Electrical Control Panel Failure: 6 Prevention Tips

Posted February 23, 2016 by Pepper Hastings

Categories: Blog, UL508A

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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.

electrical control panel failure: fried wires

Industrial electrical panel failure has many causes. Yet many are preventable.

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.

 

Adam Ring

Ring

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 adam.ring@iidm.com

10 Responses

  1. "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 the contacts are conducting, and conducting well, there will be very little voltage drop to be measured. If the contacts are open, you'll see the full voltage across the contact. Dirty contacts will show something in between. This method is also useful for finding blown fuse without removing it for continuity checking.
    • Thank you for your comment John. I agree with your response.
  2. In your paragraph on Carbon build up, you assumed that there should be voltage across the contacts of an energized relay. Since you didn't state whether these were Normally Open or Normally Closed contacts, there is room for error. Assuming that you are talking about contacts that should be closed, these should have LESS than a few mV across the closed contacts to be 'OK'. A larger voltage would indicate too much contact resistance. Of course, an open set of contacts could have any or no voltage, and this is not an indication of malfunction.
    • Thank you for your comment Lance. I agree with your response.
  3. An interesting article. I would like to add the following. 1) Modern electronics have short circuit protect on the outputs that prevent damage. Transient Voltage Surges are by far the biggest cause of electrical failures and can be prevented. In-line inductors are there to prevent noise and will not prevent damage due to voltage surges. The use of high quality TVSS installations will protect valuable electronics. 2) Circuit breakers tripping is not necessarily a failure of the control panel. The circuit breakers are there to protect the electrical and mechanical systems from overloads or faults. If a motor stalls and the circuit breaker trips, if it protects the motor from damage then it has done its job. 3) Conduit should be installed to provide sufficient protection from the surrounding environment. Sometimes the Electrical Metallic Tubing (EMT) is not right for the application. Poor installation practices can leave burrs on the ends of tubes that can cut through insulation. Use of good engineering practice should be encouraged to prevent this. 3) Tripped overloads protect motors from overheating and damaging the winding insulation due to a mechanical overload. When it trips, it is doing what it was intended to do. 4) Copper conductors in screw terminals, if properly tightened, rarely come loose. Modern terminals are designed to be resistant to vibration. It should not be necessary, but they can be checked on an annual or biannual maintenance schedule to prevent it ever becoming a problem. 5) I have not seen carbon build up being a problem on good quality modern equipment. Look for designs that have extended surfaces path between circuits..
    • Thank you for your comments Chris. You make excellent points.
  4. Energize the contactor or relay wo anything connected to the contact points and measure across the closed contacts with an ohm meter. If they are no do the same. Should be basically 0 ohms.
    • Thank you for your comment Richard. I agree with your response.
  5. Thanks for this great information about Control Panels and its benefits. Keep posting more such content that are really helpful to others and add a great value.

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