Super Efficient Motors:Techanical Overview

By | March 27, 2013

Abstract

Power scenario in the country calls for energy crisis management. Industrialization and growth in population is creating a void between demand and supply, and this void is deepening day by day.   The generating cost is increasing day by day & the power tariffs are on the rise. Unless the above crises are properly managed power scenario will be bleak. Conservation of the energy is the call of the day.  There is a capital investment that can repay many times its original value over the next 20 years. At the same time, it can improve equipment reliability. The investment is straightforward: install electric motors having the highest electrical energy efficiency commensurate with your needs. Energy-efficient motors pay for themselves in a few years or sometimes even a few months, after which they will continue to pile up savings worth many times their purchase cost for as long as they remain in service.


1. Introduction

Until the energy crisis in the 1970s ,most general purpose motors were designed to provide rated output and operating characteristics at reasonable cost ,period. Efficient operation was best a secondary consideration .As energy crises began rising however , manufacturers began promoting improved motors they called high efficiency and energy efficient, although the terms were not defined specifically at the time.

Old style standard efficiency motors remained popular because they generally cost less than the new models. Purchasing agents were seldom inclined to spend a little more money up front in order to save on energy cost later on. But today the story is entirely different. Looking at the power scenario in the country, there exists a huge gap between the demand and the supply which is widening. The generating cost is increasing day by day and power tariffs are on the rise. This is affecting the profitability of all the industries. Hence it is a trend in the industry to look for the opportunities of cost reduction. The major cost components in an industry include material,labour and energy costs. Material and labour cost reduction has its own limitation and a manufacturer does not have a direct control many times. But the manufacturers himself can influence the energy cost through energy conservation measurers and effective energy management


2. Motor utility segmentation

The figures of the motor purchases in 2003-04 will give an idea of this potential. About 5 million motors accounting to approximately 5 million kW have been sold in 2003-04. (These figures are as reported by IEEMA & are approximated to round figures). The non-reporting members also account for an additional 3-4 mil. KW.

Fractional HP motors account for over 85% of volume. These small motors are used primarily in domestic appliances and are lightly and/or intermittently loaded. As a result there is little potential for cost-effective energy savings. Direct current (DC) motors have applications in the industrial sector. There are few DC motors in-service and most are being phased out in favour of alternating current (AC) motors with inverter drive systems. AC low-tension (or low voltage) motors are used by all end-user segments and represent largest market, following fractional horsepower motors.


3. What does energy efficiency mean?

Electric motors are simply devices that convert electrical energy into mechanical energy. Like all electromechanical equipment, motors consume some “extra” energy in order to make the conversion. Efficiency is a measure of how much total energy a motor uses in relation to the rated power delivered to the shaft.                               A motor’s nameplate rating is based on output horsepower, which is fixed for continuous operation at full load. The amount of input power needed to produce rated horsepower will vary from motor to motor, with more-efficient motors requiring less input wattage than less-efficient models to produce the same output. Electrical energy input is measured in watts, while output is given in horsepower. One horsepower is equivalent to 746 watts.          There are several ways to express motor efficiency, but the basic concept and the numerical results are the same. For example:

Efficiency, % = 746 x Horsepower (output) x 100
Watts (input)


Efficiency, % = Watts (output) x 100
Watts (input)

The ratio describes efficiency in terms of what can be observed from outside the motor, but it doesn’t say anything about what is going on inside the motor, and it is what’s happening inside that makes one motor more or less efficient than another. For example, we can rewrite the equation as:

Efficiency, % = Watts (output) X 100
Watts (output) + Watts (Losses)

Or its equivalent,

Efficiency, % = Watts (Input) – Watts (Losses) x 100
Watts (Input)

“Losses” stands for all the energy “fees” the motor charges in order to make its electrical-to-mechanical energy conversion. Their magnitude varies from motor to motor and can even vary among motors of the same make, type and size. In general, however, standard-efficiency motors (pre-EPAct) have higher losses than motors that meet EPAct standards, while NEMA Premium motors, or better, have lower losses still.

Please Share: Tweet about this on TwitterShare on FacebookShare on Google+Share on RedditPin on PinterestShare on LinkedInDigg thisShare on StumbleUponShare on TumblrBuffer this pageShare on VKEmail this to someone

Leave a Reply

Your email address will not be published. Required fields are marked *