Topics: loose connections at the motor Junction Box
on General Discussion
loose connections at the motor Junction Box
Is there a technology to predict loose connections at the motor junction boxes usually mounted on the sides(motor) . Will IR Scans work at these junction boxes where the motor leads are connected. My Aim is to predict the loose connections at the motor Junction Box where the leads are hooked up.
10-10-2013 11:39 PM
You need a spring washer. May be it goes the other ways, but it is effective.
10-11-2013 01:54 AM
Thanks Kolin . but is there a way to predict if there is a loose connection without opening the junction box
10-11-2013 04:40 AM
Of course there should be many solutions to predict the loose connection, but you know, we have to considerate the cost. Our engineer can do anything if the cost can be endured. One base of effective performance, we pay more attention on the cost..You know, the market is hard.
10-11-2013 07:04 AM
Thanks Kolin. The above question is to ponder over the ideas to see if there is any technology . I understand that the cost is going to come with it but for now i am more interested in learning the technology and the next step would be to ponder on the financial aspects.
Once again thanks a lot fro your contribution.
10-11-2013 09:29 AM
Actually ultrasonic measurements can detect the eletrical noise when there is a bad connection. If a problem is suspected just loosening the bolts holding the cover by a turn will allow much more ultrasonic energy to escape to confirm if there is a problem. Using IR measurements will also detect if the J box is hotter than normal. This can be as simple as using a $20 non contact themometer while a high end thermal camera will also give you a nice picture. Another option is electrical signal analysis but this needs expensive equipment and ideally modules in the MCC with a pass through connection.
Never remove the cover on any energized equipment unless A) there is no other option and B) you have the appropriate PPE, training and procedures in place. If measurement indicates a problem then shut down, lock out tag out and then remove covers for detailed inspection and correction.
10-11-2013 11:50 AM
I understand the intent of your question, but to answer it how it was asked - you cannot "predict" a loose connection, unless you have a high vibration environment and a termination that is not positively captured. An example of a "positive capture" termination is a ring terminal, where there is no open side so the stud remains completely encircled by the terminal metal.
Derek has pretty much covered the available options. To repeat / summarize:
1. Ultrasonic measurement will pick up the "noise" resulting from a poor connection.
This method does not require removal of the cover, or additional equipment as part of the box.
2. Infra-red measurement will "see" the thermal difference between surfaces, including the high temperature area of a poor connection. The method requires through holes in the box material that has had optical windows emplaced therein. These need to be located such that there is a direct line-of-sight to the area of interest that does not pass too closely to another potential hot spot. The method also requires a monitoring camera that is calibrated to the specific window properties.
3. Use of a non-contact temperature measurement ("thermometer") is fairly cheap, but requires a bit of ingenuity to mount safely and still be able to determine the temperature of a given connection.
4. Signal monitoring at the MCC is possible, but still a high-priced alternative. It also generally requires someone who knows what they're looking at, to sift through the signals and get a feel for what's actually happening.
If the connections are energized, keeping the personnel safe is the primary goal. Do not open unless absolutely necessary, use the correct PPE, and follow lock/tag out procedures.
10-11-2013 02:10 PM
Thanks a Lot Derek and Chris.
I had couple of other questions related to this
1) Do you guys we can detect the loose connection on the motor by using IR Scans on the other end in the MCC.
2) Does the heat from Motor Influence the temperature difference at the J box.
10-11-2013 04:46 PM
Yes there is a way to predict connection degradation and do something before any dangerous conditions exist. It is simple and easy to implement in any electrical product. It can also be automated by using typical controllers.
I developed this method (I suppose it could be called a "technology" as I'm told to say) about 25 years ago at a former employer who manufactured electric space heaters. Good electrical connections are quite vital when you make space heaters (12.5 Amps at 120 VAC when on the "high" setting).
However, with GREAT FRUSTRATION !!!!! , I have to say that I cannot explain how because it is an idea currently being reviewed for a possible patent application (because it is so easy, and is so "microcontroller friendly", and yet VERY powerful ------- several young engineers have finally convinced me to try and make it into a product).
However, It's a terrible thing to know EXACTLY how to help someone BUT NOT BEING ABLE TO DO IT !!
If you are serious about this question, and are willing to sign a non-disclosure agreement, then I CAN tell you. However, I would need to charge a small consultation fee -- depending upon the level of assistance you wanted.
10-11-2013 07:27 PM
IR scans can not detect loose connections on the motor at the MCC, IR will only measure the temperature of what it is looking at, so if you are looking at the MCC terminals you will get a temperature measurement of those terminal lugs or tails, depending of the temperature difference between the three terminals you can see current imbalance as one leg may me higher than the others which is easily measured with tong testers, or loose terminals at the MCC, as for the terminal box on the motor yes heat from the motor can easily gain access to the terminal box, and this will always depend on the box construction, and the KW rating of the motor. the best way to check motor terminal leads is always to check in a periodic test but tighten with a torque spanner so as not to stretch the terminal treads.