PLC Panel

Have you ever wondered: what are all of the components that get installed into a PLC panel and why are they needed? Well you’re in luck! We will take a deeper look into the internal workings of a common PLC panel and it’s components…

Put simply, a PLC panel is a special steel box that contains electrical components required to run a factory machine or process. PLC stands for Programmable Logic Controller, an industrial hardened computer usually found inside factory control panels. High voltage components are what makes up a lot of the other items found inside. What are the other components? Let’s take a look at the two types of components:

PLC Panel: Power Components

Rotary Disconnect

This is where the electrician connects the incoming power wires. It can come with fuses or not. It rotates using the black or yellow handle on the door of the panel to turn power on or off

Power Distribution Block

This is a block usually made of machined aluminum. It has a couple larger wire connecting holes in the top, and multiple smaller wire connecting holes below. It is used to take a large wire and split it up into smaller wires for use with many different components in the PLC panel

Branch Circuit Breakers

These are used to protect against short circuit (and overload in some cases) for each load, such as motors, heaters, etc.


This will convert the high power voltage down to a lower control voltage for common control devices such, as a PLC or HMI

Power Supply

This will convert the high power voltage down to a lower safe control voltage for common control devices, such as a PLC or HMI

Motor Starter

The motor starter (or contactor) turns on motors at full voltage and full speed

Variable Frequency Drive (VFD)

This type of motor controller is able to adjust motor speed and also monitor other motor data as well

Motor Soft Starter

This motor controller starts a motor slowly over time, ramping up to full speed

PLC Panel: Power Components

Supplementary Circuit Breaker

This is used to protect expensive control components and devices of the PLC panel

Master Control Relay (MCR)

A master control relay is a used to implement a safety circuit that will remove power from all output devices in the event of an emergency. It is usually paired with a red mushroom-head pushbutton

Ethernet Switch

Used for network communications between smart devices, the PLC, the HMI, and other components

Programmable Logic Controller (PLC)

The PLC is the industrial computer that communicates and controls all the components, motors, and devices in the machine or process

Human Machine Interface(HMI)

The HMI is the graphical display that the operator uses to configure and operate a machine or process

Input/Output (IO) Module

This is the interface module for connecting wiring from the PLC to the components and devices to be controlled

Operator Pushbutton

A pushbutton the operator uses on the front of the panel to control the machine or process

Terminal Blocks

These are used to connect and splice internal panel wiring and field device wiring

Ok, so you read through all of this. Still confused about what’s inside a PLC panel or how to choosing the right components? Need to bounce your questions off an expert? Contact Us

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