TechArchive

Original article date: October 1999

Guidelines as to what constitutes a motor that can be used in the USA for general purposes – and is therefore covered by EPACT – have been clarified. The clarifications have come from NEMA and the Department of Energy which has the official responsibility for rulemaking and enforcement of EPACT mandates. Stephen Horsfall Managing Director of Motovario UK (formerly Gorton Engineering Products) is your guide

Today is an exciting – and challenging – time for specifiers buyers users and manufacturers of industrial electric motors for use in the USA and North American markets.

The industry is experiencing a time of great change rivalled only by the introduction of re-rated T frame motors in the 1960′s.

But there is a difference between that change and this one. The T frame evolution was perpetuated by the motor industry itself. Driven by economics and market force realities.

Today however we have seen a government mandate. As the law of the land most industrial motors produced after October 24 1997 were required to operate at the mandated efficiency levels prescribed by the Energy Policy Act of 1992.

These legislated efficiencies are not challenging from a design or manufacturing point of view. In fact mandated efficiency levels are generally lower than the premium efficiency motors which have been available from major manufacturers for many years.

The major change of EPACT has been felt in the increased cost to motor users as mandated efficiency Design B motors became the new standard used in many industrial applications and also as components in a wide variety of industrial machinery.

In addition many motor users have found that National Electrical Manufacturers’ Association (NEMA) Design C torque motors – which are not covered by EPACT mandates – are excellent choices for many applications where a bit more torque is desirable.

And their standard efficiencies may be perfectly adequate when balanced against actual duty cycle – or the lower up-front cost.

Guidelines as to what constitutes a motor that can be used for general purposes – and is therefore covered by EPACT – have been clarified. The clarifications have come from NEMA and the Department of Energy which has the official responsibility for rulemaking and enforcement of EPACT mandates.

The specialist power transmission services of Motovario Ltd. formerly Gorton Engineering are suddenly growing in demand because of the need for NEMA motors to meet the latest EPACT mandates.

Motovario has found that many UK exporters of machinery are not aware of the EPACT directive which has the implication of a heavy fine of up to $100 dollars a motor.

Motovario has a range of Leeson motors which can competitively fulfil the EPACT specification requirements. Their range is from sub-fractional to 1000 hp and includes 3 phase 1 phase brake and explosion proof versions a metric series and dc.

They can also supply compatible gear units with NEMA motor flanges and imperial shaft dimensions.

Driven most recently by the EPACT legislation motor efficiency has today become an imperative.

In a nutshell this is what the law means to the industrial motor user whether the motor is for replacement use on existing applications or is a component of another machine.

Three phase general purpose NEMA T frame motors of 1-200 hp manufacturered after October 24 1997 must meet government mandated efficiency levels.

These EPACT levels are higher than those of most manufaturers’ previous standard efficiency motors but generally not higher than many manufacturers’ long-standing premium efficiency lines.

In that sense motors of the new efficiencies are not really all that new at all. The real difference is in how much more widespread their manufacture availability and requirement became as of late 1997.

Electric motors have a huge impact on overall energy usage. Between 30%- 40% of all fossil fuels burned in the world are used to generate electricity and a large proportion of that electricity goes to run motors.

Nearly all estimates say that at least 60% of electricity in the United States is used to power motors. Given the overwhelming number of small motors in consumer use well over half of motor power demand falls to this (for now) unregulated motor segment.

But that still leaves a sizeable power demand within the industrial motor population. At current electric rates perhaps $30 billion worth of electrical power per year.

This means that within the overall industrial motor segment every percentage point gain in overall motor efficiency translates into $300 million of yearly savings.

Maximising industrial electric motor efficiency is clearly important. This is true in public energy policy terms as well as environmentally in reducing greenhouse gases associated with fossil fuel burning. Plus it is also good business practice.

Three phase 1 hp general purpose T frame…those are the key elements to remember about which motors will – or will not – be covered by the EPACT guidelines.

The specifics are:

Any non-exempt motor manufactured after October 24 1997 must meet the EPACT efficiency levels as administered by the Department of Energy and related agencies. These levels are the same as those listed in the MG-1-1993 standards published by NEMA.

The law clearly does not require any motor user to replace an existing motor with a higher efficiency model (though in some applications you might want to do so for economic reasons based on energy money saved).

And because motor companies are manufacturing motors – and filling inventory channels all the time – there will certainly be standard motors in the pipeline for months and probably even years to come.

Customers may buy and install these pre-EPACT manufactured motors (presumably at a lower price than the newer high efficiency models) as long as they are available.

Similarly the law makes no reference to used or rewound motors. Those may be bought at will regardless of efficiency though over time it is likely that the market place will demand a proven if not certified level of efficiency from rewound or otherwise reworked motors as well.

Whilst the scope of EPACT is certainly widespread covering perhaps half of all industrial motors the mandate does not address all types of motors. Its focus is on small to medium horsepower ac motors used in general industrial applications.

It states only 3 phase 230/460 VAC motors from 1-200 hp. Furthermore these must be general purpose T frame motors with three digit frame numbers NEMA Design A or B rated for continuous duty. Open and enclosed motors are included as are two pole four pole and six pole designs (3600 1800 and 1200 rpm).

Imported motors as well as those manufactured in the United States are covered (hence the increase in Motovario’s specialist services). These motors can be sold for replacement applications or incorporated into other machinery.

Motors requiring third party approvals such as explosion proof designs are to come under the law’s scope in October 1999 The law specifically applies to horizontal foot mounted motors including foot mounted motors which also have a NEMA C face mounting.

Definite purpose or special purpose motors are exempt. The law defines definite purpose motors as those which cannot be used in most general purpose applications.

The law defines special purpose motors as other than general purpose or definite purpose motors which have special operating characteristics or special mechanical consideration designed for a particular application.

High slip (NEMA Design D) or high torque (NEMA Design C) motors are examples of special purpose motors under this definition. Other examples are multi-speed or low rpm motors and those designed for special voltages.

In addition single phase motors are exempt as are any motors built in double digit frames (42 48 and 56 which are defined as fractional horsepower frames). It is not uncommon to find motors of up to 3 hp built in NEMA 56 frames. Even though they are clearly 1 hp or greater these are exempt.

In reality the whole issue of how much – or how little – single phase or fractional horsepower motors are affected revolves around setting standards for what the law generically refers to as small motors meaning under 1 hp any motors in two digit NEMA frame sizes or sub fractional motors.

The law does not differentiate between single phase and 3 phase and 3 phase small motors but the greatest population of fractional and sub fractional motors are in fact single phase.

EPACT requires the Department of Energy to adopt standards for most small motors to be effective by October 24 2001 Subsequent legislation has made this deadline unlikely. There are other issues peculiar to single phase motors that must also be resolved.

These includes what types of single phase motors are covered how the term general purpose applies what efficiencies will be mandated and what test method will be used.

Because there are many types of single phase motors would there have to be differing standards for each type? IEEE 114 the standard that prescribes single phase motor test procedures was inactivated in 1992.

More fundamentally would inheritently inefficient designs such as the inexpensive shaded pole motors often used in consumer appliances be exempt from regulation or at the other extreme possibly even prohibited either by direct legislation or as part of requirements for overall appliance efficiency?

In many cases however small motors on appliances may already be affected within the scope of overall appliance efficiency requirements. However it all shakes out it seems plausible that if nothing else logistical problems will likely keep single phase motors out from under the EPACT umbrella for some time to come.

At the other extreme will motors larger than 200 hp come under the scrutiny of the Department of Energy? It is possible at least from 250-500 hp in low voltage because NEMA has already established efficiency values in this range.

Larger than 500 hp – especially in medium voltage 2300 VAC – it seems very unlikely for at least three reasons.

Firstly there is a relatively small population of these motors. Secondly and most importantly the enormous energy demands of these large motors have already driven buyers and manufacturers alike towards higher efficiencies.

Thirdly with motors above 1000 hp few truly standard general purpose types exist…they are almost always application specific.

Finally EPACT gives the Secretary of Energy the option of excluding other motors for which standards setting would not be feasible or those where the energy savings would not be significant.

There had been concern that EPACT by mandating general purpose motor efficiencies would limit the motor buyer’s options and take economics out of the buying equation.

In fact by increasing the range of efficiency choices EPACT has expanded the possibilities. Buyers can choose from EPACT efficiency motors or perhaps premium efficiency NEMA Design B motors exceeding EPACT mandates.

On the other hand higher torque NEMA Design C motors which are exempt from EPACT mandates may provide a lower cost alternative for applications requiring four pole or six pole speeds. And some standard efficiency motors manufactured before the EPACT deadline continue to be available for sale from suppliers’ stocks.

The key factors in any energy saving equation may be the number of hours the motor is run – and at what load. If it runs a lot at nearly full load chances are the balance will tip towards higher efficiency. At the extreme the savings may be so great as to warrant taking a perfectly serviceable older motor off line and upgrading to a new higher efficiency one. If the usage is less continuous or at lower loads it’s unlikely that upgrading a working motor will make sense.

Other application considerations also come into play. For example on some direct drive centrifugal applications such as a fan or pump the somewhat higher operating rpm common on higher efficiency motors can drive up the load and output enough to offset the energy savings.

On centrifugal loads the horsepower needed increases by the cube of the speed so a small increase in speed will have a correspondingly greater impact on load.

Higher rpm could also increase overall operating efficiency by allowing a piece of machinery to finish its job more quickly. As always the results will vary with the application. Some designs that concentrate only on efficiency can exhibit unusual characteristics. One example is high locked rotor amps which could affect wiring and starters especially in the next generation of motor efficiency.

Finally the durability of high efficiency motors. In general it should be enhanced compared with standard efficiency designs because of improved materials less heat generated and a somewhat larger core size which will tend to fend off the extra heat stress of peak loads or start/stop operation.

Still this durability difference could be difficult to measure given the reliability and long life of virtually all industrial duty ac polyphase motors. The best statement might be this: rest assured that high efficiency motors like their standard efficiency counterparts will be among the most reliable pieces of industrial machinery you’ll ever own.

The above is an extract from a booklet which is available through Motovario Ltd. For a copy of the booklet contact Sharon Dickinson Motovario Ltd. Rushock Trading Estate Droitwich Road Rushock Worcs. WR9 ONT. Tel: 01299 250859.

October 1999