Soft Starters, VFDs, or ATLs: Which Motor Control Wins? - HECO

Motor control systems are evolving rapidly, and with them, the expectations for reliability, safety, and efficiency. Whether you’re replacing a legacy system or looking to improve process performance, it’s important to understand both the strengths and limitations of today’s most common control solutions.

With decades of experience in a variety of industries and applications, HECO has extensive expertise in installing, maintaining, and replacing modern motor controls.

In this post, we’ll walk through the three primary types of motor control systems, including Across-the-Line (ATL) starters, Soft Starter Systems, and Variable Frequency Drives (VFDs), highlighting the benefits and drawbacks and summarizing the best use cases for each.

Across-the-Line Starters: Tried, True, and Basic

Think of Across-the-Line Starters as an all-go option for motor controls, like a light switch for light bulbs.

Pros
These starters are the simplest and most widely used control systems for motors. They offer direct online starting, meaning full voltage is applied to the motor as soon as it’s energized. These systems are cost-effective and offer basic motor reversing capabilities with minimal setup requirements. There is also less technical knowledge required to work on these components, making them more serviceable by in-house maintenance professionals without a specialized service call.

Cons
What ATL systems offer in simplicity, they lack in protection and control. There’s no ramp-up or ramp-down speed control, just instant power. That translates to high in-rush currents, potential mechanical stress, and no real-time speed control. They also lack the safety features, programmability, and system integration offered by more modern solutions.

Bottom Line
ATL starters are the cheapest for a reason. This is probably your best option if you have a motor and don’t have mechanical stress concerns, power supply concerns, and you don’t require speed control capabilities.

Soft Starters: Gentler Starts, Smarter Stops

Serving as the middle-of-the-road option, Soft Starters bridge the gap between ATLs and VFDs in terms of cost and features.

Pros
Soft Starters help motors ease into full speed by controlling the voltage and amperage during startup. This minimizes in-rush current and reduces mechanical stress on the motor and connected systems. Compared to ATL systems, Soft Starters offer better feedback and more built-in safety features, including Safe Torque Off options on many models.

They’re particularly useful in processes with multiple starts per cycle, as they reduce strain on components and limit voltage dips that can affect other systems.

Cons
While Soft Starters offer improved control during startup, they do not provide full-speed control throughout the motor’s operation. Once the motor reaches full speed, a Soft Starter essentially steps aside, offering limited influence on operating performance.

Bottom Line
Soft Starters are a good middle ground for operations looking to reduce wear and tear without needing full-speed control. The ability to control in-rush currents at start-up also reduces energy costs.

Variable Frequency Drives (VFDs): Full Control and Flexibility

VFDs go a step further to offer speed control during the ongoing operation of a motor beyond ATLs and Soft Starters.

Pros
VFDs deliver comprehensive control over motor speed, torque, and acceleration. They adapt to system demands in real time, improving energy efficiency and extending equipment life. These drives are highly programmable and integrate well with plant control systems using various communication protocols.

Modern VFDs come equipped with Safe Torque Off features and advanced system monitoring, including input/output phase monitoring, torque feedback, and thermal data. Many utilities offer incentives or rebates for using VFDs due to their energy-saving potential, and certain models even allow for power regeneration.

Cons
With greater capability comes greater complexity and higher upfront cost. VFDs require proper setup, integration, and ongoing maintenance to deliver their full value. That said, when implemented correctly, the long-term savings and performance benefits often outweigh the initial investment.

Bottom Line
If you need fine control, improved efficiency, or high-performance system integration, VFDs are the best fit, especially for critical or variable-load applications.

All Systems Go

No matter which control method you’re using or considering, HECO can help you maintain, upgrade, and optimize it. Our motor control specialists offer turnkey installation, system troubleshooting, preventative maintenance, and retrofit support.

Ready to modernize your motor control strategy? Contact HECO to schedule a consultation or Predictive maintenance visit today.

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