HI FRENS
CAN ANYONE TELL THE SAVERITY OF THIS PROBLEM , CAN EXPLAIN WHAT IS THE EXACTLY PROBLEM?
I HAVE CHECKED LOAD WHICH IS 10 A UNBALANCED( 10 MORE IN MIDDLE PHASE COMPARE TO R & B) AND TERMINATION TIGHTEN , STILL THE IR IMAGE IS SAME WITH 8 DEG TEMP DIFFERENCE.

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Center phase had 10A more, but what was the value on the other phases? Or what was the fractional change? Or just give us all three phase readings.

I am not particularly familiar with what this is. Looks like maybe a separable quick-connect connector?

Could be your hotter appearance on that center phase is result of three things:
1 - Higher current in center phase as you alluded.
2 - It looks like you have 6 cyclinder-looking things, two per phase. And they are kind of creased/bent (is that normal? beats me). The creases on this particular set give you a view more directly toward the interior of this cluster will it will be the hottest. You can't really see into the corresponding spot above the bottom phase pair.
3 - Less ambient heat transfer away from center phase.

Note that the tail-off in temperature on the center one as you follow the cable to the left doesn't appear tremendously more on the center cable than on the top cable. That also suggests that the difference in current is the big factor causing the center phase to be elevated.

Do you have any more like this you can compare to?

Bottom line - tough call. If the distribution is something like 30A on the other phases, 40A on this phase, , I would just chalk it up to difference in loading. If less percent differenced than that (i.e. higher current levels all thre phases), I would be inclined to fail conservative and call for disassembly/inspect on a routine basis.

hi dear
this is an image of 110KW MOTOR WHICH RUNNING ON FULL LOAD ALMOST. R - 150 Y-160 B- 150A AMPS. THERE IS NO HOT SPOT EVEN AT CONNECTOR.

THE SAME CAPACITY STAND BY PUMP IS RUNNING WITH SAME LOAD . ( SAME UNBALANCED LOAD) BUT ITS IR IS SHOWING ONLY 3 DEGREE DIFFERENCE IN R PHASE.

HOW WE CAN REACH TO ANY CONCLUSION?

THANKS

I too am not 100% clear about the equipment involved. If it is a "quick connect" to the motor, I suggest you have a bad connection. What concerns me the most is it appears to have a fairly large gradient between the point of heating and the surface we see; this means it could be much hotter internally. I would urge frequent monitoring to see how it behaves and, if you can get access to an outage, to look at it physically and perform other testing, such as a resistance measurement (comparing phases).