Generator

[ericmark]

The gen is electronics friendly and variable throttle, which means it is quiet.

Clearly an inverter generator, but wonder about electronics friendly I would have expected most generators to be true sine wave are you saying some inverter generators are simulated sine wave?

I've a cheap petrol genny. Think it's 2.2kW. It won't run our fridge as the inrush for the motor is too great for the genny.

I suspect that does depend on fridge/freezer on Falklands I know local farmer used a 3.5 kVA generator without a problem except for sheering when needed the 12 kVA the 3.5 kVA ran his chest freezer OK. I know using a plug in energy meter which measures max power with both my freezer and fridge/freezer they use less than 70W until the auto defrost cuts in when they used 140W the inverter drive does not really produce a inrush current like the old single phase motors.

I would think today most power supplies in electronic equipment use switch mode regulation and have a very large voltage range and the capacitor in the switch mode supply is unlikely to allow any spikes through to any electronics. So it should not matter is generator is slip ring or rotating diode type both should work equally as well.

The regulator method will affect ability to cope with in-rush. With the simple twin wound field windings one in series and one in parallel some generators would overload and others would loose field if over loaded and output would be lost until power was removed. We had both 3.5 and 7 kVA models using single cylinder Lister and twin cylinder Lister the 7 kVA would burn itself out with over load and the 3.5 kVA would lose field yet basic same design.

Most generators are not that basic and have an AVR to control voltage. Biggest cause of generator failure was bearing failure which caused then the rotator to hit the stator. The problem was the direct drive engine was white metal and generator only had bearing one end and that bearing took a lot of hammer as engine bearing wore. Those with layrub couplings worked far better as less hammer on generator bearings.

But this was Falklands and generators ran at least twice a day for at least 8 hours to keep freezer cold. Everyone used chest freezers normal was generator on 10am to 1pm to cool freezer and allow women to do washing, and then again 6pm to 10pm to allow lights to work. Radios were all 12 volt and batteries would be charged from generator.

My friend had generator in a shed and could pull stop from house bed room but had to go to shed to start it. That way he would always check oil before starting. Some farms had auto start generators built 1950's the generator was the starter motor on the Lister ST1. These were only 1.5 kVA but would still run chest freezer although only a small one. I know my friend wanted one of these old units as he could leave the farm for a few days and it would auto start each time the freezer demanded it to. I was quite impressed it would auto start even with a 40W light bulb.

I remember using one in Swan Inlet to run the radio and there was only one light switch for all rooms. So to have enough power for radio (transmitting at 1 kW) we had to remove all but one bulb.

My old fridge/freezer which was not inverter did show a 10A start load, but when checking others used by family found this varied a lot from 4A to 10A so I would guess the lower ones would run OK. I am sure BAS has a clamp on meter with max setting and can test fridge/freezer first.

 

[ban-all-sheds]

but we (at least, most of us!!) used meths to get them started,

Oh yeah - we used meths. Or perhaps any handy flammable VOC he'd acquired through his work as a printer. Once I graduated to using it, I soon got used to the procedure, and blasé about flameouts, jets of burning liquid shooting out etc.

not petrol - which is an awful lot safer

Ever fancied a petrol fuelled one?

(and I still have at least one in the cellar!).

Can you still buy the prickers?

 

[ban-all-sheds]

I am sure BAS has a clamp on meter

Somewhere. Don't think I've ever used it.

 

[JohnW2]

(and I still have at least one in the cellar!).

Can you still buy the prickers?

I believe so (at least, at the last count) - and certainly the long variants I need for my 'flame-thrower'!

Kind Regards, John

 

[ban-all-sheds]

I used to work with someone who bought a holiday home in Scotland, and a long time ago a previous owner had decided that planting rhododendrons would be the thing to do.

Cue soil and climate conditions to their liking, and decades, possibly a century or so, of not much more attention than complete neglect, and he had a big problem on his hands. Hiring a man with a large digger sorted out a lot of it, but there was still manual work to do, and one day, when he and his wife were "cheerfully" hacking away, he asked what she wanted for Christmas.

"A flame thrower" she said.

Apparently, when the day came, she wasn't exactly thrilled to actually get one all wrapped, ribboned and bowed beneath the tree. Women, eh?

 

[ban-all-sheds]

PLAN B

www.ebay.co.uk/itm/2005-350kva-Scania-Diesel-Generator-/141792644328 and sell lecky to the entire street

 

[ban-all-sheds]

Clearly an inverter generator, but wonder about electronics friendly I would have expected most generators to be true sine wave are you saying some inverter generators are simulated sine wave?

Been doing some research, and apparently some are indeed "modified sine wave". If even that isn't misleading for something like this:



And, wot-a-surprise, it's the cheap-as-chips Chinese jobbies (always an apposite word to use, I feel) where the risk arises. It would be nice if I could afford a Honda, but I can't. so I'm wondering if just AVR would be a better bet, as at least the output from an alternator is going to be a sine wave.

 

[a546345]

All my switch mode PSUs (desktop PCs and lots of smaller wall warts), and the boiler pump were quite buzzy when running from a Honda EC2200 site generator. They did work fine though. What do you want to run from your generator?

 

[ban-all-sheds]

Ideally CH boiler, TV, lighting, F/F.

Not encouraged by your EC2200 experience - it's not an inverter model, so unless I'm wrong about the relationship between circular rotation and sin() the output should have been fine.

 

[a546345]

Also, if you have a UPS, it may not lock to an AVR generator. I had to turn the "mains quality" setting on my APC smart-ups down to "low" before it would sync to the site generator. Even then it would drop out as the loads varied and the generator revs caught up. A cheaper UPS might not sync at all, and might not have the tolerance setting.

Ultimately I decided I was probably not doing the electronics any good with a site generator, so I saved up for the LPG inverter gen.

I also found it surprising how annoying the noise was - I ran it during daylight hours for 3 days during the Christmas power cut a couple of years ago. Because of the heavy snow and power cuts there was much less surrounding road noise, and general outside noise that would normally mask the generator sound. I felt obliged to turn it off as it got dark to give the neighbours some relief... I did offer them an extension lead for their fridge and boiler - something else to maybe consider in your loadings...!

Another option could be to get an ex-IT server room on-line UPS which will clean up the generator signal for you.

 

[JohnW2]

Ideally CH boiler, TV, lighting, F/F.

As has been discussed, the F/F is likely to be the biggest problem, since many a small genny can't cope with inrush current of a F/F compressor. Even though, as you say, any alternator should provide a sine wave output, I doubt whether many of the other things you mention are, in reality, all that fussy about waveform, anyway.

In any event, I've never even dreamed of trying to run a freezer off my genny, since I see no real need. An unopened freezer should be fine for 24-48 hours, and I can't recall personally experiencing a power cut of that duration ever in the past 60+ years! My genny is just for CH, a little lighting, modems/routers (useful until the laptop/ 'mobile device' batteries go flat!), and then luxuries like TV etc!

Kind Regards, John

 

[ericmark]

I have used one of the plug in power monitors on my fridge/freezer and freezer and the old one took quite an inrush around 10A and it would need quite a large generator, however new ones don't seem to have an inrush they are both inverter models and it was very easy to see when the de-frost cut in. Run watts was around 60 and defrost watts around 120. I think they use three phase motors?

The odd thing is all freezers would say do not use an extension lead because of the volt drop on start and new inverter still says don't use extension leads but no idea why. On the Falklands chest freezers only were used, and these would work from 3 kVA Lister engine generators.

As to simulated sine wave used a 3kVA with 6 kVA peak inverter in the narrow boat nothing failed to work with simulated sine wave. However we had to select an inverter drive washing machine all other types stated simulated sine wave would be a problem.

Since any switch mode power supply or inverter drive turns all power to DC then back to AC there should not be a problem with simulated sine wave with any units using that technology. The real problem with the simulated sine wave is the poor quality of the inverters that produce it. We found the large inverter we had used car type blade fuses to both protect each FET and to help power share with the resistance of the fuse. The problem was there was no indication when a FET or fuse failed so as time went on more and more fuses would rupture until the load on remaining FET's was too high and blue smoke was released.

So for a small 150W inverter likely with a single FET simulated sine wave is OK. Runs my lap top without a problem. But with the larger units simulated sine wave means low build quality so most narrow boat users have true sine wave as the units are better made and last longer, not because things don't run with simulated sine wave.

With direct AC generators you have to consider the droop with a good quality governor you can get it down to 1% with RR Eagle engines but the speed of the governor correction was so fast it caused the fan belts to slap and we had to have specials made 5 belts in one to stop them failing. I don't think anyone on design thought that using the special governor would cause problems with fan belts. But clearly the very good governor does cause more stress to the engine. Our standard generators had around 7% droop some were up to 15% droop and for me the higher droop was good as easier to keep generators load sharing although for you it would not matter as only using one generator. But the droop does affect things like freezers and I know again on the Falklands using Lister diesel with very large flywheels even a 1.5 kVA generator would run them but try using a petrol generator of same size and they failed due to the droop rather than volt drop.

Volt drop is another problem using a direct field and slip rings an AVR can keep the voltage very stable although the AVR has to control a high current so normally slip ring generators don't use an AVR. With brush less generators the speed of voltage correction is slow, first the AVR increases the current to the static field this in turn produces more current in the armature which is rectified with the revolving diodes to the rotating field which finally increases the output from the stator. It takes some time for the magnetic flux to build up and then the engine starts to slow down so AVR then tries to compensate for engine droop so there is a significant volt drop as the load changes.

In general the bigger the physical size (not kVA output) the better the volt drop and droop. Narrow boat and caravan uses tend not to have freezers and use a very inefficient type of fridge which have no motors. There has been a move to using 12 volt compressor fridges with a power pack to allow 230 volt use as well. Mainly as gas fridges need vents underneath and drilling vent hole in the hull of the boat just does not work. But even the compressor type are very inefficient plus really expensive. I am sure if narrow boat users could run freezers off inverters they would do as they would use less power than 12 volt versions plus a lot cheaper.

I would be interested what Samsung would say about running their inverter fridge/freezer off a simulated sine wave? They are rather new and maybe boat and caravan users will in the future use a standard house type inverter drive unit and step up rather than special 12 volt version and step down when using 230 volt? The efficiency would be far far better as 12 volt D rated and 230 volt A++ rated to start with.

Clearly if you can't afford a inverter generator neither can you afford inverter fridge/freezer. Since power cuts normally are in the Winter fridge is not a problem just need a meat safe outside. Freezer however is a problem and cheap way out is use a chest freezer. Upright freezer will keep food cold enough with out opening doors for around 8 hours after that point it depends what is in it with out inverter freezer on power up we get reading as to temperature so we would know but most don't show temperature so it's a cross your fingers job. The Chest freezer however will keep food frozen for more like 24 hours and you can open lid and remove food required and still last the 8 hours until generator fires up again as found in the Falklands. Since the chest freezers do not auto defrost there is no chance of the power failing just after the de-frost cycle.

When my Beko freezer failed I had a spare freezer so switched on spare and waited a couple of hours for it to cool before transferring food. I had heard the motor fail so knew what time it had failed. So transferring around 4 hours after it failed. It was full and spare one was smaller so knew I would have to get rid of some stuff. However found stuff in top of freezer had already defrosted. So much for 8 hours this was only 4 hours. Stuff in bottom was frozen solid but not stuff in the top.

 

[ban-all-sheds]

In any event, I've never even dreamed of trying to run a freezer off my genny, since I see no real need. An unopened freezer should be fine for 24-48 hours, and I can't recall personally experiencing a power cut of that duration ever in the past 60+ years!

That's true, but possibly a little less true for the fridge part.

 

[ban-all-sheds]

As to simulated sine wave used a 3kVA with 6 kVA peak inverter in the narrow boat nothing failed to work with simulated sine wave. However we had to select an inverter drive washing machine all other types stated simulated sine wave would be a problem.

It's either a sine wave or it's not.

Since any switch mode power supply or inverter drive turns all power to DC then back to AC there should not be a problem with simulated sine wave with any units using that technology.

Come on, Eric - you know that's simply untrue. Many cheap inverters put out something which barely resembles a sine wave. And therein lies the problem. Kipors may look just like Hondas, and indeed they once used to manufacture for Honda, but an easy way for a maker to get the price down is to stick a cheaper inverter in, as that requires no engineering changes at all. And I note that there are quite a few people selling spare Kipor inverters on eBay.

Clearly if you can't afford a inverter generator neither can you afford inverter fridge/freezer.

I can't afford £2K for a good inverter generator.

IHNI whether I could afford the £Δ for an inverter F/F vs traditional, but I won't know that until the day comes when I have to replace mine.

Sadly no room for a chest freezer.

 

[JohnW2]

In any event, I've never even dreamed of trying to run a freezer off my genny, since I see no real need. An unopened freezer should be fine for 24-48 hours, and I can't recall personally experiencing a power cut of that duration ever in the past 60+ years!

That's true, but possibly a little less true for the fridge part.

Indeed - and I suppose that is probably one (a minor one) of the factors that has caused me to steer away from F/Fs. In the event of a power failure, our freezers stay well and truly shut until power has been restored (assuming that happens within a day or two!). As for fridges, the value of the content is usually fairly trivial (and a lot these days in their there only because of labelling, not through true need!), so I'm not too worried about that.

Kind Regards, John