Auto synchronous generators ? eh!.. practical redundancy

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Auto synchronous generators ? eh!.. practical redundancy

Postby Tracker » Wed Feb 20, 2013 5:50 am

I have to say that motor design and generator design is not something that I can boast about on my CV.. :oops:

Yesterday I saw something that I admit I don't understand .. a new generator being developed, where basic units can be just stacked in parallel and started as the load increases.
There was no electronic circuit controlling motor speeds.. they just connected in parallel... ie .. the equivalent of grid locking of the solar inverter .... KISS.. ;)
Connect two or more in parallel and they just lock and then share the load..

The concept is what excited me.. invest in a small generator today and KNOW that if you make a mistake, you can just buy another... and another as the demand increases.

Best of all.... automatic redundancy for the off-grider... even if it means at reduced capacity..

Redundancy ...... the perceived bane in the lives of the off grid world.. :|

What happens if your 6kw inverter fails, And it take two weeks to repair ..?
How do you cater for all possibilities..? Two three kW inverters rather than one six..?
The house circuits designed with failure in mind... ie essential items on specific circuits, and non essential on others, and then the ability to switch when needed..

Is it that complex, or is it just the case of knowing. "Don't nobody use that bloody dryer - we are on restricted power .." ... :evil:
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby Smurf1976 » Wed Feb 20, 2013 7:55 pm

Large units (as you'd find at power stations) are of course already operated in parallel and have been so for well over a century. Starting them up used to be manual, but certainly for hydro plant it's mostly automatic by remote control these days. That is, a lot of the hydro power stations are literally unmanned and operated by remote control.

Remote control of power stations in Tasmania started in the 1950's and the whole system has automatic stop these days and every plant except one has automatic start too. It's essentially a "point and click" operation these days to start and stop individual machines or for that matter entire power stations.

The one exception, which is 99 years old, still has synchronisation lamps and is started manually - someone has to actually go inside the power station building to start the machines but it can then be left running unattended and stopped remotely if needed. The only reason is hasn't been automated for starting is because doing so would involve adding a lot of clearly visible "modern" components which would spoil the authenticity of it in an historical sense.

I'm not sure what they do in modern thermal (steam) plants however as the only ones I've been in still used the old methods to synchronise machines before putting them online.

As for small units (back on topic.... :D ), Honda already makes generators that can be connected together. Eg you connect 2 x 2 KVA units together and can run a 4 KVA load from them. There's a socket on the generator specifically for this purpose.
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby Tracker » Thu Feb 21, 2013 10:27 am

Smurf1976 wrote:As for small units (back on topic.... :D ), Honda already makes generators that can be connected together. Eg you connect 2 x 2 KVA units together and can run a 4 KVA load from them. There's a socket on the generator specifically for this purpose.

My stupid brain just can't work out how they do it..
I can imagine an electronic controller and especially, an INVERTER run by a generator..

BUT - I am talking about two or more mechanical generators , without control, synchronising "Magnetically", I assume..
The only control is a relay that goes clunk, when the second motor decided that it's synced...
after that they share the load and auto control as one..

It just highlights my lack of deep understanding of how motors/generators really work.
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby Smurf1976 » Thu Feb 21, 2013 6:37 pm

It's just a matter of getting them in phase (unconnected electrically) then connecting them together. Sounds difficult but it's just a matter of speed differential until things line up.

It's a bit like having one car doing 100 km/h on a dead straight road (with no other traffic) following another one doing 99. You have a one km/h difference, and if you have the fast one catch up to the slower one, then drop its' speed back to 99, you could quite easily join them together (by whatever means) just as easily as if they were parked.

Have one alternator at 1500 rpm and other at 1499. Get them to "line up" then bring the speed of both to 1500. Then throw the switch to connect them electrically. Now you're synchronised.

The 99 year old power plant that I was referring to still has a set of both gauges and incandescent light bulbs for synchronising machines with when bringing them online. That's how it always used to be done everywhere. Just line them up at the same speed then connect electrically.

Done manually it's a bit fiddly but doesn't take too long in the hands of an experience operator (I am not such a person by the way).
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby Tracker » Fri Feb 22, 2013 8:04 am

Smurf1976 wrote:It's just a matter of getting them in phase (unconnected electrically) then connecting them together. Sounds difficult but it's just a matter of speed differential until things line up


And, if someone had asked me, that would be the description that I would have used..

As the developer described it to me, these generators do it magnetically. There is NO control system.. they just daisy-chain and auto lock.

Anyway, I will be seeing him again and will seek confirmation .. he is designing these generators specially for off.grid cascading and it's a bit secret at this time.... so, I do suspect that it is a new technique.....
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby offgridQLD » Sun Apr 28, 2013 4:55 pm

I don't see the point in purchasing and maintaining multiple combustion engines driving small generators to do the job of a larger unit.

For off grid application I would say a larger unit running for a short period of time bulk charging the battery bank at a high rate is much better than a smaller unit running all day. The same situation if its used as a emergency back up With the exception that a small unit could be used and just limit the appliances you use. If its a emergency situation (just a few weeks I'm sure not being able to run the dishwasher and iron at the same time wont kill any one ;)

We just pulled out the bathroom in our city house to renovate it. My wife was :shock: what will we do for a shower the next few weeks. Simple a shower tent under the back deck and some hot water in the camping shower. Water runs over the concrete and waters the lawn.

We have all become to soft in the modern age and panic if the electric roller door is out of action for few days :lol: Personally I feel unless your running a business (for example paying guests) or something like better just to make do and down scale in a emergency than over invest.

Water, some lighting, Refrigeration and something to cook on is about all you need. All that can be covered easily with a modest power system or portable generator.

If my inverter needed repairs and was going to take a month than I would just keep things simple for the 4 weeks.


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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby Tracker » Mon Apr 29, 2013 8:51 am

offgridQLD wrote:I don't see the point in purchasing and maintaining multiple combustion engines driving small generators to do the job of a larger unit.


The application was for 110v AC generation ...

I just wonder what the comparative cost would be in considering say three 5kva petrol generators vs one 15kva.

Now I would bet that the 15 would be cheaper than three 5's, but by how much ...???
And when you consider efficiency, is a 5kva more efficient in generating say 4kva, than a 15 generator would be..?
It goes without saying that as AC generators, the redundancy of the three 5 units just has to be a plus, over one 15..

I could liken it to home cooling, where I could have a central unit or multiple zone units like we do.. the clear advantage being that we can efficiently cool the room we need at the time...
Ie. I am confident that a machine working at design capacity will or should be the most efficient..

None of this answers my original concern as to how two generators can just connect and synchronize "magnetically".... all I know is that the suggestion was that the second generator connects to the first for a time until it's in sync and then locks and generates.. my thinking is that the second device acts as a small load to the first, slowing or speeding it up until locked.. all just interesting ...!
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby lithgowlights » Mon May 13, 2013 8:38 am

Smurf1976 wrote:Done manually it's a bit fiddly but doesn't take too long in the hands of an experience operator (I am not such a person by the way).


It's not hard to Synchronise a unit. We don't get a chance too often at work, but enjoy manually synchronizing when possible. Run slightly fast, get synchroscope at a fraction before top and press close on GCB's and you are on and have a very small load. Increase steam flow and you are heading the right way

28 years in power stations, 22 as an operator :)

Multiple smaller generators are good, but overall less efficient when compared to one large unit, but they do offer redundancy if one fails, so you have to weigh up what is needed in terms of backup. In a grid backed system the grid is the backup, but off-grid then you need to think about how long you can go without a generator in worst case situations
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby Tracker » Mon May 13, 2013 11:30 am

thanks for obs'..

as I started, the interest is how a generator can be running and another started in parallel, and they completely LOCK.

I am assuming that the generating one, initially drives the introduced one, and when they LOCK, the EMF keeps them locked.. ie.. if they start to drift, increased current causes them to self adjust such that each motor is supplying the same energy/power..

All just an idle fascination into A/C coupling, that has become such a big topic these days, where two years ago, I had not heard of it..

:D
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Re: Auto synchronous generators ? eh!.. practical redundancy

Postby davidg » Mon May 13, 2013 6:54 pm

Tracker wrote:as I started, the interest is how a generator can be running and another started in parallel, and they completely LOCK.


Keep in mind you are dealing with magnetic fields that are electrically produced, and things work in both directions.

One way to do multi generators, manually without expensive equipment.

A cheap phase sync system manual on is use a say 3 of incandesant lights in series and a voltage meter, common neutral for all generators and a frequency meter per generator.

The lights and volt meters are connected between the actives of the generators (I'll just for this assume single phase generators) When the lights go out, and the volt meter reads zero turn on the interconnect switch between the two actives the 2 generators will now be locked together in phase sync, now it's only a matter of power balance could be 3, 4 or more, phase syncing manually is pretty easy, power balancing is harder. :D
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