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Tag Archive: AC

AC and DC Industrial Motors Are All Around Us

Whether you are a homeowner who’s handy at fixing things around the house or an experienced technician who works with various types of machinery, at some point you will work with industrial motors. You can find them with various horsepower, speeds, voltage, frames, enclosures, and mountings depending on their various uses. Two of the most common engine types are AC and DC, referring to engines that utilize alternating current and direct current, respectively.

AC Engines

This is one of the most common and simple industrial motors, sometimes known as a “squirrel cage” motor. Features include the following:

A Simple Design: This machine is made of three windings in the exterior section with a simple rotating section, called the rotor. The AC line voltage causes the rotor to rotate around the axis. Its speed is dependent on only three things: the fixed number of poles, or electromagnetic winding sets, built into the motor; variable speed drives, commonly known as inverters or amplifiers, that change the frequency of the AC line voltage; and the amount of force or load on the machine. Changes in speed are expected when the load changes.

Low Cost: AC industrial motors are the most affordable engines available if you need more than 325 watts of power, mainly because of their simple design. You can find them in air conditioners, washers and dryers, fans, blowers, vacuum cleaners, and many other products. Because they are so widely used, you won’t have any trouble finding a replacement when needed.

Reliability: Because of the simple design, AC engines are also very low maintenance. There are no brushes to replace and the bearings could last several years or even a decade or more.

DC Engines

DC Engines are preferred in most variable speed and load control applications. Features include the following:

An Understandable and Cost-Efficient Design: A permanent magnetic field is created in the stator, or stationary section, of the motor by either permanent magnets, which are common in fractional horsepower applications, or electromagnetic windings, which are used in applications that need five or more horsepower.

This makes this type of engine easy to design and manufacture. Some of the lower horsepower models are available from $50 to $100.

Speed Control: With this type of machine, controlling the speed is simple. The higher the armature voltage, the faster the rotation, which means a faster speed. The voltage will increase in conjunction with the horsepower. Most DC industrial motors will perform well over a speed range of 20:1, down to approximately 5% to 7% of the base speed. They are designed with variable speed operation in mind, so they have heat control features that allow lower operating speeds.

Load Control: The load, or torque, control is simple. The output torque is proportional to the current, so if you limit the current, you limit the torque it can take. This is one reason why these DC engines are used for applications such as textile manufacturing.

Industrial motors are all around us; homeowners use them whenever they use appliances and power equipment, while a technician may repair several a day. Chances are you’ll use an AC or DC engine before the day is over!