Three-phase squirrel-cage AC induction motors are the workhorses for the industrial market. However, their development is reaching the limits of physics for efficiency.
A new technology must be adopted to reach the next levels, and this could be permanent magnet motors using some type of rare-earth magnets in the rotor, switched reluctance, synchronous reluctance, or some new technology yet to be identified. Most of these new technologies offer power density improvements over standard induction motors. But most require some form of adjustable speed drive for their operation, which can further aid in energy savings.
At this time, these new technologies are available from motor manufacturers, but have yet to become available through distribution as standard drop-in replacements for existing NEMA or IEC motor designs. Both NEMA and IEC have yet to complete standards for these new technologies, and only CSA has developed an approved test method.
John, Possibly I am making an excessive generalization, but a lot of that6 type of decisions comes from those with an MBA degree, emphasis on accounting. I am aware that we do need to keep track of money, but cost cutting should not trum doing the job right. Of course, it is the responsibility of engineers to assure that the best choices for both quality and price are made. But those decisions do need to be made by engineers, not money shufflers and bean counters.
John, you are certainly correct that system operation costs are the valid basis for comparison. BUT I have seen managers select the higher priced less efficient option simply because the short term price was less. This is in spite of seeing the actual information that proved that the more expensive selection was a lot cheaper to run. That demonstrates the quality of management in that particular branch of Delphi. That manager was the one with the realloy bad case of "toilete mouth". With that clue many should find it simple to guess his name.
We all get the idea swapping out a motor is simple. Taking an older motor out of service that still operates and replacing it with a premium efficient motor will result in a payback of 3.5 - 4 years. So that switch usually takes place only when the motor fails.
We worked with two OEMs in the past bidding on the same job. Once the order was released, one thought we gave their competitor a lower price. In fact, that was the case because the competitor's pump only required 400 HP to provide the required flow rates, not the 600 HP that the other OEM needed with his pump. So the pump may have cost a bit more for a better design, but the operating cost was a lot lower over the average of 28 years that motors live.
System analysis is the lowest cost way to save on energy.
John, the reasons for putting in a more efficient motor are a few. Improvement has to start someplace and the motor is often the simplest place. In addition, the engineer or other person responsible may not have the resources to effect any other portions of the machine. There may simply not be enough time to do anything else. Some crews can replace a motor during a shift change and have no production delays.
So we come full circle to ask the question - why put a 96+% efficient motor on a load that is 50% efficient? System efficiency has a faster payback and more savings that upgrading to expensive rare earth motors.
Even the DOE has finally recognized this in their rule making.
All induction motors do have a limit on the maximum efficiency that they can possiblyt deliver, since all of them depend on transformer action producing current in the rotating windings, and then depend on thyat current to produce the required magnetic field. So motors with permanent magnets have the possibility of being a bit more efficient. Of course there are a whole lot of other things that get in the way of the highest efficiency, so all types of motors have some limits. So it will be quite interesting to see just what type does evolve as the most efficient.
The story on electric motors is still very good. As has been detailed in Design News before, there are issues with rate earth elements, mostly on the supply side. This is an artificial problem brought on by environmental regulatons in the West and efforts by China to control supply.
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