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Old 06-03-2012, 05:32 AM   #1
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Default generator sync problems

G'day people,
Just wondering if any of you guys could put me on the right direction with this problem....Im working on a barge at the moment and they have two 215kw gensets when they are run by themselves with normal load on the boat its about 24amps each phase on both generators then when they are paralleled it jumps up to about 250Amps on both without adding any other load.. i was thinking reverse power but it doesnt trip.... any help would be appreciated.

cheers Brenden
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Old 06-03-2012, 05:46 AM   #2
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Why are you running them both at the same time? I would of thought one would be the backup.

If you run both of them together and the mechanical speed is different you could create voltage spikes between the two gensets. This would explain the high amp draw.

Also change your user name
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Old 06-03-2012, 06:11 AM   #3
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because the bow thruster motor is 200kw and draws 400A FLC also improves fuel efficiency. Both speeds were about 1505RPM any other suggestions?

ha i'll change mine to QLDlecky then
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Old 06-03-2012, 06:26 AM   #4
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because the bow thruster motor is 200kw and draws 400A FLC also improves fuel efficiency. Both speeds were about 1505RPM any other suggestions?

ha i'll change mine to QLDlecky then
No other suggestions sorry, I don't really deal with generator's unfortunately. You've caught ET at a bad time (early morning for the US) Most of the guy's that could help you are probably asleep at the moment.
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Old 06-03-2012, 06:35 AM   #5
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what make/brand/model are the generators. are the generators set up to sync. have you talked to the distributor/manufacturer that they were purchased from to see if you could get the hardware you need to sync them. if you are just ganging them together and hoping that they work you are likely to be dissapointed, and you might be in for a generator suprise.

I found a link that might help. look around for some articles on your specific generators and see if you can find hardware to autosync them
http://web.thomsontechnology.com/pdf...ingEB018R0.pdf
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Last edited by wildleg; 06-03-2012 at 06:39 AM.
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Old 06-03-2012, 07:09 AM   #6
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Quote:
Originally Posted by aussielecky View Post
G'day people,
Just wondering if any of you guys could put me on the right direction with this problem....Im working on a barge at the moment and they have two 215kw gensets when they are run by themselves with normal load on the boat its about 24amps each phase on both generators then when they are paralleled it jumps up to about 250Amps on both without adding any other load.. i was thinking reverse power but it doesnt trip.... any help would be appreciated.

cheers Brenden
So you are doing this with a load of 24 amps? Do you have better success with a larger load?
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Old 06-03-2012, 07:46 AM   #7
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sounds like they are not in sync when you close the circuit between the two.
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Old 06-03-2012, 10:03 AM   #8
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check to see if there's a droop setting on the voltage regulators. sounds like reactive load, and that's why you're showing the large currents when they're running in parallel. I'd also take voltage readings (w/same meter) on each gen set when they're not in parallel, in case there's a calibration issue w/a panel voltage meter. doesn't take a large diff in output voltage settings between the 2 sets to get that current. good luck!
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Old 06-03-2012, 01:30 PM   #9
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If both gens are grounded wyes, there will be circulating current between them. This current will be reduced as they warm up, but it'll still be there.

250 amps sounds more than a bit excessive for circ current though.

They are almost certainly in synch, otherwise far more severe problems would have occurred. Like parts flying around and smoke......

Is there any kind of load-sharing relay installed?

Usually, two gens of the same manufacturer, rating and age will get along just fine.

As noted, if there's not enough droop in the regulators, the gens will fight with each other.

Also, just because the reverse current relay doesn't trip doesn't mean there is no reverse current. Relays do go bad occasionally.

Given the current values, I'd almost suspect that one engine is coasting (as in no fuel) and the other gen is motoring it. Are the engines electronic?

That's all I can think of at the moment......
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Old 06-03-2012, 01:36 PM   #10
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If both gens are grounded wyes, there will be circulating current between them. This current will be reduced as they warm up, but it'll still be there.

250 amps sounds more than a bit excessive for circ current though.

They are almost certainly in synch, otherwise far more severe problems would have occurred. Like parts flying around and smoke......

Is there any kind of load-sharing relay installed?

Usually, two gens of the same manufacturer, rating and age will get along just fine.

As noted, if there's not enough droop in the regulators, the gens will fight with each other.

Also, just because the reverse current relay doesn't trip doesn't mean there is no reverse current. Relays do go bad occasionally.

Given the current values, I'd almost suspect that one engine is coasting (as in no fuel) and the other gen is motoring it. Are the engines electronic?

That's all I can think of at the moment......


I love watching videos of out of sync gennys blowing up.
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Old 06-03-2012, 04:12 PM   #11
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The gensets are CAT prime movers and leroy somers generators and both the same. I have tried with a bigger load, with the bow thruster the current jumped to 400A on each genset, then one of the gensets went out of sync with that much load,

they do have the proper gear for syncing too..but the boat is from singapore,

i have set the voltages at 425V across each phase on both gensets,

how exactly has droop got to do with this?? might be stupid asking but i thought droop is just for your + or - for voltage
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Old 06-03-2012, 07:56 PM   #12
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Has the system ever worked properly?

Assuming it has not, the first thing I'd check is the CTs.

There will be a CT on each of the 3 phases, plus one more on B.

Check the polarity marking of the extra CTs on B phase. The dot must point toward the gen, not the load.

Also, check the polarity of the secondary of the CTs. These are the two small wires that go to the regulators. They're often black and while, or they could have some sort of other marking on them.

These wires must go to the same terminal numbers on each regulator.

It's also possible that the system uses cross-current for droop compensation. In this case, there'll be two wires that go from one regulator to the other. These must go to opposite terminals (hence the term 'cross-current')

Make sure that the CTs are on B phase. Trace it out and make sure that B is B throughout the system. If the two CTs are on different phases, or the polarity on one of them is opposite of the other, the system will behave like you describe.

Also, check for an open CT. While the system in not in operation, simply lift one of the CT secondary leads anywhere in the system, and measure resistance across the lead and the terminal. It needs to be very close to 0 Ω.

You likely already know this, but I'll say it anyway......never open the secondary circuit of a CT when there's current flowing in the primary. Not even for an instant.

If the regulators have a droop setting, it should be somewhere around 6%, or even more. Both settings must be the same.

If the system worked properly at one time and has failed, I'd look at a shorted or open CT, or maybe the CT shorting switch has failed and is always closed. (It's often a breaker contact.)

If the system was once ok, but has been worked on, one or both of the CTs could have been reinstalled backward, or even on a different phase.

Sorry for the long post, paralleling generators is more complex that simply synching them together.
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