30kw Induction Motor Run In Star Continuously

Rated Voltage/ Current? Looks to be 40A around in that case for the DOL the starting current would be much more than the 100A and that may be the reason.

Hard to understand what you are referring to. DOL starter, main contactor? What's the difference? What does running in Star have to do with this?

Let's start over.

You have a 30kW motor. What's the nameplate data for it?

What is your line voltage"

What kind of starter to you have, DOL? Star-Delta? Something else?

How have you wired it up, as in what kind of conductors and what size did you use?

The Motor is running since so many years might be 30 years. Earlier it was run with rotor resistance starter and 10 years back it was connected to DOL starter in a feeder of L&T make panel MCC with 415 volts line voltage. Since then also it was working very well. But recently, Feeder's main contactor melted out while starting.

The motor terminals u2, v2, w2 are permanantly shorted with links and u1, v1, w1 are connected to the feeder with line voltage 415v.

I checked the cable for damage but its ok. not damaged. Checked the motor winding and it also found ok.

I Changed the contactor with new one and started the motor. It is running well. The starting currentwhen checked with clamp meter was going upto 140Amps, and coming back to 25 amps for continuous run and I run it for 10 hours. No problems found till.

But the contactor is getting heated up. Don't know whether this one also fail or not?

"earlier it was running with rotor resistance starter"

Now, you have started confusing everybody. Does this mean that the motor is a Slip Ring Induction Motor?

Yes, curiouser and curiouser. Are you sure it was a ROTOR resistance starter, or was it a Primary Resistance Starter? If it is a Wound Rotor Induction Motor and you have the slip rings shorted out, the starting current will be extra high, much higher than a standard contactor that is rated for thie running current can handle. A typical induction motor will draw 600% current on startup and contractors with motor ratings are made to handle that. But a WRIM with shorted slip rings can draw upwards of 1000% starting current, much more than the contactor is designed for. if you meant a Primary Resistance Starter used on a standard induction motor, that's a different animal.

I would check the wiring voltages to make sure your delta leg is properly located...

Are you sure? 30kW motor connected in star and running with DOL? I very much doubt.

Permanent star mode- that means the motor might be oversized for the application

Without answers to my questions we don't know what this means. Some motors are designed to be connected in Star for one voltage, Delta for another. Speculating without proper data can result in people going off and doing things they should not be doing.

I agree...What are your voltage readings. Was the starter new and destroyed in a single attempt to start, or over the course of time, how much...Is the motor wired in star,or do you have a high leg and wired in delta...Does the fan turn freely, is it belt drive, is the belt adjusted properly, are the bearings good...What is the amp draw on start-up, and after start...Have you done any diagnostics on the motor, what were your readings..

One possibility is that the contactor closed onto a short-circuit. It's difficult to see from here.