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Difference between AC and DC Drives


Copy of ACD Image (16)Understanding the distinction between AC and DC drives and their roles in the regulation of speed and power in electric motors can be critical to helping your business. Simply put, a drive is a device that is used to control the speed of an electric motor by altering the frequency of the electrical supply to the motor. AC and DC drives perform this action in markedly different ways and to differing effects. Below, we’ll discuss the distinctions between the two types of drives and help you determine which drive - whether AC or DC - would be best suited for your application.

The Basics

An Alternating Current (AC) drive takes AC input and converts it to DC, then converts the DC current back into AC current. While this double conversion may seem counter-intuitive, the process actually increases the output current exponentially to keep up with modern drives without burning motor oil.

On the other hand, a Direct Current (DC) drive converts AC input into DC current to power DC motors. The DC drive is considered to be much more simplistic than an AC drive. Because of this, a typical DC drive will utilize several thyristors to make either a half or full cycle of DC output from a single or three-phase AC input.

What’s Best for You?

In recent years, the industry is trending towards using more AC drives in motion control applications. Experts cite AC drives as more energy efficient, and therefore more cost-effective than their DC counterpart. Furthermore, AC drives can change speed easier than a DC drive can, allowing it to complete complex tasks quickly. However, the intricate nature of AC drives may make them harder to integrate into older systems. In spite of the lack of durability and consistency of the DC drive over its lifespan, it is still useful in low-speed, high torque applications like a crane. 

Selecting the “right” drive comes down to the application and your business’ needs and preferences. If your application involves a large amount of power and complex changes in speed and direction, the AC drive might be right for you. However, if your application operates in a low-speed, high torque environment, the DC drive might be the best option.

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