OLR Setting

Look on the name plate of the motor, for full load current & set your OLR accordingly.

Oops, wrong answer. No 10% or any other factor is applicable.

Joshi's answer is correct, you should set it at the rated current of the motor (if it is a DOL starter and the FLA is passing through it).

Not quite. If the OLR is in a different ambient temperature location from the motor, some adjustments may be appropriate. With fixed heaters, this can mean a size or two up or down. With adjustable relays, this may mean ± some similar amount. One case of special interest is fan motors in blast freezers at -35°C. The extra cold air can allow actual amps to be something like 20% above normal FLC.

Most IEC devices available in India are ambient-compensated. In fact the good ones are "under-compensated" by 0.4% per °C to take into account the difference in thermal mass between the OLR and the motor. US-style eutectic alloy relays are not ambient compensated as you rightly point out.

I see how an ORL can be ambient-compensated for its own ambient, but not for the motor's ambient if different. The IEC doesn't address this?

Please revisit #6

Irrelevant. I am not talking about the thermal mass of the motor; I am talking about quite different ambient temperatures at the OLR versus the motor.

i believe it does. Hence the under-compensation, which actually is implied in IEC 60947-4 vide this figure...

The non-trip/trip gates are 1.05/1.2 at 20°C, and 1.00/1.2 @ 40°C. This, to me, allows for the higher thermal mass of the motor. If the relay wasn't ambient-compensated, it would trip unnecessarily at a lower current, over-protecting the motor. i do believe that the ambient compensation is actually to prevent nuisance tripping of the relay, if they are both at the same ambient. If the relay is in a controlled ambient say 20°C, and the motor is toiling at say 40°C, there may be an unprotected zone (1.00 - 1.05) but this is statistically ignorable in view of the better performance in most other conditions (both at same ambient, motor at different but not too high an ambient, etc). Just my opinion.

+20% of FLC is acceptable for c class insulation. also you have to mind the connections

* or D

Grossly incorrect! Only Joshi & KVS are correct. The OLR must be set to - not more than - the rated full load current of the motor. However, one can set the OLR to less than the FLC of the motor, if the motor is oversized.

RTFM.

You can set the overload to whatever you want, but if you set it to more than FLA you are going to shorten the life of the motor if it runs above FLA.

Not necessarily, as in the blast freezer fans described previously.

refer

Table 430-148 (From 1999 NEC) or

Table 430-150 (From 1999 NEC)