3 phase generator issues

[taninthai]

Hi have  a 3 phase generator last two nights after 2 hours use one of the phases is dropping out no power down it at ,the other 2 phases are fine,,,,,,,,,start the genny next night all phases fine then 2 hours later same phase drops out again......anyone any ideas what needs doing or looking at,,,,,, ,there is no faults on any of the outgoing circuits.

thanks in advance

[RichCor]

Where is the phase drop out occurring -- is this showing up on the gen-set panel indicator or have you double-checked the phase outputs using a handheld multi-meter.

 

While it could be the generator itself, as there may be some fail-safe circuitry protecting the phase, using a multi-meter at the gen-set output would verify the drop-out is occurring at the gen-set ...otherwise take a look at your cabling to the Transfer Switch or CU/Distribution Board and see if any connections are loose or corroded. 

 

I've experienced phase brown-outs or completely power drop-outs due to corrosion on a connection point, in one case it was in an overhead wire mid-point where a splice had been made using a non-copper wire nut that was totally corroded.

[taninthai]

Seems to be drooping out right from the genset,,,have three wires coming out the generator to a 3 phase breaker then out to outgoing circuits,,,the phase is dead going into the breaker ,it’s not tripping the breaker when it drops out,,,,,,,,will add some pictures in a couple of hours.

i know it’s 100% not a problem with outgoing circuits because we have another generator and we have switched to that one when phase drops out,and that runs fine.

[RichCor]

What's the make/model of the genset.

What do the protection circuits on the genset look like, are they in good condition and set to trip together?

What type of maintenance/inspection has it had, especially on contactors, relays and breakers? 

 

If your genset phase protection circuit isn't shutting down the generator automatically on phase loss, that also sounds troubling. 

 

 

[taninthai]

Here is the beast don’t seem to have any relays or contractors red wires comes straight out of genny into top of breaker then black cables out the bottom to outgoing circuits,it’s phase 1 that keeps dropping out,,,,,,,,,last night just connected outgoing circuits onto 2 phases only.

 

[RichCor]

2 hours ago, taninthai said:

Confused by this image

It appears to show UVW N lugs, (ABC N / RST N same same but different ends)

with cables concentric 'taped' as if indicating Phase 1, Phase 2, Phase 3, and 'no tape' indicating potentially Neutral.

 

...but

lug 'U' (traditionally Phase 1) has nothing connected to it

lug 'V' has Phase 1 + Phase 2 connected

lug 'W' has Phase 3

lug 'N' has Neutral

 

While the lugs could be repurposed and just serving Phase 1, 2, 3 ...the two cables on the second lug are still confusing. And this probably has nothing to do with why you can have three phases operating but after two hours the first phase drops out.  But still, very odd wiring.

[taninthai]

No that is what I done after after 1 phase dropped out.....phase u is the one with the problem,,,,,,  sorry the genny is not powering anything 3 phase ,,,,it powers 15 single phase bungalows split over the 3 phases ...so when the one phase dropped out losing power to some of the bungalows I just doubled up onto phase 2.....seems to me it’s something internal in the generator windings and it’s drooping the phase out when it gets to hot or something.

example tonight I could reconnect phase 1 to terminal u and all will be fine for a couple of hours,after a couple of hours I am getting no juice to the u terminal 

[RichCor]

Have you pulled the cover off and inspected the windings for any sign of arcing or discoloration that might indicate a failure in the cover of the winding wire or connections? 

[Crossy]

It certainly sounds like an intermittent connection, field collapse, failed regulator and the like isn't going to affect just one phase.

 

If it's a very old machine with a fixed field winding and the important bits going round with the engine it could be as simple as a failed/worn out carbon brush.

 

Time to pull the end of the genset and have a poke around.

 

 

[taninthai]

Ok job for tommorow open up end of genny and examine ,,,will update tommorow....thanks

[carlyai]

Could you also measure the voltage at UL as the set up is now, after 2 hours and see if the no load phase 1 voltage is present? If it is, It could indicate a temperature sensor problem?

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[taninthai]

46 minutes ago, carlyai said:

Could you also measure the voltage at UL as the set up is now, after 2 hours and see if the no load phase 1 voltage is present? If it is, It could indicate a temperature sensor problem?

Sent from my SM-J700F using Tapatalk
 

Will do,,,,,not had time to open up genny today , so will run it tonight on the two phases and test the voltage on u terminal when start genny and then again after 3 hours.

[RichCor]

If you can also record other runtime stats, before and after using the front panel selector knobs

 

I believe on your genset the three phases are monitored using...

VOLTAGE SWITCH

Line-Line voltage ( U_AB, U_BC, U_CA )

 

CURRENT SWITCH

Line Amperes ( I_A, I_B, I_C )

 

If the phase is truly dropping out, the voltage measured on U_AB and U_CA should also indicate this.

[taninthai]

Ok so started generator with nothing connected to phase 1 and have 240v.....test again 5 hours later and only getting 15v at phase 1.

will open end of generator up later today and add pics

[taninthai]

So opened up the end of genny today not much to see the brushes look fine the rest I don’t really know what I’m looking at...lol

 

What’s this in the pic below some form of regulator 

 

Edited March 4, 2018 by taninthai

[Crossy]

With only two slip-rings that's a rotating field machine, the tin box is either a rectifier for the field or some form of regulator. Where do the wires go?

 

You need to look at the fixed windings to see if there's anything untoward going on, but I suspect you are going to have to get a man in if there's nothing immediately visible.

 

Has the generator itself got any rating plate with a manufacturer / model number? I'll bet there's a maintenance manual on the net somewhere.

[Wirejerker]

I see in your photos one brush spring is loose. You prob knocked it loose with your poking, in case it would not of caused your problem just the other brush would just work twice as hard.
Look at the connections in the bottom right inside the control panel. These should be the connections of the alternator windings. Look for loose connections or signs of hot connections. Good luck and don’t make it a girls look.


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[taninthai]

10 minutes ago, Wirejerker said:

I see in your photos one brush spring is loose. You prob knocked it loose with your poking, in case it would not of caused your problem just the other brush would just work twice as hard.
Look at the connections in the bottom right inside the control panel. These should be the connections of the alternator windings. Look for loose connections or signs of hot connections. Good luck and don’t make it a girls look.


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Ok well spotted ,just had someone look at it and he spotted the loose brush spring,have pushed that back in and will see how it goes tonight

          

 

[taninthai]

So it dropped the phase out within an hour of starting the generator tonight ,,,did a little live testing and I think it’s a faulty 3 phase breaker,got the first phase running through a separate breaker now ,so will see how it goes tonight.

 

 

Set up for tonight??

 

Edited March 4, 2018 by taninthai

[RichCor]

So, how's your breaker bypass patch doing?

 

Interesting issue.

Wonder why that first breaker contact to fail?  Maybe a corroded and arc-pitted contact causing high resistance, but not enough of a head issue to trip the breaker mechanism normally?

[taninthai]

8 minutes ago, RichCor said:

So, how's your breaker bypass patch doing?

 

Interesting issue.

Wonder why that first breaker contact to fail?  Maybe a corroded and arc-pitted contact causing high resistance, but not enough of a head issue to trip the breaker mechanism normally?

The breaker by pass has seemed to fixed the issue,it held in all last night,generator runs for 14 hours a night ,yes bit of a strange one with the original breaker but I suppose you do get faulty breakers once in a while.

thanks for all the replies and help anyway,it’s agreat section of the forum with some members that have good knowledge.

[RichCor]

Hopefully you're planning on replacing/installing with another proper three-phase breaker.

[taninthai]

2 minutes ago, RichCor said:

Hopefully you're planning on replacing/installing with another proper three-phase breaker.

Lol...... off coarse 63a three phase breaker is top of my shopping list.

crossy the green wires of the tin box thing don’t really go anywhere they are just bare ends hanging out,this generator been messed around with a lot by Thais    ,,I think you would have a heart attack if you saw our generator room.

thanks again