PLC to VFD: The ABCs of Control Panels

Anyone who has been in a manufacturing environment has likely come across a control panel at some point in their career. Almost every piece of equipment that we produce here at Innotech comes with controls of some kind. Even a simple on/off switch is technically a control, and from there they can get much more complex.

As a UL 508A certified panel shop, we work with these items all the time. But perhaps you’ve come across a TLA (three-lettered acronym) and wondered ‘what does that stand for?’ or ‘what does it do’? This article is a quick overview of a few components that we work with on a daily basis when designing and building automation equipment and/or integrating line control. We’ll look at:

• MCC (Motor Control Center)
• PLC (Programmable Logic Controller)
• HMI (Human-machine Interface)
• VFD (Variable Frequency Drive)

MCC (Motor Control Center)

An MCC is a cabinet, housing or other enclosure that contains multiple electric motors in a single location. [1] The motor controllers share a common power feed which can also include control panels, PLCs, and other controls. They are typically found in large industrial buildings where it makes sense to house motor controls in a central location. 

PLC (Programmable Logic Controller)

A PLC is rugged computer built for industrial applications to control a manufacturing process. They come in many sizes and configurations, from simple analog setups to complex digital devices with thousands of inputs and outputs. They were originally developed in the 1960s for the auto industry to replace mechanical relays [2], but can now be found on practically every manufacturing floor where automation is involved. Functionality has changed dramatically since then and now includes relay, motion, and process controls as well as networking. In system integration applications, the PLC is replaced with an industrial server that is able to control real world devices along with advanced data collection, monitoring and reporting functions. 

HMI (Human Machine Interface)

HMIs allow people to interact with machines. In the early days of computing, inputs had to be painstakingly created with clunky manual machinery and then fed into the computer by hand. Eventually User-Interfaces (UI) were created with the goal of making computer operation easy, efficient, and enjoyable. [3] Control panels using HMIs vary from simple push-buttons to digital touch screen.

VFD (Variable Frequency Drive)

VFDs are motor controlling devices that vary the input frequency and voltage to control the speed of a motor [4]. VFDs can be used in a number of applications and offer quite a few advantages, such as energy savings, increased efficiencies, and control performance. These devices can be stand-alone (such as those that operate the belt drive on our Innotech Lug Washer), or they can be incorporated with other controls into a single control panel.

Bringing it Together

Controls come in a variety of shapes, sizes, configurations, and functionality. Understanding these individual components and bringing them together in a seamless fashion is one of Innotech’s core strengths. Whether it’s a single machine needing to be networked or an entire process line build from the ground up, we can work with you to ensure your team meets your production goals. Get in touch with our team to discuss your next automation project.