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DC vs. AC Electric Motors: What Are Their Differences?

DC vs. AC Electric Motors: What Are Their Differences?

When talking about electric motors, people often have confusion between DC motors and AC motors. The most obvious distinction between these two kinds of electric motors is the type of current that they each turn into energy – DC motors convert direct current, while AC motors convert alternating current.

However, apart from such fundamental distinction, there are many other differences between DC motors and AC motors. To understand how they differ, below are some of the most important pieces of information about the two main classifications of electric motors.

What is a DC motor?

A DC motor is a type of electric motor that mainly converts direct current electrical into mechanical rotational energy. This device can also be used in reverse by rotating a motor shaft to generate DC electrical power. When utilised in such manner, the DC device functions as a generator. There are numerous key types of DC motors available, including permanent magnet DC motors and brushless DC motors. 

What is an AC motor?

An AC motor is an electromechanical device that primarily converts alternating voltage electrical power and current into mechanical energy. This type of motor comes in different varieties, but they can generally be categorised into two main groups: synchronous motors or induction motors. Synchronous motors include hysteresis motors and reluctance motors, while induction motors are either single phase or polyphase.

What are the differences between the two motors?

As mentioned, the primary difference between DC motors and AC motors is the kind of current that they convert. However, aside from this, DC motors and AC motors can also be distinguished from each other in several ways. These differences essentially involve different aspects.

  • Input Power 

In terms of input power, AC motors are known for having the ability to operate with various sources. DC motors are powered with a unidirectional current (one that has no change in direction over time) supplied from a DC power source.

AC motors, on the other hand, are powered with alternating voltage and current that come with direction and amplitude changes upon completion of a wavelength. In essence, AC motors can operate with either a single-phase source or a polyphase source.

  • Speed Control

The speed control of DC motors is dependent upon the variations in the voltage and current that is applied to the armature coils or windings of the device or the adjustments in the current that flows to the field coils. In other words, DC motors usually involve a proportional speed-current relationship.

In contract, the speed of AC motors is controlled by the alternating current frequency that is supplied to the stator coils. As the frequency increases, the motor speed also increases. Hence, the relationship between speed and current in AC motors in directly proportional.

  • Performance

DC motors have the ability to generate high torque and are therefore valuable where speed control is necessary. This type of electric motor can provide a more constant and stable torque over various speed ranges, and it can generally deliver faster response to load changes compared to AC motors.

AC motors, on the other hand, are excellent when there is a necessity for variable torque and high speed. However, it should be worth noting that AC motors usually experience slip and induction current loss. Hence, they can suffer from efficiency issues. In contrast, DC motors are considered to be typically 30 percent more efficient due to their permanent magnets.

There are indeed numerous other differences between DC motors and AC motors. Learning about these differences is useful in picking out the best type of motor that is suitable for your company or organisation. Nonetheless, whatever type of electric motor you have, it is important for you to maintain your machine regularly to ensure optimal operation.

Once your electric motor starts exhibiting issues, do not hesitate to hire a specialist right away who will check your machine and maybe subject it to some electric motor rewinds or repairs. Electric motors are very valuable, so it is necessary to always keep them in their best condition.