Understanding AC Drives and DC Drives in Motion Control Applications

A drive is a device that’s used to control the speed of an electric motor by changing the frequency of the electrical supply to the motor. They play a critical role in the overall performance of motion control systems by delivering consistent and reliable electrical supply to the motor, even during rapid speed changes. 

These drives come in many different sizes and forms, but at the most basic level, they can be AC drives or DC drives. Understanding the difference between them can help you understand which would be best for your application. 

The Difference Between AC Drives and DC Drives in Motion Control

An Alternating Current drive, or AC drive, takes AC input and converts it to DC, then converts this DC current back into AC current. This double conversion may seem counterintuitive, but the process increases the output current tens or hundreds of times to keep up with modern, sophisticated drives without burning up the motor coil. 

The Direct Current drive, or DC drive, is more simplistic. These drives convert AC input into DC current to power DC motors. Typically a DC drive will leverage several thyristors to create a half cycle or full cycle of DC output from a single or 3-phase AC input.

Trends in AC Drives and DC Drives in Motion Control

In recent years, DC drives have fallen out of favor in a wide range of motion control applications. They can be regarded as lacking in durability and consistency, costing more over their operational lifespan. Although, DC drives are still a common option in low speed, high torque applications, such as in a crane. 

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AC drives have become a more popular choice in just about every other type of motion control application. AC drives are usually considered more energy-efficient, reducing operating costs. Further, they can change speed more rapidly than DC motors. However, these performance benefits do come at the cost of more complex designs. 

AC drives and DC drives play critical roles in the regulation of speed and power in electric motors. While AC drives have become more popular, DC drives still have their place in niche applications. 

Understanding the difference between these two drives, and in which types of applications they’re best suited for, can help you find the best drive for your motion control application.