The Scoop on AC, DC, and Brushless DC Motors

Electric motors use either AC (alternating current) or DC (direct current) to convert electronic energy into mechanical energy. These two types of electric motors are designed and constructed differently and generate and transform energy in different ways. A decent grasp of electricity and how it works is necessary to understand how alternating current and direct current motors are different. Electricity, unlike light or heat, is not commonly found in nature. An electric current is created by the movement of electrons along a conductor. The terms alternating current and direct current refer to the direction the electrons move along the conductor.

Not surprisingly, the electrons in an AC motor flow along an alternating current and those in a DC motor flow along a direct current. The electrons are constantly flowing forward in a direct current, whereas in an alternating current, they switch directions regularly, and flow alternatively backwards and forwards.

Thomas Edison discovered electricity by observing how a wire placed close to a magnetic field caused the electrons to flow in a direct current. This flow was a result of the north and south poles of the field attracted and repelled the electrons.

For the building of items that requires direct current electric motors, like refrigerators or electric wheelchairs, brushless DC motors are the most highly recommended, as they are easy to maintain and more reliable than their brushed counterparts.

 What makes Brushless DC Electric Motors more desirable?

To start with, brushless motors have very few moving parts. Only the commutator moves, so there are far less things that can go wrong with operation. There’s also very little friction involved, which means less wear and tear and better overall performance over the life of the engine. This also reduces sparks, heat, and noise, making brushless motors safe to operate around gas engines.

These engines operate by using three or more electromagnets placed on the outside of the commutator by having three (or more, but usually three) electromagnets held together by a ring around the outside of the commutator. When switched on, the electromagnet pulls the opposite pole toward it, while simultaneously repelling the identical pole. The commutator then starts to move in a spinning motion. This motion is connected to a driveshaft or gearbox, which drives the generated power to whatever the motor is propelling.

Six components make up a DC motor:

  • Rotor
  • Commutator
  • Axle
  • Brushes
  • Field magnet
  • Direct current power supply

Brushed and brushless DC motors are available. Brushed motors offer simple control of motor speed and high reliability at a relatively low cost.

Brushless DC Motors are widely used in a number of applications. In addition to those previously mentioned, they are most commonly found in the IT industry. Desktop computers, for example, can house up to three DC motors, with one in the cooling fan, one in the hard drive, and a third in the DVD drive. A more high end application where DC electric motors are used is in the growing industry of hybrid and electric vehicles.

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