Parallelling inverter generators

check out trace or outback inverters websites and maybe send them an e-mail to see if they might help.

Unlike 2-3-4 Synchronous alternators which will lock into one bus,

These Inverter- driven oscillators have no mechanism to see /feel/correct and synchronize their Frequency/phase conditions.

Dangerous even AFTER being synchonized at a particular moment using sophisticated monitoring gear.

Might drift away.Will not know how to remain LOCKED.

Never try to Synchonize and share one LOAD from 2 Inverter-driven Gensets!

HONDA does have a "cable set" which allows these units to run twinned (2 x 3kw= 6kw) but all at the original 110v.

I want to get 3kw @ 110/220v.

So, please let's keep thinking.

This is similar to a "wild leg" not a true " delta", a wild leg voltage can float or vary or may collapse to zero.

There is a transformer that can take single-phase and make it into three phase.

So you are trying to run the two 115v single phases always 180 out of phase to get 220/240 between them. Try putting the two gen sets into a 240 transformer with neutral where each gen set will be "isolated from the other except the neutral, The two phases difference voltage will vary as the generator speed drifts. The load isolation transformer is normally required after an inverter output to limit transients seen/and output of transients by the generator electronics.

Try talking to the gen set manufacturers (Kohler and others) here in WI, there are several they may have built something like the frequency/speed lock-in you are looking for. There is also a company in southern Wisconsin that builds inverters for wind turbines that may have a device like you are looking for.

Normally when synchronizing generators off the grid, they must be tied together at the voltage regulators (droop, etc) as well as matching waveform before closing there breakers.

Generators must normally be 4 to 5 times the KW of any load added to them, for WR2 (rotating mass) for frequency stability, with inverters if the load is too great they will "flat line" and have zero output.

I agree with the idea of not paralleling inverters. But you are trying to get a 180 out of phase, which can't be done by paralleling but by synchronizing 180 out of phase.

Thanks, I'll try the local inverter manufacturers, but just to note, I'm not looking for 220/240 between the two units, I want plain old 120/240v 1 phase to tie into the house during a power outage.

Aeronaut wrote: I'm not looking for 220/240 between the two units, I want plain old 120/240v 1 phase to tie into the house during a power outage.

You can't do it your way with the Honda gensets. Suggest you get the harness that Honda provides to give you plain 120V at twice the amperage. Then use a transformer with 120V in and 120/240 output windings. Cost of such a 6kW transformer is not that much. Plenty of them available in surplus equipment shops.

This is the configuration I normally use on board larger yachts requiring split phase supply. Sometimes older yachts are upgraded with new generators but the cost of completely rewiring the whole boat is too costly.

elnav:

Thanks for the transformer idea, I had not thought of that "simple" approach.

But, keeping that as a later resort, I am still looking for a higher tech lower WEIGHT solution. So far nobody at the manufacturing end has got back to me.

Perhaps soon. Surely this technology cannot be that illusive, and , the solution could be a valuable addition to the stand-by market.

The "aftermarket" has already added remote start to Honda's generators now all we need is VOLTS.

Aeronaut wrote: I am still looking for a higher tech lower WEIGHT solution. So far nobody at the manufacturing end has got back to me.

REPLY

It wil cost you! Victron, to name my favourite brand, makes high frequency switch mode inverters. A 3000 watt unit only weighs 40 lb. You can run them in parallel, up to five for 15kW, or wire them in a three phase configuration to deliver up to 45kW.

I somehow doubt you can find a DC power source big enough to drive such a large inverter bank.

Victron also makes smaller units. However you were talking about two 3kW Honda Gensets so I assume you are looking for about that amount of power. Realistically expect to pay USD $1 per watt for a completed installation. Street price on the Victrons run around $2k for the 3kW units but there are essential extras like cables, battery bank, fuses, switches, etc.

So unless you want to toss money away, run the two Honda's in parallel to give 120V then create your 120/240 center tapped neutral configuration with a transformer to feed your house hold service entrance.

The problem with inverters is the fact you have to recharge the DC source from a prime mover at some point. Then you are back to a motor genset. Unles power outages are frequent and prolonged, you may as well stay with the Honda units.

BTW, you will require an Electrical Code certified transfer switch approved by your local utility authority. Don't even think of doing a DIY lash-up. You will end up killing somebody doing storm repair work on the lines if the transfer switch malfunctions.

There had been a lot of discussion on the suject:

Please see:

Posts:

Paralleling_of_transformers

Paralleling of transformers <http://globalspec.ip09.com/rd/9z1zmpivhik4ta5ahvrd7ji332j9ghv8p0364v3d658> (Electrical Engineering)

&

Combining portable generator output <http://globalspec.ip09.com/rd/9z1z4o4akgbccedogn3ca55c4ivu29tpnsnh7vgo1dg> (Electrical Engineering)

&

Parallel Running of Two Generators <http://globalspec.ip09.com/rd/9z1zvo7amkejrh0q2hq0r49plqc6dub3snuu33qkdtg> (Electrical Engineering)