# synchronising single phase



## quanchai (Jul 13, 2012)

Hi guys 

I am wondering if it is possible to synchronise two single phase generators


Each generator generates 65 amps and runs on 230 volts


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## backstay (Feb 3, 2011)

quanchai said:


> Hi guys
> 
> I am wondering if it is possible to synchronise two single phase generators
> 
> Each generator generates 65 amps and runs on 230 volts


Sure, use a scope and vary one speed to match the other. Every generator in the world is put on line the same way. What works best is to have the generator running slightly faster than what you are syncing to, and throw it in between 10 and 11 o'clock.


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## quanchai (Jul 13, 2012)

Is there any thing that can do that automaticly ?


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## backstay (Feb 3, 2011)

quanchai said:


> Is there any thing that can do that automaticly ?


You would need a phase check relay and then a closing relay. I don't know if they make anything in a single phase all in one relay like that.


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## backstay (Feb 3, 2011)

Plus you need a phase loss protector. Just think if one generator quits, now the windings are going to be a load on the other generator(a low resistance short really).


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## dronai (Apr 11, 2011)

backstay said:


> Sure, use a scope and vary one speed to match the other. Every generator in the world is put on line the same way. What works best is to have the generator running slightly faster than what you are syncing to, and throw it in between 10 and 11 o'clock.


Have you ever done it ?


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## don_resqcapt19 (Jul 18, 2010)

Unless the generators are designed to be operated in parallel, what is going to keep then in sync and what is going to control the load sharing?


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## Bbsound (Dec 16, 2011)

don_resqcapt19 said:


> Unless the generators are designed to be operated in parallel, what is going to keep then in sync and what is going to control the load sharing?


The magnetism holds them in sync. 
Backstay you are correct, but what happens if one engine dies for some reason the generator head will then act like a very inefficient electric motor and spin the dead engine.


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## don_resqcapt19 (Jul 18, 2010)

Bbsound said:


> The magnetism holds them in sync.
> ...


That only works if one is substantially bigger than the other. Two generators close to the same size will fight on load sharing and frequency control unless they were designed for and have control systems to let them operate in parallel.


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## micromind (Aug 11, 2007)

A basic synch-check relay that's installed on a 3ø system uses only two of the 3 phases. I've never synched 1ø generators, but there's no reason you couldn't use a synch-check relay to control a power-operated circuit breaker. 

Once they're in synch, they'll stay in synch. While it can be done, it's not easy to get gens to go out of synch once they're paralleled. Even failure of the prime mover (engine) won't do it. One thing that will though, is introducing a bolted fault to the system.......

As noted, load sharing could be a problem. 3ø ∆ generators of the same size and pitch will usually get along with each other, wyes not as well. I don't know about 1ø gens though. 

A reverse current relay will cause a gen to trip out when the prime mover fails. This can be tricky though, it will also take out a perfectly good gen when the system is lightly loaded.


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## backstay (Feb 3, 2011)

Bbsound said:


> The magnetism holds them in sync.
> Backstay you are correct, but what happens if one engine dies for some reason the generator head will then act like a very inefficient electric motor and spin the dead engine.


Which is why on large generators that connect to the grid have phase loss relays and sync check relays. Way back in school(1980's)(early 80's) we would sync small generators to the grid with a scope.

I worked for a large company that had many generators, both steam and hydro. We tied them to the grid by running them slightly faster than the grid and closed the switch as it was coming up to 12 on the sync scope.


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## nolabama (Oct 3, 2007)

backstay said:


> Which is why on large generators that connect to the grid have phase loss relays and sync check relays. Way back in school(1980's)(early 80's) we would sync small generators to the grid with a scope.
> 
> I worked for a large company that had many generators, both steam and hydro. We tied them to the grid by running them slightly faster than the grid and closed the switch as it was coming up to 12 on the sync scope.



they 'sposed to sync with the grid its an infinite supply so to speak - syncing them together is another animal altogether 

you need to get a bigger genny if your syncing single phase stuff - your gonna damage your gennys IMHO


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## Big John (May 23, 2010)

nolabama said:


> they 'sposed to sync with the grid its an infinite supply so to speak - syncing them together is another animal altogether....


 Agreed. It's called an infinite bus connection and it forces the generator to maintain voltage and frequency.

I've never tried to synch two small generators together. I also think that without a common governor it seems very possible the generators would tend to fight each other. 

-John


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## nolabama (Oct 3, 2007)

All of the army's gensets are supposed to work as sycro units they plug into each other and are designed to run thataway - i keep seeing people from other countries ask about this and i am very intrigued about it - i may get a couple of junk 5500 watt units and figure this out


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## backstay (Feb 3, 2011)

nolabama said:


> they 'sposed to sync with the grid its an infinite supply so to speak - syncing them together is another animal altogether
> 
> you need to get a bigger genny if your syncing single phase stuff - your gonna damage your gennys IMHO


Every once in a while we would sync the US and Canadian grids together. We could only do it at around 5 am through the 6800 volt hydro lines. Once an electrical boss was trying to sync to Canada and he closed the switch at 6 o'clock. That's when we found out the sync check relay had failed. It knocked us offline and we had to black start.


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## micromind (Aug 11, 2007)

How well gens will get along with each other when there's no load sharing relay depends a lot on the type of governor.

If both are electronically governed......trouble. This type of governor is more precise, and even if both governors are set to the same frequency, one will usually be slightly different than the other. The faster one will hog most of the load, the slower one will just sit there and idle......

If one or both are mechanically governed, one will usually hog more of the load, but not nearly as much as if both are electronic.


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## frenchelectrican (Mar 15, 2007)

quanchai said:


> Hi guys
> 
> I am wondering if it is possible to synchronise two single phase generators
> 
> ...


 
It possible and I have done it few time and let me give you a tip.,, This is not a faint of heart on this.

What brand monophase generator you are refering to this ??

I rather use larger monophase or use the triphase generator for this purpose it much safer than try to get two monophase generators on sychronous them up.

The other reason why they are pretty tough to do it due the winding pitch that useally get ya by suprise.

Merci,
Marc


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