COST IMPLICATIONS & SAVINGS USING HIGH EFFICIENCY ELECTRIC MOTORS

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COST IMPLICATIONS & SAVINGS – It is imperative that all factors are taken into consideration when calculating the potential cost saving of standard motors versus high efficiency. Some of the factors that should be considered have been explained above as well as the following : Stock – Is the high efficiency motor range chosen by your Company a standard stock item in all voltages and sizes that are immediately available.Non-standard high efficiency motors are not held in stock unless there is a special arrangement with customer & supplier. ( This type of agreement generally binds the customer to one supplier. )

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Price variation – Generally High Efficiency 2 motors are standard stock items held by most suppliers at competitive prices.The additional cost to purchase Efficiency 1 will differ from eachsupplier but is in the region of 30% to 45% above standard prices. Dimensions – High Efficiency motor dimensions can differ from previous standard sizes. The motors will generally be longer to accommodate for larger stator cores.

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Eff Standard – Customers have to rely on suppliers published performance data in respect to purchase & calculations. South Africa do not have a proper Efficiency standard that suppliers have to conform to or have their motors tested against. In a recent independent test conducted by a large corporation it is apparent that there a definitely a concerned variation between suppliers published data & actual tested data.If no specified repair plan or procedure is in place with your approved armature winder which specifically covers the rewind or repair of a High Efficiency motor, one should then possibly spare the extra expense of purchasing a High Efficiency motor in lieu of a standard motor.Insulation class – Generally the world standard is Class F insulation. Suppliers in South Africa normally offer Class F insulation with B temp rise. Should you purchase a motor from a reputable supplier, correctly sized, applied and installed and it is operating under the conditions for which was designed you will have no reason to be concerned about overheating.

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UNDERSTANDING HIGH EFFICIENCY – A major misconception in the marketplace is that the purchase/installation of High Efficiency motors will automatically contribute to energy and cost saving. There are various ratings of High Efficiency been offered by motor suppliers from Standard Eff 3, Eff2 & Eff 1. ( Each individual company might have their own efficiency brand / name). Generally however motor suppliers will quote their particular Efficiency standard in accordance with a International recognized standard. ( CEMEP – European ; EPACT – USA ; MEPS – Australia ). It is generally accepted that a High Efficiency 2 motor with regards Efficiency, Power Factor and cost is the most economical and widely accepted standard of High Efficiency motor currently in use in the world today.The added cost implication of between 30% to 45% to increase from a Efficiency 2 to Efficiency 1 motor compared to the minimal improvement in efficiency has prevented Industry in Europe and other industrialised countries to implement Efficiency 1 motors as standard.

CONSIDERATIONS PRIOR TO CHANGING TO HIGH EFFICIENCY MOTORS MOTOR MANAGEMENT PLAN – It is imperative that a concise plan incorporating the identifying of motor loads, hours of operation, critical motors, maintenance and repair is in place, prior to uniformly replacing existing standard motors to high efficiency motors.
MOTOR LOADING – Motors operate at their highest efficiency between about 65% and 100% of their full-rated load, dropping off sharply in efficiency below 50% loading. It is generally accepted that about one-third of motors in the field are so oversized that they operate below 50% of rated load most of the time. Motors operate at their peak efficiency if they are sized correctly for the load that they will drive. Oversized motors not only operate inefficiently, but they also carry a higher first cost than correct sized units. They can also contribute to reduced power factor, which may result in increased electricity costs and poorer utilisation of the power systems.

HOURS OF OPERATION – Hours of operation is a critical factor in determining the replacement or purchase of High Efficiency motors. Motors with more operating hours use more electricity and cost more to operate. Standard motors operating above 4000 hrs / year (ie.167 days x 24 hrs/day) should be considered for future replacement with high efficiency motors.

HIGH EFFICIENCY POWER FACTOR – Power factor for High Efficiency motors are generally equal or lower than standard motors ( Eff 3 ). The lower power factor can be corrected by applying the correct power factor correction. ( One must take both Efficiency & Power factor data into consideration when purchasing a High efficiency motor)

MOTOR RANGE BEST SUITED FOR REPLACEMENT – Research has shown that smaller kilowatt motors have the best benefit & gain in motor efficiency. CEMEP high efficiency tables show the most effective range to be the following :

2 Pole – 1.1kW to 90kW

4 Pole – 1.1kW to 90kW

On larger motor efficiency the difference between Eff 3 , Eff 2 & Eff1 is small & the gain can be relatively insignificant.

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