Put a light bulb between the generators. Once the light goes out they are in sync and you close the switch to combine power. They will stay synchronized based upon load. When one pushes forward it will carry more load and fall back. Not sure how this works on modern equipment but that is how it was done before electronic controls. Would not be surprised if still done today when synchronizing grid generators after a system outage.
Parallel two Generators?
- Thread starter MurphyGuy
- Start date
You don't have a problem with the units staying "synchronized", but load sharing and var sharing is another matter altogether. The little units barely have a voltage regulator, so voltage stability sure as heck isn't going to be there. Actually getting them close to in-sync for long enough to actually parallel them would also be a challenge as I doubt you could do it with load and without load they aren't going to be very consistent.
Today they have PWM control of the field winding and can do var sharing with or without droop compensation wiring.
Warpspeed
Solar Wizard
Basically once electrically connected, the throttle opening controls amps, and the voltage (field winding) controls var.
Being pedantic, the throttle controls kW...
Warpspeed
Solar Wizard
If you are synced and connected to the grid, voltage and frequency hardly changes with throttle, but the current sure does.
DPC
Solar Enthusiast
Trying to think of anyplace I have ever seen done by hand.
And I can't.
They do make relays and there are some simple and fool proof ways to wire things up to do this automatic, without computers and or human intervention.
The reason is if your operator screws up it can be a train wreck.
The MEP generators in a previous post here are militarized version of the Onan DJC and its got a design feature in that slaves the regulator of one to another.
All of this is done automatically to prevent people from screwing it up.
Honda and some other brands of modern inverter generators can be tied together by design.
One should not try and mix and match things that are not specifically designed to.
There are ways it can be done, but that does not mean its a good idea.
If you need a bigger set get one.
If the set you have is too big get a smaller one.
Run one or the other but not both together.
If you read that last line and follow it you will always have one generator that still works waiting in reserve lol....
Opinion:
Buy a good quality inverter generator the right size and use that.
If you spy a good old Kohler, or Onan from days gone past of the saturated field type, exciter cranked and in decent condition ( or bad condition if you like a challenge... I don't know your skill level. ) buy it.
( do you know the value of it though, thats a question in itself, can you evaluate the condition of said equipment yourself )
Buy that iron old timer and keep it as a spare, when your experiments lead to darkness old iron will lead you back into the light.....
Electricity is really dangerous and painful stuff to mess with.
Don't experiment with it.
Know what you are doing, or do not attempt it.
Something to remember a good proper sized generator was chosen to match your needs.
It costs you money but in the long run its worth it.
A bad generator is worth about 15 cents a pound when your done with it.
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DPC
Solar Enthusiast
Yesterday that was done with vacuum tubes and mag amps, and it still did a fine job without fancy electronics.
Onan magneciter.
Very bad idea to try it with one of these or any other system that is not specif in design to do that.
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Warpspeed
Solar Wizard
The original question posed was, how was it done in 1935 before the age of electronics and computers?
Answer with three ordinary light bulbs.
By hand was all there was.
Back then in the 30's, big knife switches with fully exposed high voltage terminals too !
I was in the Antarctic in the early 70's, and I was the radio tech, and backup to the diesel guy that ran the powerhouse. That was equipped with a synchroscope to synchronize and connect up three phase alternators in parallel.
In the vehicle workshop was an old Lister 15kVa that would be put into use if the main power house ever burned down (which has happened).
That still had the ancient three light bulbs method of syncing up to the main power house.
We used to test run it occasionally, sync it up with the light bulbs, and run it in parallel with the main power house, and run it under load for an hour or so.
Rather a lot has changed over the last fifty years. But the old methods do still work.
The only place the younger generations are likely to see any of this is in a museum or a restored historic site.
DPC
Solar Enthusiast
Synchronizing relays have been around that long too.
And I have pulled switches on MG sets the likes of which you describe. ( for PMs and running repairs only )
Some things will never change regardless of the technology around today and tomorrow.
People are too scared to mess with it, especially in the nuclear industry.
Darlington nuclear I am pretty sure is still using a mag amp driven regulator on the pilot exciter.
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Warpspeed
Solar Wizard
RCinFLA
Solar Wizard
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You should not connect two synchronous AC generators in parallel. It can be done if proper sync'g is manually done but other factors, like one generator running out of gas first, makes it impractical. It is highly likely two identical models are not going to be running at exactly the same rpm's. which is the first thing that must match before phasing is matched prior to paralleling. Too many things to go wrong.
For inverter-generator, as previously mentioned, have the first generator started becomes the phase master to which the second generator started follows. Most common user mistake is connecting parallel kit cables AFTER starting both generators.
There used to be actual sync cable but most newer units just have a paralleling kit that has plastic sheathed banana plugs that parallels the two AC outputs together. There are plenty of YouTube videos showing you how to make a double male plug 'suicide' cord to parallel two inverter-generators to avoid paying the price for the manufacturers parallel cable kit. I do not recommend doing this as it is not safe.
If the inverter-generator power combined is such it exceeds the amperage limit of generator AC socket, the parallel kit will have a separate AC socket box capable of the double current of two paralleled inverter-generators.
For inverter-generator, as previously mentioned, have the first generator started becomes the phase master to which the second generator started follows. Most common user mistake is connecting parallel kit cables AFTER starting both generators.
There used to be actual sync cable but most newer units just have a paralleling kit that has plastic sheathed banana plugs that parallels the two AC outputs together. There are plenty of YouTube videos showing you how to make a double male plug 'suicide' cord to parallel two inverter-generators to avoid paying the price for the manufacturers parallel cable kit. I do not recommend doing this as it is not safe.
If the inverter-generator power combined is such it exceeds the amperage limit of generator AC socket, the parallel kit will have a separate AC socket box capable of the double current of two paralleled inverter-generators.
lotsofsparks
New Member
I remember this discussion a Tech collage my Teacher said the larger the phase angle between them the more violent the reaction is when you bring them both online together Meaning that the two sine waves must reach their peak + to together and reach peak - together. If you use some Electrical test lamps across the phases with only the Neutrals connected together then the lamps burn bright the more out of phase it is but If It dims away to nothing and they are at the same Frequency then bringing them online at that moment should be fine in theory at least. fun fact he said someone kept bringing 2 running generators online together without syncing them and the sudden snapping into phase kept on shearing off a 1 ton solid flywheel that spun off passing through brick walls. That's some crazy shit right there.
DPC
Solar Enthusiast
I was working on Ignatrons in some very eldery GE silpacs as late as 2010 in a steel works....
Not sure how its done today but I have seen slip detection systems that used Magamps for that because of fears over reliability of solid state equipment.....
And used into the 90s
Yeah... I got called in on a project where the operator mis-read the synch lights ("bright = go ") and paralleled one generators 180 degrees out of phase to a bank of 3. It flipped the 2MW generator on its end, pulling it from its mounts. The operator was lucky to only get minor injuries (he was in the adjacent switchgear room) from the electrical fault. The entire system had to be written off and the power building required some substantial structural repairs.
lotsofsparks
New Member
How much was the system worth? I would guess they would use PLCs these days to eliminate human error. Some small modern Gensets have a special plug in wire used to parallel 2 of them together. They wouldn't be allow to sell them to the public if it wasn't an automated process.
Hedges
I See Electromagnetic Fields!
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East Coast a few years back, a commuter train barreled into the back of another at full speed. At first they thought it was fault of the new operator lady. Turned out she was standing on the brakes up to moment of impact. Automated system had a relay welded shut.
Automation may not solve all the problems unless people have thought through failure modes.
Checkthisout
Solar Wizard
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The important thing to note is that nothing failed other than the generator mounts.
lotsofsparks
New Member
I'm not a fan of the Automation of planes trains and automobiles. I watched a plane crash investigation on TV where a gyroscope froze into position and the plane ignored the pilot pulling back on the yolk and continued it's nose dive into the ground. The human operator should be able to manually override the automanation at any stage. All the technicians could do is watch nuclear reactor in Fukushima Japan go into meltdown due to the automation system going down. They would have inserted the control rods the moment in went down if there was a manual override system in place.
Checkthisout
Solar Wizard
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The argument goes both ways.
Warpspeed
Solar Wizard
As late as 2000 Westinghouse were still selling locomotive spin slide (traction control) systems that were completely analog, not a microprocessor anywhere. A vast amount of electronics and high speed digital communications systems are used for monitoring the entire rail network, but for the actual direct control of safety critical systems, its still all very conservative.
labeeman
Solar Enthusiast
When it is overloaded.
labeeman
Solar Enthusiast
and even 10's of millions
Warpspeed
Solar Wizard
Oh believe me they do.
I used to be an EE at Westinghouse Brake and Signal in the R&D department. Even a very simple thing goes through a very long and complex process of failure mode analysis, and its almost an impossible task to prove that something cannot fail in a dangerous way.
That is why its so difficult to introduce newer more complex technology.
But there are some basic rules.
Anything must fail in a safe way, usually just stop.
Any fault with the system must give an obvious indication to the operator that something is not right.
For instance, in an aircraft, there are lamps to indicate if the landing gear is actually up or down and locked.
If one of those lamps blows, the pilot knows there is a fault, even if everything else is working properly. No lamp = DANGER.
Engineers think all this right though, and design systems that are as safe as possible, but there is always the unexpected, like faulty maintenance, something gets put back wrong, or a small part is left out. Then there is operator error, and these days unfortunately, deliberate sabotage.
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