Industrial control panels are the enclosed spaces where electronics responsible for the powering and controlling of a machine are housed. These control panels take power from incoming power, typically from a 120V or 240V outlet, which subsequently powers devices such as motors or actuators to perform work or lower voltage 12VDC or 24 VDC circuits for responsive and safer control. From its role into powering machinery to controlling machinery, the control panel is as much the brains of an industrial machine as it is its beating heart.
In industrial controls and automation for factory machinery, control panels are one of the most, if not the most, crucial pieces of hardware a machine has. Whether or not considerations need to be made for scalability, environmental compatibility, incoming voltage, or other factors, knowing what components to select can streamline the control panel fabrication process to allow you to complete your job without having to filter through the plethora of information regarding each component.
CONTROL PANEL FABRICATION:
REQUIREMENTS AND SPECIFICATIONS
When starting off as a beginner control panel fabrication technician, it is important to layout the general series of components that your panel requires as per the design specifications of your build or use case.
Consider the following questions before initiating your control panel building project:
What voltage will my control panel and its corresponding actuators be running?
Where will my control panel be located? Are there environmental or corrosion factors that need to be considered?
How many inputs and outputs does my system have?
How do operators want to control the machine? Is there a preference of pushbuttons versus touchscreen control?
How will wire travel when outside the control panel to external devices?
It is important to explore the questions above—and any more relevant questions to your build—to establish the initial principles and guidelines of the build before corrections need to be made that end up wasting time or money in the long run. The engineering team responsible for the design of the build needs to define these specifications according the customer's requirements to prevent any issues regarding communication and what the expectation is in terms of the functionality of the final product. If this is not the case, it is always best practice to communicate with the customer to ensure that what is being built is both to expectations and more importantly will perform the way that it is intended.
ELECTRICAL ENCLOSURES
The enclosure is one of the most important components in control panel building and will house almost all of the internal electronics of your machine. Your electrical enclosure will likely be determined by two factors—size and environmental compatibility.
Experienced panel builders can acknowledge that many underestimate the ideal size for a control panel, and that many panels end up being undersized for the application. In a practical setting, picking a enclosure that just fits all components outlined in the panel's schematic tends not to be a best practice as it does not factor in future scalability in the case that the customer looks to upgrade their capabilities in one panel. Less space makes the build more difficult with tedious and tight installation and maintenance and potentially hazardous as well, as heat generating components require free space to operate without long term damage.
Environmental compatibility is typically rated through the NEMA enclosure rating system. General purpose enclosures are recognized under the NEMA 1 to NEMA 4 and 4X ratings. NEMA 1 enclosures provide mechanical protection along with some resistance to debris such as dirt; NEMA 2 enclosures provide much the same as the NEMA 1 rating with the added benefit of limited water drip protection. NEMA 3 sees a more robust build with weather resistance to ice, rain, sleet, and windblown dust in both NEMA 3 and 3S enclosures. NEMA 4 and 4X enclosures are typically top of the line with corrosion resistance and wash-down resistance along with comparable or better weather-proofing than the NEMA 3 enclosures.
An enclosure outfitted with heaters or air conditioning can provide a solution to extreme weather situations. HVAC systems for enclosures can often allow electronics to continuously run in optimal temperatures being protected from heat or cold depending on the region. If needed, a panel builder should opt to look into HVAC solutions to ensure functionality in the long term.
For enclosures, it is optimal to choose as big of an enclosure as your selected space allows. More space makes the build process simpler by allowing for larger wire duct and room for components—which in turn makes any maintenance operations easier. Selecting an appropriately rated NEMA enclosure for your application will save on the expense of buying an enclosure that is over-specified or under-specified for your use case.
OVERCURRENT PROTECTION: FUSES AND CIRCUIT BREAKERS
Fuses and circuit breakers are the primary means of overcurrent protection for an industrial machine. The basic premise is when too much current runs through an overcurrent protection module, a fuse or breaker trips and opens the circuit preventing damage. Both fuses and circuit breakers are sized for the control system's amperage and should not be oversized so that the breaker trips at the targeted amperage and should not be undersized to prevent nuisance tripping. Overcurrent protection is an absolute necessity to ensure the functionality of your machine along with ensuring both machine integrity and operator safety.
Fuses are commonly used for overcurrent protection for cost-efficiency due to the prices of individual fuses and fuse holders compared to circuit breakers. When a fuse is tripped due to overcurrent, the fuse is spent and requires replacement with an identical fuse. The need to replace fuses can be a consideration as fuse costs can grow overtime depending on how many instances a fuse trips.
Circuit breakers are a reusable form of overcurrent protection. Instead of using controlled electrical and thermal damage to open circuits, circuit breakers are electromagnetically operated to open a circuit when overcurrent incidents occur. As such, circuit breakers are reusable and can make up for the expense of buying replacement fuses over a longer span of time. Depending on standards such as UL 489 and UL 1077, circuit breakers can be used for branch circuit protection or for specific devices as supplementary protection.
Between fuses and circuit breakers, a decision can be made when considering ease of use and cost over use for long periods of time. If the need to manually replace and repeatedly pay for spent fuses, circuit breakers may be the optimal choice for your application.
CONTROL MODULES: PLCS AND RELAYS
PLCs and relays are control modules that allow for the operation of motors and other high voltage devices through lower voltages. By using a medium such as PLC or relay, higher voltage circuits can be isolated from operators for safety while maintaining regular and even expanded functionality.
Mechanical relays are electronic switches that open or close via electromagnet depending on if a voltage is applied. When a voltage powered the relay's electromagnet, it either closes a circuit in a NO configurated relay or opens a circuit in a NC configurated relay. This input to the electromagnet allows a lower voltage to determine the on-off state of the coil and the higher voltage circuit.
PLCs computerizes the input and output switching process into a centralized, simple controller module. While not directly being able to control high voltage circuits, PLCs can reduce the overall amount of relays in a complex control system for simplification and less wiring. Software made specifically for PLCs are used to program an operation of machine with simple code for repeatable processes, which allows for sensor integration for automated machines to be intuitive.
A combination of a PLC and mechanical relays are a typical control system input where PLCs deliver low voltage signals to relays to activate their corresponding high voltage devices. Relays can usually match the number of high voltage devices, while a single PLC can operate low voltage control through tens of inputs and outputs depending on a model selected.
OPERATOR INTERFACING: PUSHBUTTONS, LEDS, AND HMIS
The means by which a machine's design allows an operator to control its function makes a difference in how easy your machine is to use over repeated use along with how easy it is to train a new operator to work efficiently. Operator interfacing comes in the form of the buttons, keyboards, and screens used to control and monitor machine processes. These modules can be as simple as on and off buttons to touchscreens that display process information in real time.
A typical operator interface for an industrial control system usually consists of pushbuttons, selector switches, and LEDs. Pushbuttons are switches that initiate a process upon pressing a button and often connects to a PLC to provide an input signal. Selector switches provide the same functionality with multiple states depending on the amount of positions the switch has. LEDs are often placed on the control panel or a separate connected module as a visual status indicator for key processes of a machine.
HMIs are dashboards, typically touchscreens, that provides comprehensive information regarding the machine's operation. This data can come in the form a virtual display of a process or instruction, information on the I/O or what is on or off, a display of data collected from the process, and many others. Since the HMI is a screen akin to a computer screen, it is unlimited with what information can be shown by the programming and not at a hardware level compared to a set of LEDs. These HMI modules are more expensive than LED on-off displays with the tradeoff of a higher technical capability.
Choosing between standard control modules and HMI systems comes down to balancing ease-of-use with having a more intricate machine interfacing system. Touchscreen controls are intuitive for most people in industry in 2024, but the actual learning to operate the device through a touchscreen may not be as intuitive as standard pushbutton and switch control. Communicate with your customer to identify the best control scheme for their machine.
SUMMARIZING CONTROL PANEL FABRICATION FOR BEGINNERS
Control panel building is a detailed process with many different components and different configurations depending on what a customer needs out of their machine. The most important priority is to ensure functionality within the conditions that are outlined by the project—ensuring that the electronics have a proper enclosure, ensuring power to the electronics is regulated in full, ensuring that electronics can be controlled to allow for processes to be done properly, and making sure operators can interact with the machine in a relatively easy manner.
At D&R Machine, our engineering staff designs and builds controls and automation solutions for customers in industries for new machines. Our approach to the control panel building process prioritizes the requirements for your application while saving you expenses and delivering with shorter lead time compared to other shops. From initial fabrication to post-delivery support, D&R Machine's control panel building is second to none for reliability and guaranteed performance.
For more on control panel building or other controls and automation projects, contact D&R Machine for a quote and allow our expertise to make a difference for your company.
Comentários