3 phase motor

[Guybrows]

I wired a 3 phase motor for a hydraulic pump up today. Its a 3kw motor. My boss told me to wire it as a Direct online in Delta. I thought maybe it would be better as a Star Delta as the pump would be dry and it may cause high start up current. I belief that a small motor is fine as a DOL. When i turned it on the motor kicked out a load of smoke and the cable started to overheat. The fuse was faulty and didn't trip. I tested mega tested the winding and they were down to 0.02 ohms. Something not right. The supplier says they have never had a faulty motor but I cant work out why a 3kw motor would draw enough current to blow the windings. I am now going to wire the new motor it in star delta just in case but thought I would see if anyone had any ideas on how a motor could blow like this.

Cheers

Guy

 

[micknew]

It should have been wired in star.

 

[netblindpaul]

It depends on the motor spec how it is wired, and why should a hydraulic pump start up dry, if it does then you have bigger fish to fry than star or delta motor connections for DOL or even star/delta starting, because none of these will fix your problems.

 

[micknew]

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

 

[Marvo]

.....the motor kicked out a load of smoke and the cable started to overheat....I tested mega tested the winding and they were down to 0.02 ohms. Something not right..

This could be the understatement of the day

It would cause winding damage if you incorrectly wired it or if it was locked rotor or if there was a phase missing. You wouldn't normally protect a small motor like this one with fuses, there should have been a manual motor starter or a thermal overload in the circuit.

Running a 3kW motor DOL is fine unless it's a special application that requires particularly high starting torque.

 

[micknew]

Bet you had to alter the links to connect in delta.

 

[Guybrows]

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.

 

[micknew]

I've never seen a 3hp motor run off a star delta starter (possible though).
The motor would be fine in delta if the supply was 230V 3 phase, not 400V.

 

[netblindpaul]

Glad the rotation was correct, else you could well have goosed the Hyd pump after a few revs!

 

[Guybrows]

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

 

[netblindpaul]

I've never seen a 3hp motor run off a star delta starter (possible though).
The motor would be fine in delta if the supply was 230V 3 phase, not 400V.

Are you serious? :whatchutalkingabout

 

[Knobhead]

The motor should be wired as stated on the plate. Hydraulic pumps have to be primed and bled before powering up.

Three HP is a tiny motor and should be fine for DOL, so long as it’s connected as stated on the maker’s plate.

 

[Guybrows]

How do you wire a 230v Delta? Is that not just star?

 

[micknew]

Are you serious? :whatchutalkingabout

Yes, for DOL.

 

[micknew]

How do you wire a 230v Delta? Is that not just star?

We do not have 210/230V 3 phase in this country.