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Using Permanent Magnet Motors In Variable Speed Appliances
Look around your house and you are likely to find a large number of electric motors. There is probably one in every appliance, from the hand mixers in the kitchen to the lawn mower fixing up the front yard. These days, electric motors are found in just about every room of the house.
There are three commercially available electric motors. The most common is the Universal, or Brush, motor. With high torque and variable speed, they work well for vacuum cleaners or drills. Induction motors have no brushes and run silently. They are single-speed and very durable and are used in pumps or refrigerators; anywhere you need constant pressure. The new motors on the market have all of these qualities: they operate at variable speeds, have high torque and they are silent and reliable.
Micro controllers have long been used for the interface functions of modern appliances. They are just now beginning to be used to control the motors themselves. The advantages in energy savings, silent operation and simplicity are becoming more and more important as technology advances and our ecological needs increase.
In applications such as drills, vacuum cleaners, mowers and even the Poulan chainsaw, variable speed is the key. Controlling the speed can increase power efficiency by as much as 30 percent compared to fixed-speed units. Designers can also use smaller, less-expensive motors, lowering the overall price.
Washing machines use a variable speed motor to lower the amount of water and electricity they use. Getting an induction motor to provide that variety lowers the efficiency because the controllers are too expensive. For this type of application, new magnet technology is the answer. They run at slower speeds, saving energy; they are also quieter and create less waste heat.
In fact, these permanent magnet motors are getting more and more popular. Because they use less raw material, such as copper and steel, their price points are less affected by the swings of the commodities market. And as their popularity grows, the overall prices of the magnets comes down, as well. Even now they are used in everything from cars to cell phones.
They won't work in every appliance: your Homelite chainsaw, for example, will probably always run on gas. But this motor will make an appearance in many other places, like drills and refrigerators. They have the high torque and multiple speeds of traditional brush motors combined with the silent sturdy build of the brushless motors. A match made in heaven!
dc motor power-op-amp speed controller