Electromechanical Relay – Contact Cleaning

Electromechanical Relay – Contact Cleaning

 

Equipment owners often wonder the importance of maintenance on any variety of equipment. Some owners would even say that electrical maintenance is a waste of money. I have a demonstration of an electromechanical relay with dirty contacts.

 

When watching the video, notice the contact below the coil begins to vibrate. Those vibrations are happening because current is being injected through that instantaneous element. Once the pickup setpoint is reached, the contacts will completely move and make contact to the stationary contacts.

 

When the moving contacts touch the stationary contacts, the contacts are said to be “closed”. These closed contacts will typically be a direct trip to a (86) Lockout Relay or directly to a circuit breakers trip coil.

 

As you can see, the test set does not sense that the contacts closed. What you can’t see all that well, is that there is a greenish oily/greasy residue on the contact. This is a byproduct of the old wire insulation that was used on this relay.

This may cause a problem in the tripping operation of a circuit breaker.

 

So what do you do?

 

Every maintenance cycle, which could be around two to three years, you should clean the contacts. Using a burnishing tool in conjunction with a cotton swab is what was used on the relay in the video.

 

Once again, you can see the moving contacts vibrate. Once the pickup setpoint is reached, the contact touches the stationary contact and the test set senses the closed contact. This happens so fast that you almost need to play the video a few times to see what happened.

 

Do you think maintenance is worth it?

 

Well, my opinion is that maintenance is worth every penny. Keeping electrical equipment maintained and lubricated is what could save a life or even save your equipment. The cost associated with personal injury or replacement of equipment is much more than the cost of maintenance.

 

 

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1 comment on Electromechanical Relay – Contact Cleaning

  1. Great demonstration. This is the perfect example of why its crucial to maintain your electromechanical relays. It’s amazing how something so simple could cause so much chaos if it fails to operate properly.

    Say those little pieces of copper don’t conduct the trip signal, then your breaker fails to quickly clear the fault. Now a breaker upstream has to trip, resulting in unnecessary loss of service. Meanwhile, your equipment takes on additional damage until the fault is cleared.

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