AC vs. DC Gear Motors: What’s the Difference, and Which Offers More Gear Motor Advantages?

Sinotech    February 11, 2013

  Adjustable Speed Motors  15 Watt 70mm

Adjustable Speed Motors
15 Watt 70mm

Ask an engineer to list the differences between AC gear motors and DC gear motors, and you can expect a quick, concise answer: AC motors are generally smaller, less expensive, lighter and more rugged than DC motors. DC motors, on the other hand, are generally considered better for variable speed operations. Their improved speed control makes DC motors more expensive to purchase and maintain, generally.

Given enough time, the engineer might go on to explain the technical aspects that differentiate these two gear motors. If speaking to a layperson, the engineer would begin by explaining that AC stands for alternating current, while DC stands for direct current. A more advanced audience might get information on the basic design of each gear motor – an AC gear motor typically features a rotor inside a stator with coils, while a DC gear motor might have rotating armature windings with a stationary magnetic field.

If you’re reading about gear motors, you’re probably an engineer yourself, so let’s skip to what would interest designers like you: AC gear motor advantages, compared to their DC counterparts.

  • AC gear motor design has advanced greatly in the last few years, to the point where an AC motor can offer as much or even more speed control than a DC motor. Today’s AC motors can be regulated to within .1 percent of the desired speed.
  • DC gear motors are still more expensive, on average. A big advantage of AC gear motors for manufacturers is their lower price. Today, an AC motor and drive together can cost the same as a DC motor on its own.
  • Because they typically require fewer repairs, an AC motor is a better choice for potentially wet, hard-to-reach or otherwise hazardous environments.
  • Technological improvements have brought AC gear motors up to speed with DC motors. For instance, modern AC motors can provide full torque immediately, at startup. That was impossible just a few years ago.

Even with all of these advantages, there are some situations that still demand a DC gear motor or a high performance AC motor. For one thing, engine cooling is crucial for long-term performance, so a premium-efficient or energy-efficient motor is recommended for adjustable-frequency drives. High starting loads and the demand for consistent horsepower while operating 150 percent above base speed are a few other applications that demand specialized motors. The best way to determine which gear motor is right for you is to contact a custom motor manufacturer such as Sinotech. After learning about your needs, an expert can recommend the best gear motor based on its intended application.

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