Question about using generators

Lets say I have a microwave that needs 4000 watts. I have 2 small generators, each 2500 watts. Is there any way you can link the two together to get 5000 watts so that I could use the microwave?

You need two generators that are designed to load-share. There will typically be a connection between the two generators so that they can monitor each other and regulate their output so that one doesn’t try to take all of the load.

Without proper load-sharing, the tiniest difference in voltage between the two generators will cause the one with the higher voltage level to try to take a significantly larger portion of the load, which will cause it to trip out due to overload. The remaining generator won’t be able to handle the load by itself, so it will trip out as well (note - this assumes that both generators have properly functioning overcurrent breakers).

Most of the smaller generators that I have seen do not have load-sharing capability built into them.

Get a smaller microwave, or a larger generator.

Like engineer said, you wont find any low priced generators designed to be linked

On AC generators Voltage is not the major problem. If the generators are synced together the voltage will stay consistent.

The problem comes first in getting the generators in exactly in phase with each other before connecting them together. After the are running in parallel and a load put on the generators they have to maintain the same exact same speed. If one generator trys to go faster than the other it will feed power back into the second causing a over load and tripping out one generator then the other will trip.

Getting two generators to sync up isn’t that big of a deal, if you know what you are doing.

For simple generators, you can use something fancy like a synchroscope, but all you really need to do is connect a light bulb between the hot outputs of each generator (this assumes that you are connecting their neutrals together first). As the generators go in and out of phase with each other, the light bulb will get dimmer and brighter. When the light bulb is completely off, that’s when the phases are equal, and that’s when you throw the switch to connect them. It helps to get the generators as close in speed as possible, as this will make the phase difference roll slowly. If the light is flickering too fast, there’s no way you’ll be able to get the timing right to throw the switch when it’s off.

If one generator naturally puts out a lower voltage than the other, the generator with the higher voltage will power the other one like a motor. Since the outputs are tied together, there won’t be much of a voltage difference between them, but there will be a very slight voltage difference (wires generally aren’t superconductors). I’m doing a bit of technical nit-picking here. Snnipe 70E is basically correct in that there won’t be a significant voltage difference since one will drive the other. I’m not actually disagreeing with him.

If one generator tries to slow down, since the outputs are synced, the other generator will power it as if it were a motor. So adding and removing power from either generator doesn’t affect the overall speed of the pair much, it just determines how much power each provides.

Generators that are designed to load share will monitor their current outputs and will increase or reduce the mechanical power driving them or adjust their field currents so that they keep their loads matched.

Some of the newer generators are DC generators with an inverter. These will sense the phase on the other generator and will automatically adjust their inverter outputs to sync up, so you don’t need a synchroscope or the high-tech (ahem…) light bulb method to sync them. There is also generally a connection between each generator’s inverter so that they can monitor their current and adjust the loads properly for sharing.

Or, the other way real power networks do it: use a DC interconnect, and run the kiln off an inverter.

Assuming that you mean “generator” in the generic sense meaning specifically an “alternator” without an inbuilt rectifier, you add a rectifier to the output, connect a battery as a regulator, and connect the inverter to the battery.

If the “generators” are DC generators without inbuilt inverters, you don’t need to add a rectification stage, but the inverter may still need a battery on the input to stabalise the input.

If the “generators” come with built-in “grid-connect” inverters, then perhaps you could sync them to another small battery-connected inverter that is not grid connect.

Of course, the first thing your microwaves do is probably rectification, and even non-grid-connect inverters have to get their sync signal from somewhere, so there are several system modificaitons you could probably do if you reeally wanted to.

I’ve just been looking at low cost generators for our cottage. The linking feature isn’t something I’ve been looking for, but I have noticed it’s very common for many generators. Most of the new models (of major brands) I’m looking at offer it. That said, they’re only capable to linking to another of their identical models.

This is one “low-priced” model I’m considering:
http://www.homedepot.com/p/Duracell-2-000-Watt-Gas-Powered-Recoil-Start-Portable-Digital-Inverter-Generator-DG2-0i/206475872

I had no idea Duracell was in the generator business until I started looking last summer. They seem very well priced, especially compared to the Honda and Yamaha I was considering, plus they’re a known quality brand. Does anybody have any opinions or experience with them?

All the hoopla related to syncing your two tiny generators aside, it seems that a 4000 watt microwave is an immense load for a microwave.

Unless cooking half a cow, consider acquiring a smaller microwave. Problem solved.

The Honda motors have been the top tier in generators for some time. Yamaha recently has really stepped up and is taking a bite out of that. They are quieter, lighter and linking is a standard feature on the inverters/generators.

I’ve never seen anyone with a Duracell generator.

My experience with small generators is always someone else’s. My small generator is 7500watt. Every time I think about getting something more portable I decide they are too expensive.

Thanks - I’ve never met anyone with a Duracell either. I only need about 2000W, We have a cottage that’s off-grid, but it only has a couple light fixtures we rarely use, we usually light with oil lamps or candles. We mostly use the generator to power a vacuum to clean up the cottage or boat and to recharge the odd battery pack.

I really want to buy the Honda or Yamaha, but they’re such a huge premium versus everyone else. Every time my hand reaches for my wallet i start to shake. Of course in the end I’ll buy one of them (unless someone gives me a sterling reco for the Duracell)

Are you sure about that 4000 Watts? The one in my kitchen is rated at 1450 and gives a power output of 900.

Assuming you are in the U.S., the most power you can get out of a 15 amp outlet is 1800 watts. Even if you upgrade to a 20 amp outlet you’re still talking 2400 watts max.

We’re definitely not talking about a normal-sized American microwave oven here.

Big commercial microwave ovens used in restaurants are typically 2,000 watts or so, but this isn’t something that you can just plug into your nearest kitchen outlet.

I just used the microwave as an example of a device that exceeds the watts available from a single generator. I was just kind of wondering if there was another device that I could plug both generators into that would magically combine their watts to give me one outlet with the combined wattage.