Generator or Inverter?

[okrobie]

I'm shopping the "used" market (Craigslist) for a generator or inverter. I'm finding that often, sellers don't know what they have. And, more often I don't know how to distinguish between an inverter and a generator.

For example I looked at a 4KW Briggs & Stratton which had a DC output connector 12V 10 Amp. Does the presence of DC output prove that it is an inverter type?

Thanks, Jim

[wa8yxm]

First an inverter is a box.. No motor, it does not make electricty, it converts the form of the power.

A generator has an engine, It burns fuel of some kind (Sunlight, Gasoline, Propane, Diesel, Wood, Coal, Falling water) and makes electricity.

Reading your original post I think you are talking about a
Traditional Generator or an Inverter GENERATOR

What is the difference?
Regular generators run at a constant speed. some sub multiple of 3600 RPM (3600 RPM 1800 RPM 1200RPM) and the power they generate is delivered. Some of these (epically the 3600RPM types) the power out is... .Kind of nasty (Looks like wholly catapiller on a scope trace)

Inverter genertators can run at most any speed. the power they generate is delivered not to you the user but to a box, called an inverter, which is built into the generator, This box outputs very nice clean power Pure sharp sine wave No "Fuzz" no spikes, sweetest power you will ever use.

And since the motor slows down when the load decreases and for other reasons (They are normally fully enclosed generators) they are fairly quiet.. in fact so quiet that some of the smaller sizes folks have gotten hurt thinking they were not running.. when they were.

You want that kind

How to tell what is being sold
Quick and dirty method.. A @@-####i (note the "i"_) is normally an inverter model

GOOGLE the model number and track it to the maker of the device, They know what they made. You can download the owner's manual there and read it.

[Dano1955]

OK, so i'm getting a 2000w (rated) 2200w (max) generator-inverter. It has 120v outlets and 12v outlet, and a 5a USB outlet. I'm pretty sure this won't power my 15000 BTU AC unit, but this should keep my 2 100w batteries charged and work pretty much everything else (not at the same time) correct?

[DrewE]

Computer power supplies really don't care much about how pure the sine wave is. They're all switching power supplies, so they roughly rectify it into high-voltage DC and then use a chopper circuit and a high-frequency transformer to get the various low voltages required by the computer circuitry.

Many modern computer and other switching power supplies are also not at very sensitive to voltage or frequency differences, as quite often they're designed to work without modification from any mains power supply in the world. That means they need to accept anywhere from nominal 100V to 240V at either 50 or 60 Hz.

Note that this says nothing about how persnickety the UPS may be. It's entirely possible that the UPS was not liking something besides the waveform about your generator power, such as the frequency or the fact that the neutral and ground were not bonded together (assuming it wasn't hooked into the house electrical system via a transfer switch arrangement).

[CJW8]

I've been in power generation my entire career and no generator I know produces a square wave. The physics of how power is produced just won't allow that to happen. There are many things that can affect harmonic distortion as the article states. One thing not mentioned in the article is other loads on the line affecting harmonics. If your power needs are that particular then I'd stick with an inverter generator. I know some ambulances run PSW Xanatrex inverters because they produce very clean power for their sensative medical electronics

The two descriptions above of how inverter generators work are both incorrect. They have an altenator (producing alternating current) at a high voltage that is converted to DC and is then inverted back to AC. Typically they use quality inverters that clean up the power very nicely. Good luck finding one bigger than 3.5KW.

[MrWizard]

there is no such thing as a mechanical driven generator head with square wave output

what you did was buy a cheap generator that did not have an AVR (automatic voltage regulation) for field regulation,
what it did have was a capacitor & diode setup, these are OK for operating motors
but have a nasty spike in the sine wave form when the rotor crosses from one winding to the next reversing the current flow
and your ups which depends on voltage drop sensing to know when to switch to battery power, was totally confused
the switching power supplies in your PC would probably handled it oK
but i don't know WHAT other electronics you are talking about so i can't comment on those

things people fail to realize, is most sensitive electronics aka consumer electronics is NOT so sensitive, not affected by minor voltage variations or electronic noise, ( not like medical equipment measuring minute electrical signals in the body )

and a UPS is to prevent data loss, give shut down time, not protect from power line surges, for that you line conditioning and transient suppression

neither of which is needed with a generator
because a generator is NOT affect by outside interference like lighting on the power pole

IF your generator ever got hit by lighting, you would have a lot more to worry about than your electronics

to sum it up
if your UPS doesn't like the generator power
unplug the UPS, take it out of the circuit and use the generator with out, it is very doubtful that your 'electronics' will be harmed by temporary use of generator power with out the UPS inline

[okrobie]

smkettner wrote:

All non-inverter generators produce a natural sine wave as part of the electromechanical conversion process. Although the wave can get distorted depending on voltage regulation and the type of load. The refrigerator (absorption or compressor) will work fine.

I'm not so sure that is correct. I once had a mission critical computer setup and I bought a contractor grade generator to take care of power outages. I didn't have time to test it out before a power outage came along. I hooked it up to my computers, which were supported by heavy duty UPS's. Well was I ever surprised when the UPS's wouldn't run off of the generator. I was told later that contractor grade generators don't have a clean sine wave, and UPS's need a clean sine wave to operate. Cheap generator output is more like a square wave.

I'm not an RV'r but I came to this forum because you guys and gals are the experts on generators.

I once suffered through a 9 day power outage in the middle of winter in Tulsa Oklahoma. Thus I learned through personal experience that my point of vulnerability was the refrigerator and furnace. I wasn't into computers at the time.

The purpose of my generator will be to provide emergency power for my home during power outages. I want to have enough juice to run my refrigerator, my gas powered furnace and my Ham Radio rig, which includes several computers and UPS's. (Ham Radio is a lot more sophisticated than it used to be). Most of that should run on the generator, but I may have to purify the sine wave for the computer stuff. I can install a small bank of batteries and a Charger/Inverter for that purpose. The Ham Radio gear runs from 12VDC so there will be several options there.

that's where THD applies to electrical power, not just audio. Here is a link to a very good article on THD.
http://powerupgenerator.com/total-harmonic-distortion-portable-generators/ Problem is that it's not always easy to get THD spec's for Portable Generators.

[NinerBikes]

Generally speaking, if the model ends with an "i" in it's name or on the decal on the generator, it's an inverter version.

[DrewE]

Here's my easy (non-scientific) way to tell an inverter generator from a non-inverter generator if you're unsure from the appearance:

Start it up without a load, and analyze what it sounds like. If it sounds like a lawn mower, it's a non-inverter generator. If it sounds like a well-oiled sewing machine, it's an inverter generator.

If it won't start up, it probably doesn't matter which style it is.

This may not entirely apply to larger generators. I've seen some large generators (diesel ones that are their own trailers) that were almost certainly not inverter generators but were very quiet and smooth. They were also more the size you'd need for a small campground, rather than for a single RV.

[time2roll]

okrobie wrote:
Is it safe to run a refrigerator on a plain old contractor grade generator?

Yes. Bring some ear plugs.

All non-inverter generators produce a natural sine wave as part of the electromechanical conversion process. Although the wave can get distorted depending on voltage regulation and the type of load. The refrigerator (absorption or compressor) will work fine.

[MrWizard]

First off
The old style contractor generator with the itty bitty exhaust and chain saw noise, is no longer being sold new in the retail market
Even getting hard to find on the use market, nobody wants them
Even the classic open frame generator being produced and sold harbour freight, champion, B&S etc.. Have a big enough exhaust to keep it down to legal limited on the noise
Inverter generator are just even more quiet
But an inverter generator powering an A/C unit is not super quiet
Super quiet is when it's powering the battery charger or converter and the batteries are taking very low amps, so honda etc.. Is idling in Economy mode

[djousma]

okrobie wrote:
Thank you all for straightening that out for me.

I know that "Quality" Generators have low THD (Total Harmonic Distortion) The ones with low THD can run sensitive electronics and have a prettier shaped sine wave output.

Is there a way to determine the THD of a generator before you buy it. I haven't seen the THD listed in the specs of most generators.

Is it safe to run a refrigerator on a plain old contractor grade generator?

Thanks for your help.

Regards, Jim

Jim,

THD is a term used in the audio (HiFi) industry. what you really care about is the Decible(DB) level. Often you will see the DB rating of a generator. portable non-inverter style generators are generally very inexpensive, and very noisy. The newer inverter style generators are relatively quiet and are available up to about 3500 watts.

[Kayteg1]

I believe all traditional (fixed speed) generators deliver exactly the same kind of power your house has (assuming they are tuned right).
But I don't think anybody will like contractor-grade generator run next to RV.
As already explained, inverter generators use DC alternators and then inverter converts it to 120V AC. Depends on the electronics in inverter the sine can be cleaner more or less.
The advantage of inverter generators is that they can deliver high power when needed for AC start, but once the amps are not needed they lower the speed to actual use, lowering the noise and fuel consumption.
The most popular Honda generators also do have advanced mufflers what makes them extremely quiet. I have Generac inverter generator that is not that quiet, but still beats older (pretty loud) RV Generacs and I like the fuel savings.
My older 4000W Generac was using honest 1 gall of gasoline per hr.
Honda EU3000 will ran 5 hr on the same fuel and load.

[okrobie]

Thank you all for straightening that out for me.

I know that "Quality" Generators have low THD (Total Harmonic Distortion) The ones with low THD can run sensitive electronics and have a prettier shaped sine wave output.

Is there a way to determine the THD of a generator before you buy it. I haven't seen the THD listed in the specs of most generators.

Is it safe to run a refrigerator on a plain old contractor grade generator?

Thanks for your help.

Regards, Jim

[KD4UPL]

The presence of a 12v output has nothing to do with it.
If someone honestly doesn't know if they're selling an inverter gen. or not then they're likely not.
I'm not aware of any inverter gen. larger than about 3,000 watts except Honda and Yamaha. Most inverter generators tend to look all "closed up"; that is, they have side panels and look a lot like a box. The regular type generators are often referred to as open frame. They have a frame with the components mounted to them with lots of room in between where you can "see thru" the machine.
Your best bet is to simply get the model number and look it up online. Any seller that can't give you the model number is not someone I would deal with.