We did a study a while back (among maintenance and reliability professionals) about purchasing factors for electric motors.

Reliability was super high on everyone's priority list and energy efficiency was much lower.

As energy costs are skyrocketing - has the emphasis changed at your plant or facility?

If you have made the shift to energy efficient motors, has reliability increased, decreased or stayed the same?

Terry O

In the US, the EPACT increased the minimum efficiency of motors that you can buy new. Therefore we are all buying motors with higher minimum efficiency than before EPACT.

At my plant we don’t often take the time to examine alternatives for higher “premium efficiency” motors. Doubtless we could save some money in the long term by investing mor up front, but reliability remains by far the biggest focus of our attention and efficiency is rarely examined.

Maybe it's worth to mention that my industry is the power industry. Therefore increasing energy prices translate to higher value of our plant's electrical output and generally push us to focus even more on reliability.

Another note is that newer higher efficiency motors can have different starting characteristics which can cause the new motor to trip if instantaneous trip settings are not adjusted.

How do you know one type of motor is more reliable than the other? OEMs don't put a reliability figure, do they? I only heard some recent motors are highly efficient but not robust, cannot withstand dusty & dirty environment and only fit for clean atmosphere.

EPACT stands for Energy Policy Act 2005? Which part specifies the new motor's minimum efficiency for buy?

I agree with Josh, how do u determine a motor is reliable at the time of purchasing it. A motor found reliable for a certain application may not be equally reliable for a different type of application.

I'm not saying reliability and efficiency is an either/or choice in motor selection. I'm saying we have a limited amount of attention to devote to specifying motors and we put attention on those features we feel necessary to ensure reliability.

One good collection of specifications for a "hearty" reliable motor is IEEE841. You will pay extra for it and may get some extra features you don't need, but it's a good collection of features to ensure high reliability. Things like IMPRO bearing seals, lower vib limits, 3.5 pu surge requirement, Class F insulation with Class B rise, extra testing requirements including bearing housing temperature limit etc. Special requirements for foot flatness.

If not IEEE841, be careful to specify the degreee of ingress protection for outdoor motors. Pay attention to things like space heaters. Cast iron frame.

One pet requirement of mine is to specify that 2-pole motors be tested on a RIGID base. For NEMA frame motors, NEMA MG-1 allows the manufacturer to choose either a rigid ore resilient base and further allows a slightly higher limit on resilient base (0.15ips on resilient base vs 0.12 ips on rigid base). Most manufacturers will test on resilient base (sometimes just rubber pads) because it is easier. The problem is some 2-pole motors won't show foot problems until you bolt them down on a rigid base. You will save a ton of heartache if you make the manufacturer be the first one to bolt down your motor and check the vib, rather that being the guinea pig yourself. Also observe the test if possible. (We are lucky to have a motor manufacturer within driving distance so we can do it pretty easily).

Avoid open motors (prefer TEFC). Although for large motors you generally have no choice.

Another pet requirement of mine for large (above NEMA) outdoor motors is that they should be true global VPI windings, with all materials designed for a VPI system (materials that aren't designed to absorb resin such as hybrid coil with resin rich slot section are not accepted). Also I tend to like epoxy better than polyester resin but I haven't got the nerve to add that to my spec yet since I don't have enough backup. The insulation treatment of a large outdoor motor is critical. We find much lower reliability on our original large outdoor motors with resin rich insulation systems (hard-coil / B-stage) than any of our other large motors in the plant. I'm pretty sure this is due to the insualtion system not withstanding the environment well and the industry literature seems to back that up to a certain extent. Sealed windings are another option. One nearby plant even specifies NEMA submergence test for outdoor motors but I would be nervous about that.

Ask them to put the number of rotor bars and stator slots on a labelplate on the motor. It's an extremely easy/cheap option and handy info to have.

This message has been edited. Last edited by: electricpete,

quote:

Originally posted by Josh:
EPACT stands for Energy Policy Act 2005? Which part specifies the new motor's minimum efficiency for buy?

Motor manufacturers will offer a variety of motors. Some will be identified as premium efficiency. Some will be identified as standard or Epact efficiency.

The EPACT mandated higher minimum efficiencies. You can no longer buy anything lower than that mandated minimum efficiency in the US (manufacturers can't offer anything less than that minimum efficiency).

So my point was, even if you don't specify anything, you are getting a higher efficiency motor today then you would have gotten on a standard motor 20 years ago.

Good afternoon everyone:

The Act was EPAct 1992 which mandated that motor manufacturers produce only energy efficient motors, per the industry's NEMA MG-1 tables, starting October 24, 2997. The motors in question are NEMA, T-Frame, Standard foot mounted motors, 1200, 1800, 3600 RPM, from 1 to 500 horsepower. Special motors (ie: automotive U-Frame, close-coupled pump motors, etc.) do not require such a change. The motors must meet this nominal efficiency (average) through the use of IEEE Std 112 method B.

As far as reliability: There are variations from manufacturer to manufacturer. However, to meet the standard in the first place, you have to improve the engineering and materials. For instance, two of the major losses are stator losses and friction. To reduce both of those, you have to use higher grade core steels and better classes of bearings. They are NOT more sensitive to dust, etc., they DO NOT have extremely tight air gaps, etc. They DO hold up to repair far better than their standard efficient T-Frame and U-frame machines.

In the 1990's, Premium Efficiency was not covered by NEMA, so everyone produced motors and anything above the minimum high efficiency rating suddenly became 'premium.' So, at the end of the decade, the concern of premium efficiency was addressed, primarily from pressure from the Consortium of Energy Efficiency who set their own levels and published them. Premium efficient motors have even better engineering and materials and so command a slightly higher price.

For additional information on this subject, you may wish to go to http://www.eere.doe.gov/industry/ and go through the information on electric motors. Additionally, one of the FREE tools that are available to you is MotorMaster Plus, which can be used to compare motors for retrofit, repair versus replace, etc. As one of the qualified MotorMaster Professionals, I have put together a short tutorial on the software on ReliabilityWeb as an iPresentation (http://www.reliabilityweb.com/forms/tsol_reg.htm). Step by Step instructions on the use of the software can also be downloaded for free from http://www.motordiagnostics.com/presentations.htm.

Sincerely,
Howard

To Continue

IEEE 841 was developed for the Petroleum and Chemical industry and has very specific requirements for efficiency, foot flatness, materials, etc. etc. They are excellent for high reliability applications and applications where the operating environment is severe. Paper and automotive manufacturers are also adopting this standard pretty quickly (as will be demonstrated in September's Uptime Magazine article: "The Energy Efficiency Myth: When Motor Retrofits Go Wrong" - or a variation of this title).

I hope that this all helps.

Sincerely,
Howard

Oh, in the meantime, should you decide to investigate MotorMaster Plus, here is that document on how to use it (step by step guide) including the industry-funded modifications for the DOE by Dreisilker Electric Motors, Pruftechnik and BJM Corp/ALL-TEST Pro:

MMPlus_Instructions.pdf (492 Kb, 38 downloads)

[QUOTE]Originally posted by MotorDoc:
The Act was EPAct 1992 which mandated that motor manufacturers produce only energy efficient motors, per the industry's NEMA MG-1 tables, starting October 24, 2997. [QUOTE]

MotorDoc, 2997 or 1997? Typo error?

Too much info, what is the minimum motor efficiency for manufacture now as per EPAct?

Is there any article reviewing or summarizing requirements contained in IEEE 841 for the Petroluem & Chemical Industry? Why are they excellent for high reliability applications?

October 24, 1997. Darned keys are too close.

See attached.

Yes, go to the US DOE links shown above.

As mentioned, the IEEE 841 motor requires labyrinth seals, tight vibration tolerances, foot flatness, etc. etc. Basically a high/premium efficient motor with severe duty characteristics.

Sincerely,
Howard

savings-chart.xls (178 Kb, 23 downloads)

Ok, now I see it, you are saying NEMA motors are more energy efficient than EPAct and Pre-EPAct motors.

This message has been edited. Last edited by: Josh,

Can the MotorPlus be interfaced with existing CMMS rather than a stand alone software eg to share the same master data for motors and to assess energy savings versus motor reliability?

This message has been edited. Last edited by: Josh,

quote:

Originally posted by Josh:
Ok, now I see it, you are saying NEMA motors are more energy efficient than EPAct and Pre-EPAct motors.

You're right.

NEMA premium efficiency is a higher efficiency standard than EPACT.

EPACT set a minimum efficiency that was not around pre-EPACT and is higher than many pre-EPACT motors. EPACT is now the minimum you can buy today.

http://www.nema.org/gov/energy/efficiency/premium/

Josh:

EPAct references the NEMA energy efficiency tables for minimum efficiency. After some market-related issues and pressure from energy groups and utilities, NEMA also established a minimum premium efficiency table so that there was a distinction between Energy Efficient and Premium Efficient.

MotorMaster Plus can import motor information and other tables. It is not ready to directly connect to other CMMS systems, and may not be, at least through US DOE funding, at this point.

Howard