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Importance of Premium Efficiency Motors
Motion control, servos, steppers, etc. topic
Posted by Rich G on 19 June, 2002 - 12:51 pm
Just how important is a premium effecient motor/drive in the real world?

Our company is looking at a promotion on the topic of energy conservation at the industrial level. In my non-scientific poll of customers (mainly OEM) there seems to be little or no concern and would lean towards whatever is the cheapest (which is the standard efficient class). My question would be: Is a premium effecient motor/drive worth the extra dollars to you and are you at a plant level or an OEM machine providor.


Posted by Bruce Durdle on 19 June, 2002 - 12:55 pm
What are you driving with the motor? If you have a standard type centrifugal pump, the motor accounts for only a very small part of the total losses between power lines and the end result (fluid movement). The variation in pump and pipeline losses due eg to wear or fouling will be
much more than the slight reduction in losses obtained using a high-efficiency motor.

Looks like the bean counters have another stick to beat us with!

Bruce


Posted by Bouchard, James \[CPCCA\] on 21 June, 2002 - 11:45 am
As an end user who is serious about energy conservation I will give you my thoughts on this matter.

1 OEM's don't care about energy efficiency unless their customer requires it. Yes they will use the least expensive motor regardless of its efficiency
if left to their own devices. You can't really blame they. You get what you pay for!

2 Even if the efficiency gains from a Premium Efficiency motor versus a High Efficiency are smaller than the gains to be made by choosing a more efficient pump or fan and keeping it in good operating condition that is no reason to ignore these savings.

3 We ( Johnson & Johnson Montreal ) require Premium Efficiency motors for most applications because there are real savings that pay for the extra motor costs within 1 to 2 years ( We pay about $026 US per KWh ) when they are running 8000 hours per year.

4 We also require performance data on fans and pumps and choose the most cost effective. In the past 3 years we have paid more for some fans because they are more efficient and we will get our money back within a few years.

5 In our case there is no payback to replacing existing motors unless they have failed and would need to be replaced anyway. Also motors that only run part time may not be economic candidates for Premium Efficiency motors.

So in summary it is not another stick from the bean counters but just good engineering practice to work out the numbers and do what makes economic
sense.

Sorry if this sounds like a rant but energy conservation is part of my job!

For more information see the DOE site
"http://www.oit.doe.gov/bestpractices/motors/":http://www .oit.doe.gov/bestpractices/motors/

James Bouchard


Posted by Bruce Durdle on 24 June, 2002 - 11:27 am
James,

I agree that use of premium efficiency motors is to be recommended. I was making the point that an energy conservation program must consider the
complete system, and the energy savings from an investment of $x are likely to be much greater if attention is focussed on the driven system
rather than the driver. But regular maintenance does not seem to be regarded favourably by the current crop of management theorists. On the
other hand, a well-publicised campaign to replace old motors with "high-efficiency" ones can earn a lot of brownie points (or should they be "greenie" points?).

It appears that we in New Zealand are about to have this legislated for us. Perhaps I'm getting old and cynical - but it seems to me that a lot of environmental initiatives are conceived so that something is seen to be done, rather than for their overall effectiveness.

Cheers,

Bruce.


Posted by Pierre Desrochers on 19 June, 2002 - 12:54 pm
When I was in charge of a foundry, and when the greens where making a pretty good lobby to stop the building of energy producing systems (mainly hydroelectric dams) the promotion of those "better" motors was high, to the point where our goverment would absorbe the stocking cost of those motors.

We did purchase many of them, only to see that we needed to maintain what was coming IN and what was going OUT of there systems (air pipes, water
pipes, dust, etc) a lot more, to gain the few percent efficency needed to have a good ROI.

What did make us purchase a few of them was there better construction, better tolerance, bearings, fans, etc. Not the fact that they have, say 93%
efficency instead of 88% !!!

To much work for to less rewards.


Posted by Bob Peterson on 19 June, 2002 - 5:26 pm
Many applications have motors that run for only a few hours a day. It is difficult to justify the extra money, as an energy saving thing anyway, in
those cases.

My concern is that my anecdotal evidence is that the more energy efficient motors are also somewhat less reliable. Motor manufacturers will tell you that premium efficiency motors should last longer because they run cooler. That may be so, but I would ask the guys that have to keep the machines running. They are the ones that really know. And the standard motors are pretty efficient already.

Another, and usually untouched on issue, is that motors are typically oversized. In many applications it is very difficult to determine just how much HP you will really need, so the tendency is to go to the next size if it is close. This, of course, results in a motor running in a much less efficient zone. Sometimes it is practical to put VFDs on motors to match the motor HP used to the actual load, but this is not always a practical option.

In the real world, this issue is driven as much by politics (both internal and governmental) as anything else. If a company wants to appear more
environmentally friendly, they may issue some kind of directive requiring the use of more energy efficient motors. I suspect that the energy savings from such directives probably does not justify the extra cost of the more efficient motors (both initial cost and additional costs due to less reliability). The reliability factor alone might make it a net loser economically.

The energy savings in using a more energy efficient motor is usually only a few percent. Run the numbers yourself and see how many decades it takes to get your extra capital cost back. Most of the time its probably going to end up not being worth it for smaller motors. The numbers tend to become more favorable as the motor HP size increases.

Look at it this way. A 10 HP motor running 24/7 fully loaded will use about 70,000 kW-hours of electricity per year. @ 3 cents/ kW-hr, thats only about $2000/year. Each one percent energy savings thus translates into about $20/year savings. And very few motors run 24/7. Most run less then 25% of the time, and rarely at full load.

OTOH, if the CEO can get himself some favorable publicity for being greener, then he may decide thats worth it to him from an ego standpoint.

Bob Peterson


Posted by Bouchard, James \[CPCCA\] on 21 June, 2002 - 2:39 pm
We have been using high efficiency motors for 20 years now and they are more reliable that the ones we were using before. The Premium efficiency motors have not shown any signs of being less reliable. Reliability comes much more from good design and proper maintenance.

The difference between standard efficiency and premium efficiency is more like 5 percentage points in 10 hp motors and 3 in 100 hp ones not
1percentage point.

You also have to figure in the demand charge which is quite a bit more ( $6.70 per kW demand ) and you pay it every month regardless of how long you use the motor. So you cannot just use the average yearly rate.

James Bouchard


Posted by T. Connolly on 20 June, 2002 - 7:01 am
Look at it from a sensible business point of veiw. A Good rule of thumb: If your buying a new motor buy a premium effecient. The ROI on the price difference is accecptable. But don't run out and blow your money to replace existing good motors, you'll never recoupe the costs, you'll do far better business wise just putting that moeny in a standard low interest savings account than replacing all your motors. In our society's rush to be energy efficient we aren't always big picture resource efficient. It will take more energy to make/ship/install the replacement motors than can be saved in the motor's lifetime. Anyone promoting replacement is really capitalizing on our conservation naivety to sell motors, not save energy.


Posted by David W Spitzer on 21 June, 2002 - 2:37 pm
Rich,

Regarding your non-scientific poll of (mainly OEM) customers --- of course they lean to the cheapest motor...they don't pay the electric bills and the cheapest motor maximizes their profit.

Others have responded regarding some of the benefits and pitfalls of energy-efficient motors. In my opinion, the economic benefit can be calculated (based upon loading, hours of operation...), so a business decision can be made as to whether to purchase a standard or energy-efficient motor in a given application.

Regards,

David W Spitzer
845.623.1830


Posted by Cameron Anderson on 27 June, 2002 - 5:56 am
Too much info has been said already, I just want to say that Baldor and Control Techniques have software packages that can show your energy savings and ROI. Like others said, AC motors have not changed much over the years, maybe gained a few points on efficiency, but that is about all.

Some one said, "OEM's don't care about energy efficiency unless their customer requires it." I would disagree with that point and go along with what you stated, "Our company is looking at a promotion on the topic of energy conservation at the industrial level." I have had customer request to put brushless servos on a system that AC motors should of done. The reason behind it is marketing wanted to put the word "SERVO" on the product literature. Other things to consider are some of the energy savings programs where the electric co. or gov't might pay for some or all of the products to conserve electricity. I am by far not an expert w/ AC drives and motor since I only deal w/ motion control (Servo, Steppers, Precision products, etc, AC drives are NOT motion control!).

Call your local Baldor or Control Techniques rep and ask them about their energy savings software and to calculate how much money a drive or new motor will save you and the time it will pay for itself.

Cameron Anderson
Motion Control Specialist
St. Paul, MN

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