3 phase motor

[GLENNSPARK]

Its a Hydraulic pump, brand new so it has to run dry until it pumps up the first bit of fluid.

...........

 

[micknew]

Wire the new one in star, it will be fine.

 

[44ALLAN]

Japanese machines with transformers spring to mind [/QUOTE
Yes, but thats not the set up he's got.

I wasn't responding to his set up though..............I was responding to you saying we don't have 200v 3 phase in this country?
Of course we have !!

"By wiring in delta you have put 400V across each windings DOL, it was not designed to take it".

Check his post mate he never mentioned 400v you assumed it

 

[Darkwood]

OP if what he has said has clearly followed his bosses instructions and by the results it would seem neither of them are experienced or competent in motor connection and protection... thus as i see this at a guess as others have said 400v has been injected into a duel voltage motor with connections set up for 200/230 volts hence the motor becomes a heater and melts into a block without the protection operating until a short occurs.

Whichever way you look at this thread we have Electricians working in an area beyond their experience and not understanding why the results have happened...

By the initial question its clear the OP isn't competent in motors
As he suggests he's been overseen by his boss i can only conclude that his boss has no understanding on the basics of motor connection and duel voltage set-ups if i assume this is the error had it been a star/delta motor for our 400v 3ph system then the voltages on the plate will be different and an incorrect star / delta set-up wouldn't turn it into a smoke bomb.

New motors are normally well made and in 25yrs ive only seen 1 faulty brand new motor be faulty once ... if connected and protected right then no matter what the duty of the motor is it should trip if pushed too far...

I have sympathy totally here with OP as an apprentice i was taught by a wannabe 'competent sparkie boss' where in fact getting his socks on the right feet confused him.

 

[Lucien Nunes]

You didn't say how long it took before you got smoke out of the motor, but if the windings were suitable for star-delta then I'd venture a guess that you had the phase sequence wrong on the delta contactor. FWIW the last two squirrel cage motors I saw let out the magic smoke were wired wrongly in this way, because some numbskull had mixed the leads up, and neither had adequate overload protection. See the attached hasty sketch. This motor will start perfectly well and if the load is light it will keep running, but soon catch fire.

I've never seen an HRC fuse that 'failed to trip', nor would I expect to find fuses as the only protection for a 5kW motor. Why would a dry hydraulic pump cause high starting current (apart from because it's chewing itself to pieces for want of lubrication). As usual the OP raises many questions of how deeply it was thought through before connecting up.



NB anyone who can't see what's wrong with this circuit, please refrain from installing any motors!

 

[Darkwood]

OP has wired it as DOL Lucien the confusion here is the motor arrangement star connection or delta, it would give the impression we are talking 3wire connection.

Note to the OP -- dont expect to return the motor as faulty as most issues with motors can be easily identified when stripped down and it will be quite clear cut what happened here to any motor engineer.... this unfortunately will be an expensive lesson learnt.

 

[ChrisElectrical88]

Your gaffer needs to start turning down work he is not competent for. If I got asked to do a three phase motor it would be passed onto a sub contractor who understood the work as I have minimal knowledge on this. Could be a costly mistake.

 

[Pete999]

Personally I would have disconnected the 3hp motor from it's mechanical load and started it DOL wired in Star, can't see why you would want to start a motor that small star delta, wrong phase rotation at this stage would not be a problem with the mech load un coupled

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Personally I would have disconnected the 3hp motor from it's mechanical load and started it DOL wired in Star, can't see why you would want to start a motor that small star delta, wrong phase rotation at this stage would not be a problem with the mech load un coupled

 

[Lucien Nunes]

OP has wired it as DOL

Ah OK, I read it as he had done differently to how he had been asked, but makes more sense the way you say. It's still possible one winding was reversed relative to the other two if the three links were hand-wired wrongly, turning the motor into a self-destructing transformer. I have seen somebody wrestling with that as well although there the motor did have proper O/L protection, he just couldn't work out why it kept tripping straight out.

 

[LeeH]

This motor can run in star or delta and it was wired correctly with links in the correct place for delta. Phase rotation was correct.

Correct, but only 1 way for a certain voltage.....

Take a photo of the motor plate and post it up.