Sister Envy: The Unfortunate Plight of DC Drives

Sister Envy: The Unfortunate Plight of DC Drives

Marcia, Marcia, Marcia.

Many of us who grew up watching "The Brady Bunch" fondly remember poor Jan Brady – the iconic middle child who feels big sister Marcia gets all the attention and has everything going for her.

In many ways, the DC drive is the overlooked sibling on the plant floor. It wasn’t always this way. Just a few short decades ago, DC motors and drives were the favorite for many applications.

However, advances in AC technology – plus the superior maintainability of AC motors – have made AC drives the current industry darlings.    

But while AC drives might win popularity contests, modern digital DC drives have unique capabilities – just like Jan – that often make them the right choice.

Where Can a Digital DC Drive Be the Star? 

Especially in high horsepower applications, rugged DC technology is often still the most cost-effective option. It could be a traditional low speed/high torque application like a crane. Or a harsh steel mill or mine environment. Or any application where regenerative capabilities are critical. 

You may even find legacy DC regulators quietly performing tasks in the far reaches of your plant – isolated from your plant network and other applications.

Because DC motors are both long-lived and expensive to replace, a DC drive can certainly be the star in a system retrofit. Replacing a legacy drive with modern DC drive technology allows you to add network connectivity and digital enhancements to your application – without purchasing a new motor.

The right DC drive can take on a starring role in a new application, too. Modern DC drives not only deliver precise speed and torque control, but also streamline installation, enhance system diagnostics and provide an intuitive user experience as part of a connected plant and enterprise.   

What Can You Expect From a Modern Digital DC Drive?

Although simpler than AC drive technology, a modern digital DC drive borrows heavily from its flashy AC sister. You can expect a smart high achiever that fits right in with the rest of your plant:

  • Network Connectivity. Modern DC drives featuring EtherNet/IP connectivity can make an otherwise standalone DC application an integrated part of your plant control system. Monitor drive and motor status – and performance – just like your AC drive applications.
  • Parameter Based Control and Tuning. Maintaining a legacy DC motor and drive can be time-consuming and costly, especially when it requires manual tuning and multiple hardware devices to accomplish the task. A digital DC drive improves the process with parameter-based control and autotuning.

Parameters can also be monitored via the HMI, stored and shared with other DC drives throughout the network:

  • Diagnostic Capabilities. With a modern DC drive, operators can monitor intuitive and explicit fault codes from the HMI – a significant improvement over manual troubleshooting processes that may still be used for legacy systems.
  • Lifting Load Management. Modern DC drives also deliver digital load management for lifting applications like cranes, hoists and draglines. Take a look at this torque proving (PDF) technology that can optimize the process.

Perhaps most important, modern DC drives enable a consistent plant-wide control strategy and user experience. Taking it a step further, this approach (PDF) unifies programming, configuration and maintenance management in a single software environment.

My advice? As stepfather Mike Brady wisely explained, “Some of us are good at one thing, and some of us are good at another.” So take a closer look at DC technology for your new applications. And search out the legacy DC drive systems in your plant.

Optimize those applications with modern digital DC drives – and give them a chance to shine.

Nancy Rivard
Posted May 21, 2018 By Nancy Rivard, Product Manager, Rockwell Automation
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