The control cabinet is usually designed as the central control point for automation and process control equipment. Inside the cabinet are programmable logic controllers, frequency converters and their associated communication and control lines.
Since the electrical control cabinet is usually powered by 480 V, the wiring must usually be routed through the same cabinet as the electronic controller - this is an advantage for troubleshooting and maintenance. You can observe the indicator light on the programmable controller, measure the voltage on the motor starter, and adjust the driver in the same cabinet.
Security should always be a priority before opening a cupboard. When a technician or engineer begins to study electronic controls, it is natural to focus on suspect low-voltage equipment and controls, and it is easy to forget that working in a mixed-voltage cabinet exposes workers to dangerous voltages and short-circuit currents. Know the voltage you're going to see before you open the door.
Industrial control panels must have durable and legible labels indicating the cabinet's rated voltage, phase number and any power frequency. Older panels may not be marked. Many panels now have a curved flash warning label on the panel door. Note that arc-flashing labels usually provide the highest voltage in the cabinet and do not mention other supply voltages that may be present. In addition to any labels, refer to electrical diagrams and supplier manuals, and even step down the system if necessary to help determine the voltage supply in the cabinet.