Energy-Efficient Motors

July 18, 2005

3 Min Read
Energy-Efficient Motors

How has the role of power management electronics in motion control changed in the past five to 10 years?

I think what has happened to motor controls in the last five to 10 years is it has gone from a way to make motors to a way to save an enormous amount of energy. Fifty-one percent of all of our electricity, which is 20 percent of the global consumption of energy, goes into electric motors. More than 80 percent of those are the inefficient motors like brush dc or, more importantly, single-phase ac induction motors, which waste a lot of energy. However, those kinds of motors are easy to control. So in the good old days before the five- to 10- year [time frame] that's how we would control motors. You get a little triac and you could spin an ac induction motor pretty well. We have since learned how to very economically control motors that are much more efficient, such as three-phase ac induction permanent magnet motors.

What changed to make this happen?

The reason for all this is an architecture that IR pioneered about 10 years ago using our high-voltage ICs to actually control the three-phase ac induction motors. It lowered the cost. It also eliminated the need to use step down and pulse transformers or optoisolators in the control of the high-voltage transistors on the output. That opened up a huge set of opportunities because once you can start controlling lower horsepower motors efficiently and economically, you can start replacing [them in applications] where the vast amount of the single-phase ac induction and brush dc motors are being used. Single-phase induction motors are the mainstay of the age-old appliance industry—refrigerators, washing machines, and air-conditioning. By going to permanent magnet ac motors, you can very much reduce the energy, as a matter of fact, about 50 to 60 percent. That certainly is where IR is focused.

What other technologies are involved?

It wasn't just a matter of coming up with high- voltage ICs, it was a matter of focusing on improved generations of IGBTs, improved generation of diodes, improved control algorithms, improved digital control chips, and improved packaging. So, now we have really come to the point where we can economically control efficient motors for the cost of a belt, a gear, and a pulley.

Is one region of the world more receptive to improving energy efficiency? If so, why?

I think they all have their different flavors to it. Certainly China and India are dealing from a position of a growing middle class that can now start affording some luxuries like air-conditioning. Yet with a power grid that is not keeping up, energy efficiency is mandatory. It is being driven by the consumer desire to have an air-conditioner, a PC, and a light run at the same time in an apartment. It does not matter how much they have, they cannot do it unless they use energy-efficient light bulbs and air-conditioners.

If power electronics technology was adopted as you have described, what kind of savings could be realized?

I think there is a 30 percent overall global savings that is possible. In 2001, there were 404 quadrillion BTUs of energy used on a global scale of all forms of energy. Electric motors are 20 percent of the world's energy consumption and we can save half of that by going to efficient variable speed drives, so that's 10 percent. There is nothing else that I know of that can have that big of an impact.

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