Introduction to Industrial Control Panel Design
Whether open or closed, industry standard or built for tough environments, or modular or customized, it is important to follow a set of repeatable tasks when designing industrial control panels for efficiency and safety.
Industrial Control Panels (ICPs) are ubiquitous in industrial control systems. They can be found in both small and large automated systems, as well as a wide range of applications and industry sectors. Industrial control panels contain the heart of a controlled system.
The National Electrical Code (NEC) is a standard for the design and safe installation of electrical equipment in the United States. NEC and related regulations dictate many features of ICPs.
Figure 1. An ICP that follows industry standards and best practices. Image used courtesy of UL Solutions
The governing documents that are used by engineers and designers around the world include the following documents, some applicable to certain geographical jurisdictions:
NFPA 70 National Electrical Code (NEC)
NFPA 79 Electrical Standard for Industrial Machinery
UL 508A Standard for Industrial Control Panels
IEC 60204-1 Electrical Equipment of Machinery
The NFPA 79 defines industrial control panels as an assembly that comprises two or more control-circuit and power-circuit components. Control circuit components include Programmable Logic Controllers (PLCs), Input and Output modules, motor drives, industrial network devices, and field communication protocol wiring. Power circuit components include power sources, Uninterrupted Power Supply (UPS) devices, relays, electrical transformers, and voltage/current converters.
Industrial control panels do not contain controlled equipment or the main power supply. Because they do not house the controlled equipment or machines, ICPs can be seen as the modular control units of an automated system. Another important regulation states that ICPs must work with 600 V or less power. This power threshold is why they do not house the main power supply. Usually, wiring from the power source arrives at a transformer inside the panel, which then steps down the power levels to what was determined in the design.
Figure 2. A crowded section of an ICP containing control and power elements. Image used courtesy of Thermal Edge Inc.
The NEC standard states that ICPs may be open or enclosed, although most panels in the industry are enclosed. Enclosures may be industry-standard or special purpose for tough environments.
In the next section, we will examine some of the most important steps for successful ICP design.
Industrial Control Panel Design Process
Industrial control panels can be modular or custom-built. Modular ICPs are meant for controlling small equipment and automated islands. These modules follow a central design template, with some variations allowed, depending on minor customizations. Modular ICPs can be mass produced thanks to the standardized design.
Figure 3. The ICP of a FANUC robot follows modular design criteria. Image used courtesy of K+S Services
On the other hand, customized ICPs are designed and built for specific applications and automated systems. Because no customized ICP is the same, it is crucial to follow a repeatable design process and industry best practices to avoid building flaws and inefficiencies in the ICP.
The following design steps apply to both modular and custom-built ICPs.
1. Controlled-system Design
The first requirement is a fully, or at least 90% designed controlled system. This system includes all the machinery that the devices in the ICP will control. The controlled system determines the type and quantity of the devices needed; therefore, it is required to decide on basic features, such as overall dimensions and power requirements.
2. Functional Specification
The functional specification includes block diagrams and narrated descriptions to describe the functions of the industrial control panel. This document also establishes the relationships between the components inside the ICP.
Functional specifications can be as comprehensive as desired. The more time spent in this step, the more likely errors can be caught and fixed early. As we know, it is also less expensive to make changes here than to make them later, once the ICP is built or installed.
Building the functional specifications requires expertise. Therefore, cross-functional teams are assembled to review all aspects of the ICP, including mechanical, electrical, and control systems.
3. Layout Design
Once the functional design is completed, the next step is to create the layout of the ICP. The layout design uses CAD-based applications, such as AutoCAD Electrical Toolset, Zuken E3.panel, Smart Draw, Solid Edge, Ansys Space Claim, and more.
Figure 4. 3D CAD design and electrical schematic using Zuken. Image used courtesy of Zuken
Advanced CAD tools offer the ability to design and visualize the ICP in 2D and 3D. The 3D design helps understand physical constraints better, especially in tight spaces.
Many ICP design CAD tools also offer the ability to create the electrical diagram within the same project. As a result, the layout design using these comprehensive software tools saves time and reduces errors. For example, some applications offer recommendations for the best wiring routes based on existing connections and electrical diagrams. Following the recommended wiring route reduces costs as wire lengths are optimized.
4. Electrical Diagram and I/O Diagram
The electrical diagram and the I/O diagram are two very important documents. First, they are deliverables for the customer, who will then use them for diagnostics and troubleshooting.
The electrical diagram contains every connection from all the components inside the ICP. The user will be able to locate and trace connections using this diagram. The I/O diagram is a supplement that includes detailed information about the inputs and outputs of the control devices.
Figure 5. An electrical diagram of an ICP. Image used courtesy of Automation Controls Inc
These documents can be produced using the same CAD tools for the layout mentioned before, but they can also be made using separate specialized electrical software tools.
5. Bill of Materials
One last document to produce is the bill of materials (BOM). The BOM is useful for the manufacturer to order the parts needed and verify inventory levels. It can also be helpful for the ICP customer as a list of parts to have in stock for repairs.
Industrial Control Panels
Whether open or enclosed, modular or customized, following repeatable steps to design an ICP are important for efficiency and safety. In our next article, we will take a look at control panel design concepts, focusing on standards and regulations.