A comprehensive guide on industrial panel design

Introduction

Industrial control panels are critical components for automating and controlling industrial processes and machinery. These panels contain closed metal boxes that enclose electrical components like switches, relays, controllers, and circuit breakers. An industrial control panel centralizes connections to peripheral devices, allowing experts to control and organize production objectives. An intelligently designed industrial control panel optimizes operational efficiency and reduces downtime. This guide discusses the essential factors to consider when planning an industrial control panel.

Types of industrial control panels

Different types of industrial control panels cater to various manufacturing facilities. Each type of control panel comprises distinct components where an individual component is assigned a particular function, such as turning the machine on or off, regulating motor speed, guiding various movements, controlling valve openings or closures, and performing numerous other operations. Some of the commonly found industrial control panels are:

• Motor control center (MCC) panels: The MCC is a consolidated assembly designed to oversee the operation of one or more electrical motors. MCC panels pack control components such as variable frequency drives (VFDs), programmable logic controllers (PLCs), electrical metering devices, pushbuttons, and indicator lights. A common bus bar interconnects multiple enclosed sections where each section houses power contactors, protective relays, isolators, and other control and indication devices. The MCC also houses protection and safety devices such as an iron reactor, earth fault relays, phase reversal relays, circuit breakers, fuses, and a power disconnect switch.
• Programmable logic controller (PLC) control panels: A PLC control panel consists of PLC, analog and digital I/Os, HMIs, power supplies, ethernet switches, pushbuttons, relays, circuit breakers, and terminal blocks. Based on the input signals from sensors and other devices, these PLC panels control the essential functions of monitoring and controlling outputs, generating alarms, regulating valve operation, and stopping/starting a process.
• Power distribution panels: The power distribution panels distribute electricity from the source to where the current is used. A typical power distribution panel packs circuit breakers, transformers, and other devices that protect equipment from electrical problems. Other peripheral devices include connectors, terminal blocks, voltage regulators, power distributor modules, wires, and power factor correction equipment to ensure the power supply's quality.

Figure 1: An industrial control panel

Parameters to be considered while designing an industrial control panel

A well-designed control panel should align with functional requirements, application specifications, and regulatory standards. Some of the key considerations involved in a control panel design are:

• Right enclosures: It is essential to choose an enclosure of an appropriate size to hold the panel components. The panel designer needs sufficient space for component wiring and installation. Although increased volumes raise costs, a small enclosure is rarely the best choice and may only save money initially, disallowing future expansion. Furthermore, the heat produced by the electrical components may overheat the control panels. These panels should thus be of adequate volume and be appropriately designed. They must allow sufficient airflow among components for heat dispersal. The correct enclosure for industrial control panels will shield the components from hostile environmental conditions, ensure safety, and comply with regulatory standards. Some common types of enclosures used for industrial control panels are:

  • Polycarbonate plastic enclosures are more affordable than metal enclosures. Their high impact resistance property makes them suitable for indoor and outdoor applications. The NEMA ratings for polycarbonate plastic enclosures range between 1, 3R,4, and 4X.
  • Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer known for its toughness, impact, and heat resistance. ABS enclosures protect electronic components, devices, and equipment from environmental factors such as dust, moisture, and impact. They come in various shapes and sizes, and their design may include features like mounting tabs, ventilation slots, and connector openings.
  • Fiberglass-reinforced plastic (FRP), or glass-reinforced plastic (GRP), is a composite material of a polymer matrix reinforced with glass fibers. It has high impact strength and rigidity with a working temperature range between-31˚F to 300˚F. It is cost-effective and has excellent electrical properties, moisture, and chemical resistance.
  • Polyester is a thermoplastic known for its high performance, produced through injection molding. It exhibits notable impact resistance, though it is less resilient in cold temperatures than polycarbonate. With outstanding electrical properties and superior resistance to chemicals and moisture, polyester maintains its functionality across a temperature range spanning from -40˚F to 248˚F.
  • Mild steel is a type of carbon steel that contains a low amount of carbon, making it relatively malleable and easy to give desired shapes. It is commonly used in electrical enclosures and protects control panels in wet, non-corrosive spaces. These enclosures come with NEMA ratings 1, 2, 3, 4, 6, 12, and 13.
  • Stainless steel enclosures are durable, long-lasting solutions for protecting your industrial control panels. These panels are fire-resistant and perform well in wet environments. Stainless steel enclosures are highly durable and attractive and can provide grounding for metal conduit and metal-sheathed cables. Stainless steel enclosures NEMA ratings range across 1, 3R, 4X, and 12.
  • Aluminum is highly reliable and corrosion-resistant, suitable for indoor and outdoor applications. Additionally, aluminum alloys can withstand high temperatures and offer natural EMI/RFI shielding to prevent interference. It has 3, 3R, 4, 4X, 12, and 13 NEMA ratings.
• Thermal Management: Electrical, electronics, and control items are usually vulnerable to high temperatures and thermal failures. The heat generated by electrical devices in enclosures can directly affect the reliability and service life of the equipment. Depending upon the environmental conditions, the size of the cabinet, and the heat load, several thermal management products like filtered fans, heat exchangers, and air conditioners can be considered for a particular application.
• Wireway Design: Choosing the right type and amount of wireway design is essential. The correct choice of wireway allows easy termination of internal wiring to internal panel components and makes the wire labels legible. Devices should be free of any wires in front of them. Wires should not run diagonally, as horizontal and vertical runs add useful slack and help keep the panel neat. Also, the rightly sized wireway leaves room for future wiring additions when components are added to the panel. Devices and wires should be kept separate from high-power elements. For example, CAN bus and Profibus wires should not be near the main power supply cables. Electromagnetic noise from these cables can affect the transmission capabilities of control and bus cables.
• Component Placement and Layout: Components and component groups should be functionally and logically organized as necessary for any control panel. For instance, components with a high voltage rating should be placed at the top right of the panel, aligning with the standard positioning of the main incoming power disconnect switch in most control panels. As the panel designer descends the control panel, power components will feature progressively lower voltage levels. To facilitate straightforward troubleshooting, power distribution components should be accompanied by a breaker to the left for the specified power level, followed by distribution breakers, fuses, and terminals. Consistency and organization are maintained, reflecting the hierarchy depicted in schematics. Enough space should be left between groups to allow for convenient expansion when necessary. Below the power distribution components, I/O terminals and PLC racks should be positioned. Since components at the top emit more heat due to their higher voltage, sensitive or heat-sensitive components should be placed near the bottom. This arrangement enables most heat to escape towards the top of the control panel. Additionally, since field instrument I/O wiring is typically directed toward the bottom of the control panel, placing I/O terminals at the bottom facilitates easier wiring.
• Labelling: Labeling the wires, terminals, and components inside a control panel is essential as such an action makes them easy to maintain and repair. Labeling is a time-saving strategy that allows technicians to perform routine maintenance and repairs efficiently on the panel. For PLC, outputs and inputs should have a label with a syntax corresponding to the PLC address. However, for non-PLC I/O wiring, the label is assigned according to the line number in the schematics. The wire should be labeled per terminal number if the wiring is connected to a power distribution terminal. Power supplies, breakers, and other panel components are often labeled with abbreviated prefixes identifying the component. For example, "AC120" is used for 120VAC power distribution, and "DI" is used for digital input. After that, a number is added to identify the terminal group.
• Documentation: Creating a comprehensive document at the end of the control panel design process is essential to capture all necessary information. It is crucial to control panel modifications and repairs and helps save money and time. Correct documentation includes electrical schematics, test results, installation instructions, program copies, functional specifications, panel drawings, and maintenance procedures. It should also contain the information needed to troubleshoot issues, make modifications, and perform maintenance.

Regulatory standards for industrial control panels

An industrial control panel follows different standards and regulations for design, production, and installation. These standards are due to the different types of components present inside the panel. Compliance with these standards is essential for all control panels for guaranteed safety and optimal performance. Some of the popular regulatory standards for industrial control panels are as follows:

• NFPA 70: The National Fire Protection Association 79 (NFPA 70) establishes guidelines for wiring standards within the National Electrical Code (NEC). This section focuses on electrical and electronic components used in industrial machinery, particularly those operating at or below 600 V. The regulation includes associated electrical equipment, including industrial control panels and other distributed components integrated into the machinery. NFPA 79 protects machinery operators and facilities from electrical hazards and fires, ensuring equipment safety and ongoing work processes.
• National electric code (NEC): This regulation is widely used to ensure electrical equipment and wiring installation. The NEC requires a specific radius for incoming and outgoing power connections for wiring clearance. Once an industrial control panel is ready, NEC® Article 409 applies. NEC® Section 409.22 requires that an industrial control panel cannot be installed at a location in the circuit where the Available Fault Current (AFC) exceeds the control panel's short-circuit current rating (SCCR).
• Underwriters laboratory (UL)508A: The UL 508A standards for control panels are designed to give clearance for devices that produce heat, including Variable Frequency Drives and Programmable Logic Controllers. The main aim is to ensure there’s adequate room for ventilation. It also includes recommendations for protecting individual control circuits, maximum permitted loads, proper internal and external wiring, and display location. The UL 508A certification protects quality and integrity while meeting public safety standards.

Key components of a control panel

An industrial control panel assembles different components or parts in standard and systematic arrangements. The connection of components determines the overall design, operation, and control of the machine or process function. Figure 2 represents the key components present inside the control panel enclosures.

Figure 2: Inside view of Industrial control panel with necessary components

1. Programmable controllers: A Programmable Controller is a specialized digital computer in industrial automation and control systems. PLCs are designed to perform control functions, automate processes, and manage machinery in manufacturing plants, factories, and other industrial settings.

2. Variable frequency drives: A variable frequency drive (VFD), alternatively referred to as Variable Speed Drives (VSDs) or Adjustable Speed Drives (ASDs), is a motor controller that regulates the speed of an electric motor by adjusting the frequency and voltage of its power supply. The VFD can manage the ramp-up and ramp-down of the motor during start and stop operations, respectively.

3: Industrial connectivity: It is needed for transmitting process data from field-level devices or machines to industrial automation control systems. Industrial connectivity also allows central control rooms to tap into the extensive data generated across factory floors, facilitating remote factory management, centralized production planning, and real-time diagnostics.

4: Motor starters and control: A motor starter is an electrical device that makes the motor start-up and stop stable and provides electric motor protection. It is essential in industrial and commercial applications where electric motors are employed. Motor starters offer a controlled and safe way to initiate and interrupt the power supply to the motor.

5.Surge protection Devices: They protect electrical and electronic equipment from voltage surges or transient voltage spikes. These surges can have various sources, including lightning strikes, power grid switching, and other electrical disturbances. Surge protection devices divert excess voltage from sensitive equipment and protect them from damage.

6.Smart relays: They are compact and programmable control devices that combine the functionality of traditional relays with advanced programmability and communication capabilities. Smart relays are commonly used in automation and control applications where a level of intelligence is required to manage and coordinate various processes.

7. Circuit breakers: Circuit breakers are devices that protect electrical circuits and equipment from damage caused by excessive current flow or short circuits. This crucial component in electrical systems interrupt the flow of electricity in the event of a fault or overcurrent.

8.Safety controllers: These are specialized devices that manage and ensure the safety of machinery and processes in industrial settings. Safety controllers are designed to monitor and control safety-related functions, help prevent accidents, protect personnel, and maintain compliance with safety regulations.

9.Relays: These are electromagnet activated and electronically operated. Relays pull a set of contacts to either connect or disconnect a circuit. They have a vital role in various applications, providing a mechanism for the remote control of circuits, automation, and protecting electrical systems.

10.Power supplies: Power supplies provide electrical power to various components within a control panel and play a vital role in energy management and automation technology. They ensure that the electronic and electrical elements inside the panel receive the necessary voltage and current for efficient operation.

11. Manual motor starters: Manual motor starters serve as electromechanical protective devices within the main circuit. You can use them to control the activation and deactivation of motors manually. Manual motor starters offer fuseless protection against short circuits, overloads, and phase failures.

12: Contacts and connectors: Contacts and connectors play pivotal roles in the design and functionality of control panels. These in-panel elements ensure effective electrical connections and signal transmission.

13. Wires & Cables: Wires and cables help in seamless transmission of electrical signals and power between various components. They provide the necessary connections for switches, relays, and other devices, ensuring effective communication and control within the panel.

14. Fans and fan accessories: Panel fans precisely cool heat sources within an enclosure, effectively preventing the creation of hot spots. These fans can be horizontally or vertically mounted and can cater to various applications. Fans are equipped with guards to safeguard against accidental blade contact, and often feature speed controls or thermostats for airflow regulation. In some applications, air filters are employed alongside panel fans to enhance air quality by eliminating dust, pollen, and other particulate matter. This helps safeguard equipment from damage and contributes to minimizing maintenance costs.

15. DIN rails: DIN rail is a standardized metal strip commonly used in control panels, distribution boxes, and automation systems. You can use the DIN rail for mounting electrical and industrial control devices within equipment enclosures. DIN rail terminal blocks help to connect and organize electrical wires on the DIN rail securely. These terminal blocks provide a convenient and efficient means for wiring in industrial applications, ensuring a reliable and structured electrical connection.

Figure 3: Front view of industrial control panel with necessary components

16.Human machine interfaces (HMIs): An HMI presents a textual or graphical representation of system conditions and operations, offering essential information not available with basic pushbutton panels or switch banks. HMIs provide robust capabilities for monitoring, control, status reporting, and various other functions.

17. Panel instrumentation: Panel instruments are devices or tools integrated into control panels or instrument panels to monitor, measure, or display various parameters, processes, or information relevant to a system or operation. These instruments provide real-time data, feedback, or control functionalities within a specific panel or control setup.

18. Data acquisition systems: These are components and processes that collect, measure, and record data from various sources. These systems typically include sensors, signal conditioning equipment, data acquisition devices, and a computer or controller for data processing and storage. The primary purpose of data acquisition systems is to capture information from the physical environment, transform it into digital format, and provide accessibility for analysis or control applications.

19. Emergency stop switches: These are also known as E-stop or kill switches. E-stops are safety devices designed to interrupt power to a machine or system quickly and easily in emergencies. These switches are prominently placed and easily accessible, allowing operators or personnel to shut down equipment in a hazardous or critical situation rapidly.

20. Enclosures: These are boxes that house the control panel, and usually made from metals or plastics. The enclosure ensures the safety of the panel. Enclosures come with a UL safety rating, an IP rating, and an NEMA classification.

21.Tower light: Tower(stack) lights indicate the status of machines, systems, or processes in illuminated and audible forms. They are available in various colors, in blinking or continuous mode, LED, or filament lamp, and with audible alarm options.

22.Indicators: A panel indicator or simply indicator is a device or component on a control panel that provides visual information about a particular aspect of a system. Operators can use the indicator to quickly and easily assess the status or condition of a specific component or process.

23.Switches: Panel switches are connecting/disconnecting switches affixed directly to distribution panelboards and switchgear. They activate and deactivate electrical loads using a swiftly responsive external operating handle.

24.Panel Knobs: Control knobs or panel knobs are manually operated devices typically found on electronic or mechanical equipment. These can be rotated or turned to adjust settings, parameters, or values associated with the device. Panel knobs often have markings or indicators to show the current setting, and can be a crucial interface component for users to fine-tune or control different functions of the equipment.

25.Locks and keys: They secure access to a control panel or enclosure. These locks restrict unauthorized access to the internal components of electrical panels, machinery, or other equipment housed within an enclosure. The system typically includes the lock mechanism installed on the panel and a corresponding set of keys to open the lock.

MRO tools for control panels

Maintenance, repair, and operations (MRO) tools for control panels are crucial for efficient functioning of industrial equipment. These tools are indispensable for the upkeep, troubleshooting, repair, and installation of components in the control panels. Common MRO tools for control panels include:

Industrial control panel solutions from Multicomp Pro

Farnell also stocks a versatile collection of affordable components, tools, and test equipment under the Multicomp Pro brand. This collection helps control panel design engineers, technicians, and production facilities to identify high-value alternatives whilst assuring production-grade quality they can rely on. Customers purchasing from the Multicomp Pro brand can benefit from reduced upfront costs and product-lifetime savings. Here are some key components that facilitate design and development of control panels:

Conclusion

Industrial control panels play an important role in the operation of industries, factories, and various applications by overseeing the diverse electrical processes within a system. The intricate nature of control panel design involves numerous individual components and elements. This guide aims to present a concise overview of the fundamental design considerations. Recognizing the depth and complexity inherent in control panel design, as well as the significance of adhering to application specifications and regulatory requirements, Farnell has forged partnerships with suppliers. This will help facilitate the design and development of industrial control panels, offering valuable support to engineers and technicians, ultimately saving time and costs.