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issue: March 2007 APPLIANCE Magazine

The Open Door
Getting the Most from Your Motor Dollar


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U.S. appliance manufacturers are focused more than ever on market share, production volume and profits. To that end, working engineers have to focus their efforts on designing appliance systems that add and improve functions and features that meet customer needs and command higher prices and profits.

The design focus must be a system approach. No one component needs to bear the full burden of system improvements. Motor performance or improvements are only valued if they support the goals of the system. Over-design or added performance is usually not rewarded.
Applying electric motor technology in appliance applications very much depends on the individual needs of the desired functions and features. Trends in usage gravitate toward applying motor technology that best matches the application performance requirements that, in turn, support the more profitable functions and features. For example, high-end washing machines offering convenience as well as water/energy savings have moved from brushless permanent-magnet (PM) motors and switched-reluctance (SR) devices to the tried and true (and lower cost) AC induction motors with electronic controls.
Refrigerator compressors work well within a relatively low speed range but can benefit from higher efficiency operation once up to operating speed. A hybrid device combining single-phase AC induction motor operation with the synchronous performance of a PM machine is an increasingly popular choice. An AC PM synchronous machine uses existing production infrastructure of a single-phase AC induction motor, but it adds a few magnets in the rotor to achieve higher efficiency using the magnet flux to lock into a synchronous speed once it gets going. In return, the current in the rotor is greatly reduced compared to the standard, magnet-less AC induction rotors, lowering current heating losses and, thus, achieving efficiency gains. A single-phase device, working off the line, reduces wiring that exits the sealed compressor unit, reducing the opportunity for compressor fluid leakage.
SR motors are replacing universal motors in high-speed rotation applications such as vacuum cleaners. Single-direction operation keeps SR control relatively simple, while providing brushless operation without magnets—a cost-effective combination. Higher power density is also a plus.
Low noise is an attractive attribute to any appliance. Initially, brushless PM devices were employed to achieve performance with lower noise. But as control of AC induction motors has improved, these lower cost devices are beginning to replace PM in areas such as dishwashers, air-conditioners and heating appliances.
As manufacturers consider cost, they continue to move production closer to their customers, especially in Asia and South America. Motor supply has followed. Today, many compressors and motors are manufactured in Brazil. China has, of course, received a lot of press about its significant motor production for high-volume appliances. The lower labor costs of these countries understandably makes them appealing. However, adopting a “low-cost” motor acquisition strategy may not be the only approach to meeting your electric motor needs.
Another strategy is to consider the “cost of ownership.” Cost of ownership takes into account quality and reliability (driven by automation), experienced engineering talent and superior, timely communication with your supplier. Using this strategy, mistakes can be reduced, and quality increased—all leading to a decrease in the overall cost. In fact, a few examples of U.S.-produced motors overcoming lower labor cost suppliers (and the added shipping costs), are beginning to crop up.
Also, risks resulting from purchasing in low labor cost countries are expected to increase, particularly with China. Chinese suppliers are also coming under some cost pressures as the Chinese equivalent of the EPA is beginning to recognize the environmental destruction caused by unfettered manufacturing practices. Fears of a revalued Chinese currency also have given some companies reason to begin selectively cultivating U.S. suppliers as a hedge.
Savvy appliance designers recognize the system nature of their designs and balance the cost of selecting higher performing electric motors against achieving system goals through other component improvements. Knowing the various combinations of motor design and performance and their trade-offs will increase the probability that you will get the most out of your electric motor purchasing dollar.

About the Author

George Gulalo is the co-founder and president of Motion Tech Trends (MTT), an Inglewood, California, U.S.-based consulting firm specializing in the electric motor and motion control industry. He has a BEE from New York’s City College and an MBA from the University of Southern California. If you would like to contact Gulalo, e-mail editor@appliance.com

 

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