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Old 12-09-2007, 10:59 PM   #1
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I have a question in relation to electrical generators, 240VAC 50 Hz. A colleague wants to run a piece of gear that draws around 10A @240VAC with a pf of 0.8. He has indicated that running two 2kVA generators in parallel will provide greater ampage output, thus allowing the equipment with power draw greater than the output of a single 2kVA (I estimate 6.6A @ pf of 0.8) plant to be run.
My first thought is OMG, what about the phases of each, are they in sync?
Am I off track and there is no problem? If there is a problem what will be effected, the equipment being run (designed for 240VAC 50Hz) or the generators? My gut is telling me that there is a problem and that it will most likely damage the generators. Your help is great appreciated.
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Old 12-10-2007, 02:58 AM   #2
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It's not real complicated, but you can really get things all messed up if the generators are not set up right. You either need to buy the right generators (that are designed to be run in parallel) or DIY. To DIY you need to be able to control the speed of the generators and have governors on the generators that will keep them at the set speed. Being able to maintain speed will help them properly share the load, other wise the generators will fight each other.
For such a small load I would buy a larger generator to avoid the hassle of trying to synchronize the generators.
It can be done , but is it worth the hassle?
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Old 12-10-2007, 06:54 AM   #3
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Trying to parallel 2 small generators is not worth the effort or time. Connect the neutrals and then connect a multimeter between the two generators and watch the voltage swing from 0-240 VAC. You need a controller to keep these 2 in sync.

Additionally I thing (just an assumption) the copper and steel of 2-4 KW units is close or similar to a single 8 KW.
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Old 12-10-2007, 04:38 PM   #4
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Thanks for the input. The type of generators are the portable ones. Each generator has a power outlet (GPO) to connect the extension lead. He was thinking of making up a cable, via a junction box to power the plant (like a 'Y' extension lead) from two generators.

This would mean that you would plug them in, start both generators (one at a time) and then turn the power circuits on at the running generators (one at a time) and finally start the load. In my mind, once the two machines were running and one is switched on (the other is running but not turned on [GPO is switched off]), you could potentially have two machines of different phases. I would have thought that when you switched the second one on, at that instance you could damage something?? Maybe the generator?
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Old 12-10-2007, 06:38 PM   #5
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Quote:
Originally Posted by Futsal1st View Post
, you could potentially have two machines of different phases. I would have thought that when you switched the second one on, at that instance you could damage something?? Maybe the generator?
Yes it could damage something.
One or both of them would do an alligator roll and shoot out sparks. Get a video camera ready because it would be entertaining.
A few years ago I saw what happens when someone tries to connect a 750 KW mobile generator out of sync to a power station bus. It was not good moment.


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Last edited by John; 12-10-2007 at 07:23 PM. Reason: Spelled "Bus" wrong
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