Motor Tripping and Abnormal Noise

Mechanical obstruction? Fish out the rag or stick or whatever it is?

Thankx for the reply.

Rgds,

-SV

Good luck. I was just guessing, so it might be something else.

How old is the motor?

2950 RPM for such a big motor can make a lot go wrong.

Bearings may look and roll normal at low speed, but may act different under full load. You should describe the noise better and do a vibration check to know the bearing status.

Sometimes the shaft to the rotor connection is troublesome, or windings may be loose.

Does the motor have collector rings?

What is the nature of the load on this motor, intermittent, constant, e.g

Hi, thankx for the reply:

1. Motor is more than 10yrs old.

2. No. Motor has no collector rings.

3. Load is constant - for typical heat medium circulating pump.

Rgds,

-SV

Is it a reliance USA motor?

Made for 50 Hz? Did it run too hot?

Yes.. Its Reliance motor... 415Vac/50Hz..

No. Not run too hot..

abnormal noise and tripping problems observed whilst running.. as explained and few trial runs taken on no-load conditions too.

• From experience, the last time a motor tripped on overload was on a sewage sludge centrifugal pump. The cause of the trip was found to be a 4m length of blue polypropylene rope that had become wrapped inadvertently around the impeller and shaft within the pump casing. Once the rope had been removed, the pump no longer tripped; performance close to the original design intent resumed thereafter.

Do bear in mind that the only people who can see the posted pump, and are in a position to investigate, are the Original Poster and immediate colleagues; the pump cannot be seen from here.

Thankx indeed for your valuable reply.

Rgds,

The forum does not know to what the motor is coupled. An "Electrical Engineering problem" approach may be too limiting. Take the blinkers off!

Oopps...! The motor is coupled to Heat Medium Circulating pump (continuous operation ) on offshore process platform.

Consider the possibility of something being inside the pump other than what would be expected.

<unsubscribes>

Sounds like you sucked up some seaweed, or perhaps a grouper....

• Case 2: the problem of poor performance on 2 out of 3 sludge pumps connected to the same inlet manifold and the same outlet manifold was eventually traced to the presence of a 6in square offcut of glass-reinforced polyester roofing material that had inadvertently found its way into the upstream tank and had become lodged part of the way along the inlet manifold.

All good fun. :-)

Strip the pump and motor, you'll have to do it eventually so why wait?

You still haven't isolated the problem, disconnect the leads at the motor then close the breaker, then you'll know if it's in the supply or the cable. If it trips again then disconnect the leads at the breaker and test again. Now you can concentrate on the motor and load, though I suspect it's mechanical.

Troubling in your descriptions is that breakers were tripping after the OL tripped, including a MAIN breaker tripping When the motor was unclupled! That points to an electrical problem for sure.

I would continue focussing on insulation failures somewhere. Often times when people perform an insulation check, they only check the phase to ground reference. If there is a phase to phase short, that will not show up.

Electrical problem is certainly the first place to look in a marine setting....the salt air is unbelievably corrosive...

What you've decribed remind me of a motor being provided inadequate utility power. If you monitor the line to line voltage of the motor starter before and after energizing, you might find that there is inadequate utility power available ... and probably due to power line loss (too long, inadequate ampacity, temperature rating, etc.). The motor will start at a lower voltage than will allow it to run continuously. If you have an inadequate utility power supply, the line current will slowly increase in response to the line to line voltage decreasing, and because of increasing load as it comes up to speed. I've seen this effect many times ... usually an A/C unit at the end of a utility line that is only inadequate on really hot days. If the neighbor wouldn't also use their A/C units .. it would be a non-problem.

I disagree. Low line voltage would not explain all of his symptoms, ie the Main breaker tripping when the motor was UNCOUPLED.

Perhaps you misunderstood.

Un coupling doesn't necessarily adress the problem.

Not low line voltage at startup. Gradual low line voltage during start up and what should be steady state operation. The condition I describe is not necessarily a constant ... and is a function of other's also using the utility source, the weather (A/C required), etc.