMs, to see if their particular equipment is
going to be affected, and to discuss replacement motors. A few were shocked to find that upgrading to EISA-
grade efficiency - which must meet NEMA Premium ratings (equivalent to IEC ‘IE3’ efficiency in the EU) might require some considerable engineering effort. There is not room here to detail all of EISA’s
requirements, but in summary it’s much broader in scope than the USA’s previous EPact efficiency law, which covered general purpose motors up to 200 HP. EISA now covers new motors from 1 to 500 HP. Baldor publishes a useful FAQ primer on what EISA is - details below. To ensure a smooth transition to higher efficiency, an
understanding of the mechanical and performance differences of these motors is essential in order to realise maximum financial benefits and a trouble-free installation. Energy savings are not the only benefits to premium efficient motors, many other benefits are apparent to the end user. Transitioning considerations apply to the following main
areas:
Mechanical differences. Higher efficiency motors can be larger physically due to the extra material, particularly at the low end of the power range. They will have a smaller fan due to the cooler operating temperatures and therefore
reduced acoustic noise levels. Overall a premium efficient motor will operate cooler internally with better steel, quieter, less mechanical stresses through tighter fits and better balancing. This will result in providing a more reliable, longer life-cycle motor installation. Improved productivity from less down time is an additional benefit to a change out to higher efficiency motors.
Electrical power requirements. Using a premium efficient motor will reduce the full load current drawn from the power supply. Therefore the electrical protection of the motor must be reviewed. Conversely, the starting current (or inrush current) will usually increase from 4-5 times full load for a normal efficiency motor, to 6-8 times full load for premium efficient motors. Therefore, the motor overload protection system will also need to be reviewed.
Installation and application. Checking the motor for oversizing is always recommended as changing to high efficiency offers the chance to optimize motor size. Higher efficiency motors operate at higher RPM for the same load and this can cause problems with the driven load, particularly fans, pumps and other quadratic type loads. Starting torque on higher efficiency motors can be less, therefore a check is needed against the characteristics of the driven load. Under loading the motor does not improve efficiency. This may have been true with older, less efficient designs, but higher efficient motors will typically have the best power factor and efficiency at near full load.
Fig. 1. Some of the key construction features of premium efficient motors. 46
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