Overheating problem in starter

[shkim2000]

I have problem with overheating in motor stater and the surface of MCCB, magnetic contactor, and cable is very hot. The insulation tube at the terminal lug is almost melted. The rating of cable, magentic contator, and MCCB are correctly selected. I took out the components to bring shop and tested temperature rise test, but the temperature rise is very small, but reinstall those in starter and have same problem. Anybody advise possibel reasons we assume ?

 

[jraef]

Typically a temperature rise such as that in components that are correctly rated is a result of one of 2 things: Duty cycle was not taken into consideration when sizing, or there is a connection resistance problem somewhere.

I'll assume from your slight errors in English that you are not in the US and using IEC ratings. I'm not criticizing your English skills, but you didn't state where you are from and it makes a difference when discussing ratings.

If you simply picked the starter based on AC-3 ratings and your are starting and stopping the motor often enough to need AC-4, then the result would be a hot contactor and the heat would travel up the power circuit to the MCCB.

When you removed and shop tested the components, were any of the connections the same, or did you use new cables in the shop? Also, the type of cable can make a difference. Extra flexible cable (i.e. welding cable) can overheat rapidly if not properly terminated. The extra surface area in all those individual strands can be a problem if not clamped tight enough, and I have found that some brands of contactor clamp type terminals cannot properly camp that type of cable.

More information would be better.

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[powerjunx]

shkim2000,

I think jraef is right. Moreover, try to check the ambient temperature.

As jraef has started, Why not look for an alternative? In your case, im pretty sure that heat will build up if my pressumption is correct; the terminal point of the contactor and conductor is connected through "pressed-connector" - usually aluminum material.
In our MCC, we replaced all this connector to a "bolted type connector" that pave away the culprit such as yours to prevent to happen again. The former, during our maintenance, we found out loosen terminals and a considerable hot spot is transparent. Regarding to MCCB, there's no reason to worry about it.