Electrical Control Panel failure is one of the dreads of plant maintenance managers. Usually, the control panels in a manufacturing plant are not just electrical in nature; they usually incorporate programmed PLCs and motor drives that require industrial field service beyond the scope of most general electricians.
Regardless of age, electrical control panel failure occurs for various reasons. Knowing what to look for first can help you avoid major electrical control panel failure before any major production or safety issues arise. Here are some common reasons for electrical control panel failure:
Power Spikes and Surges
Many manufacturers design their electrical control panels without line reactors or surge suppressors to guard against electrical spikes and surges. Unexpected electrical events from the power company or the elements can damage panels, leading to lost controller programs, faulted VFDs and damaged electronics. Sadly, much of the damage can be instantaneous. If you have AC drives in your cabinets, you probably should consider exploring how line reactors can help your maintenance program.
Tripped breakers or blown fuses
Depending on how an electrical circuit is protected, an overload will cause a breaker trip or a blown fuse. If your electrical system is acting funky, check for tripped breakers or blown fuses first. These circuits are isolated so the control system could appear to be functioning normally but part of the systems process won’t function.
Cut or grounded wires in the conduit systems
Electrical contractors will often use Electrical Metallic Tubing (EMT) conduit or flexible conduit in places where they be stepped on or damaged by contact. When damaged, the conduit can separate from the wires and cut into them causing them to ground on the conduit or cut in half. This can cause tripped breakers, blown fuses, shorted power supplies and unexpected machine operation that could seriously injure personnel. To prevent this, perform routine inspections of conduit systems.
Tripped overloads on power circuits
Most motor starters are protected using an overload set to the Full Load Current of the motor. If the electrical load on the motor is excessive or the motor windings short, the current will exceed the motors rated full load amps causing a trip. In most cases, the overload is wired using the neutral so when trouble shooting, measure from the neutral on the contactor and not the ground. Additionally, most overloads have an indicator on the front that alerts you when it’s tripped. Correct the problem and then use the overloads reset button to reset the device.
Loose or disconnected wires
Many manufacturers use screw terminals to fasten their electrical wires. These types of terminals are susceptible to vibration that can cause loosening over time, eventually leading to an open circuit that is difficult to troubleshoot due to the appearance of a connected terminal. Regularly inspecting your screw terminals for tight connections will prevent this. Alternatively, many companies, including Innovative IDM, offer spring clamp terminal technology that won’t loosen and rarely has to be checked.
Carbon build up on relay or contactor contacts
Carbon naturally accumulates on contacts that arc when opening and closing. Over time, carbon will cover the contact, blocking conductance through the contactor or relay. An easy way to check is to energize the relay and use a volt meter to measure across the contacts to verify the contacts are conducting. If voltage is read across the contacts, you’re OK. If not, there’s your problem:Use contact cleaner to remove the carbon or replace the component if beyond cleaning.
Electrical control panel failure can be mitigated by following the above troubleshooting measures. While complete failure is not inevitable, maintenance professionals also should keep abreast of the latest technologies and consider modernizing their equipment with a retrofit.
Adam Ring is an engineer at Innovative-IDM and heads up the contract manufacturing division. Ring also is one of the company's founders and original panel builder. You can reach him at firstname.lastname@example.org