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7 ways AC motors are superior to DC motors

30th June 2021 Print

Both AC and DC motors convert electrical energy into mechanical energy used to power various appliances. For example, refrigerators, drills, blenders, and dryers all use electrical motors to generate power. However, some appliances use AC motors, while others use DC motors.

What’s the difference between an AC motor and a DC motor?

The difference between motors is that an AC motor generates power from alternating current and a DC motor generates power from direct current.

AC motor basics

An AC motor generates a rotating magnetic field that creates an electrical current in the rotor, which forms another rotating magnetic field. As the two rotating magnetic fields interact, the motor turns.

DC motor basics

Current flowing through a DC motor generates a magnetic field in the stator and around the armature winding. The armature winding already forms a magnetic field, so when the two magnetic fields interact, the force makes the armature rotate.

Both types of motors can be used in just about any appliance, but will have a different impact on how the appliance functions. For example, drills use DC motors, which allow for precise speed control. When the voltage is increased, the power increases. That’s why you can buy 8-Volt, 12-Volt, or 20-Volt drills.

Although there are some advantages to DC motors used in specific applications, there are more advantages to using AC motors when you don’t need precise speed control.

1. AC motors require less maintenance

When you have a choice between using an AC or DC motor, an AC motor is usually the best choice. For example, when you need to replace an outboard boat motor, an AC induction motor is the superior choice. Not only is an induction motor 30% more efficient than a DC motor, but there’s only one moving part, which means it’s less likely to need maintenance.

2. AC motors are more durable and last longer

When choosing a motor to power an appliance, manufacturers choose AC motors for things like compressors, conveyors, fans, computers, pumps, refrigerators, and HVAC equipment. These kinds of appliances are used frequently, but don’t require much torque, so even when used frequently, the motors last longer.

Appliances that require stable torque and high speeds (like a vacuum cleaner) are best suited to be equipped with a DC motor. The only problem is, DC motors tend to burn out faster than AC motors because the usage is just harder on the motor.

3. Control over speed and torque

With a DC motor, you can’t control the speed and torque with any sort of precision. That’s fine for applications that don’t require precision control, but you need an AC motor when you need that control.

4. AC motors provide accuracy

Since AC motors can be synchronous, they provide the accuracy required to run things like clocks, robots, metering pumps, timers, and speed controllers. For industrial applications, AC motors power precision drill machines and other industrial equipment.

5. AC induction motors match almost any load demand

AC induction motors power standard kitchen appliances, fans, cars, air conditioners, water pumps, and compressors. They’re great because they can match the load demand for just about any industrial or household application.

If you have a choice between a DC motor and an AC induction motor, the latter will serve your needs better.

6. You can adjust the speed of an AC motor

Certain industries need speed control. For example, machinery used in the marine industry, on land, in power plants, and industrial water-cooling equipment all require speed control. AC motors make speed adjustable by changing the number of permanent magnets available for use in the motor.

7. You can get a brushless AC motor

Perhaps the best way AC motors outperform DC motors is with a brushless AC motor; it’s the best of both worlds.

A brushless motor has an electronic circuit board with a sensor that keeps the motor spinning. A brushless DC motor doesn’t lose power to friction, but it’s still a DC motor. However, a brushless AC motor gives you a more energy-efficient motor.

You’ll still need a brushless DC motor for precision control with your drill, but for many other applications, a brushless AC motor will do the trick.

DC motors have their applications

Despite AC motors lasting longer and providing several key advantages, DC motors do have their place. However, when you don’t need the precision control provided by a DC motor, an AC motor is usually the better choice.