Making Motors More Energy Efficient

For most consumers, a single glance at their monthly utility bill provides striking evidence of the need for cheaper alternative energy sources. Yet putting viable new options into widespread use in the U.S. is a formidable challenge, even though many serving in government are keenly aware of the need to develop new power sources. The road to implementing these sources may be uncertain and long.

In the meantime, there is an alternative strategy. Electric motors, such as those in our homes, consume over 25% of the electricity in the U.S. and many operate inefficiently. By dedicating ourselves to maximizing energy efficiency, we can significantly cut the costs of operating the standard electric appliances we all use as well as reducing the amount of energy they consume.

Consider the operation of the single-phase motors that are found in residential and small commercial appliances such as refrigerators, clothes washers and dryers, air conditioning units, pumps, and fans. Such motors are designed to run most efficiently at high loads, usually at least 70% of their full-rated load. Yet in real-world applications, motors often operate at less than 40% of full load for extended periods of time. Future models of these appliances could be made to run more efficiently with the use of a single-phase motor efficiency controller. In addition, existing lines of appliances can be fitted to enhance their efficiency as well.

How does an efficiency controller work? Consider a washing machine: more energy is required when the appliance is filled with many clothes and less when there are just a few items to wash. Yet most washing machines consume more electricity than they need when they are lightly loaded, wasting energy. By contrast, an efficiency controller will provide precisely the right amount of power to the washing machine to meet the demands of its motor at any given time. High-speed response circuits continuously monitor the current and voltage and adjust these accordingly, so that the motor maintains its rated speed and torque under variable loads. More specifically, when the voltage and current sine waves diverge greatly (i.e., when the phase lag increases), the motor is lightly loaded and operating inefficiently. The efficiency controller detects this and reduces the current and voltage appropriately. Conversely, when the load on the motor increases, the device registers this fact and increases the power to the motor so it doesn't stall.

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Source: Industrial Control DesignLine