See post #40.The discussion of how to do that is not allowed in this whole website.
See post #40.The discussion of how to do that is not allowed in this whole website.
I go for overkill usually, the freezer does not consume 5KW of course, but it does make a brief huge current draw when the compressor starts so that's a factor. Here in Arizona in the summer the temps often exceed 115F and in the uncooled garage where this freezer is situated it is very hot, the outside of the freezer cabinet will feel very hot to the touch (in cooler months the outside of the cabinet is cool to the touch!).Wow that's a beast.
5KW is a lot of power though does a freezer really need that much power. Maybe for the startup.
The battery does not have the voltage written on it i was wondering what the voltage was.
Is your power outages due to some grid malfunction or do they impose rolling blackouts where you live?
I couldn't agree more.One does not just modify a 1 KW inverter into a 10 KW inverter. For starters, the 0ne KW transformer must be replaced with a 20 KW transformer. Then the transistors need to be replaced with a set of transistors able to switch that 22KW of input power. And the heat sink needs to be able to dissipate 20times as much heat. and this arrangement does not really deliver a true sine wave.
Then the difficult part is the new drive circuit.
And I am still asking what the device is that spins that 5KW generator. Because it will cost quite a bit less to buy a new alternator that provides 20KW oof sine wave power than to create a 20 KW inverter. AND it will be more efficient.
And now I recall that the company that sold generators back then was called "Northern Tool Company", or just "Northern Tool."
That company is still in business and they offer a 9600 watt generator for $1300. not 20 KW, but enough for most homes. Or buy 2 of them.
The generator is listed as requiring 18horsepower to drive it. Easily cheaper than that list of parts near the start of this thread.
Philadelphia streets (power cables running all over the sky, wooden poles everywhere)Power poles is an interesting subject.
But there would be no point.Hi,
As i said previously, just because he wants to build a 20kW inverter does not necessarily mean that he intends to USE it at 20kW.
It is good practice to use an inverter/converter that is rated higher than the load it will normally have to handle. 2x is not unreasonable, both for reliability AND for motor start applications. In fact, for motor start apps it should probably be rated even higher.
So there is the possibility that the inverter will never have to run at 20kW anyway. Heck, it may even run at 5kW most of the time, but i dont think the original poster mentioned that yet.
But there would be no point.
If one is designing a 10kW inverter, then the design would incorporate overloads, probably briefly up to 20kW and a number of minutes at 25% overload.
A 20kW inverter design would allow for brief 40kW and longer 25kW overloads.
A 10kW inverter would need enough silicon to run at 20kW, but would not need enough heatsinking to run continuously at 20kW.
Perhaps threads should close at a certain time after the TS's last post, to prevent us all waffling on about what the TS really intended?
Wow that's one heck of a system.I go for overkill usually, the freezer does not consume 5KW of course, but it does make a brief huge current draw when the compressor starts so that's a factor. Here in Arizona in the summer the temps often exceed 115F and in the uncooled garage where this freezer is situated it is very hot, the outside of the freezer cabinet will feel very hot to the touch (in cooler months the outside of the cabinet is cool to the touch!).
Bear in mind this is for general use too, the main motivation for it was to power anything essential if we lose power so would be that freezer or perhaps other items too.
My 5G and Century Link "modems" are on UPSs so we have internet when power goes.
The battery is 12V I tracked down a place here that's a trade suppler, named Factory Motorparts, they'll do retail if you walk in and ask nicely, battery cost me 90 bucks so I bought four and keep them charged by topping up every couple of months.
Based on its spec (which I think is this) and the DC current draw when running the freezer I estimated a single battery would last perhaps six hours or so.
The outages happen when we get "monsoon" storms, often short but very heavy wind and rain. The US (unlike much or Europe) still runs local power cables along silly little wooden poles and this is a the risk, if these cables were buried underground like they should be, we'd likely never lose power.
That's interesting. When i go to visit my friend in Los Angeles i dont see any poles in the area i go to either. It's amazing what a difference that makes on the feel of the area. It's very beautiful not to see wires all over the place.Philadelphia streets (power cables running all over the sky, wooden poles everywhere)
View attachment 292560
Liverpool streets (cables buried safely underground no poles (except street lights!))
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Liverpool is very much older and has about a third of the area and population of Philadelphia - just sayin...
On the contrary, I have worked in power electronics for 35 years, long enough to know that when designing a product one doesn't simply pluck an overload margin out of the air, one designs the product for the application. If a 10kW inverter is required then simply designing a 20kW inverter is not the answer. One has to examine the application and determine what type of overload could be present, and how long it could last, and design accordingly. The inrush generated by a motor depends on its load. The inrush generated by LED lighting is quite different, as it is generally over within a single mains cycle, being the time to charge a reservoir capacitor - and the inrush can be reduced by starting at mains zero-crossing. The inrush from a transformer load is worsened by switching on at zero crossing.Hi,
Sorry to say, but by those statements you are making it plain to see you never worked in the power supply industry.
Im also not sure if you had done any reading on power supplies and generators when it comes to motor start problems.
If you had experience in this area there would be no way you would ever say "But there would be no point".
There is a point, and it is well known in the industry. Also, 2x is not always enough either.
Also, see post #42.
I must add too that I enjoyed seeing the poles and cables when I arrived and began living in Philly in 2001. It had a quaintness about it that took me back. Wandering around parts of Philly in the summer was very pleasant, sunny, relatively unhurried, many little mom-n-pop stores and obscure businesses.That's interesting. When i go to visit my friend in Los Angeles i dont see any poles in the area i go to either. It's amazing what a difference that makes on the feel of the area. It's very beautiful not to see wires all over the place.
When i see the two photos you supplied it really nails it. The difference is striking and now it seems very nutty that anyone would run wires all over the state like we have here. Everything is visible looks like a evil genius prototyping project. Just look at all the stuff hanging all over the place. Thick wires, thin wires, junction things, big transformers. Wires running through the tree branches. Who started this i wonder
Hello again,On the contrary, I have worked in power electronics for 35 years, long enough to know that when designing a product one doesn't simply pluck an overload margin out of the air, one designs the product for the application. If a 10kW inverter is required then simply designing a 20kW inverter is not the answer. One has to examine the application and determine what type of overload could be present, and how long it could last, and design accordingly. The inrush generated by a motor depends on its load. The inrush generated by LED lighting is quite different, as it is generally over within a single mains cycle, being the time to charge a reservoir capacitor - and the inrush can be reduced by starting at mains zero-crossing. The inrush from a transformer load is worsened by switching on at zero crossing.
It is not necessarily an advantage to overdesign. An inverter with an oversized transformer will consume more power when idling, so much so that on a dull day the output of the solar panels may be totally consumed by the magnetisation current of the transformer.
A further complication arises in emergency lighting where it is necessary for the sub-circuit fuse to be cleared in the event of a fault - it is no use if the inverter goes into overload protection and turns ALL the lights off. That takes a lot of silicon, and thus leads to reduced conduction losses compared to an inverter that doesn't have to clear the sub-circuit fuse.
When I said "there is no point" I was referring to the concept of designing a 20kW inverter to run off a 10kW generator - or did you not read the earlier posts where the size of the generator was specified?
Hi,I must add too that I enjoyed seeing the poles and cables when I arrived and began living in Philly in 2001. It had a quaintness about it that took me back. Wandering around parts of Philly in the summer was very pleasant, sunny, relatively unhurried, many little mom-n-pop stores and obscure businesses.
We very very rarely see "pole pigs" in Britain.
Back then Philly was more serene than Liverpool or London, the UK has become sort of "harsher" over the years, industry has declined hugely compared to when I was a child. I was safe walking around Center City in the evenings in Philly but less safe in London or Liverpool, that might sound odd bit is true.
I think Philly is different now, I left there in 2005 so haven't lived in the city for eighteen years, I get the impression it has become much more dangerous.
I find it fascinating when two experts disagree - perhaps you actually agree and don't know it!Hello again,
When you said there is no point it sounded like you were referring to the general overload operation so it sounded very strange. That makes you sound smarter now
But what kind of 'power' electronics did you work in.
When you now state different applications you didnt make that clear before this.
Yes a resistive load is different. In the previous post i quoted, the load is much different than a simple resistive load. My brother in law long time ago had the same problem when he tried using a gas generator to run a circular saw. The thing could not get the saw running because it was rated for the current the saw normally draws.
An oversized transformer is not an issue when reliability is the main concern. We did a project for a company i remember they ran their main frame computer i think it was in Newark NJ (this was a pretty long time ago). They did not order an inverter that was oversized. The converter, AND their computer power supply, blew up ... twice.
So again we have a different situation that requires a certain design.
But we had a saying in the lab, "Fools load", as a play on words for "Full load". That's because we ALL knew the general idea that you do not order a converter that will have to operate at the full load, you get an oversized one. This doesnt mean it is not tested for loads greater than that, including a short circuit, it just means the reliability has to be there and to get that it is not a good idea to order a converter that will have to operate at the full load on a continuous basis, which many do anyway and end up regretting it.
I wouldnt mind hearing your take on the same ideas but with a UPS system. For a UPS system you dont order a unit that will give you 5 minutes of run time if you need 5 minutes of run time, you order a unit that has at least twice the capacity.
Note in all of the above we didnt even take the manufacturer's honesty into account yet.
It's nice to meet someone who worked in power but it would be interesting to find out what kind of power devices and maybe max power and what you did there.
Thanks for the reply.
Hi,Putting ALL of those wires underground can be a very big deal. I have lived in an area where bedrock was about a foot down, which made strong foundations easy, but it made burying utilities a pain. Then, at another time, I lived in another section of the country where the water table was about two feet below the surface, and when a new section was built with underground electrical lines, there were weekly power problems, both outages and big spikes. The spikes were due to the neutral ground being inadequate, and so when one line phase suffered a grounding fault, the neutral and opposite phases were pulled up much higher. So both light bulbs and tubes suffered burnouts. So there are places where buried utilities do not work well.
Also, upgrading buried electrical distribution lines would be expensive.
Hi,I find it fascinating when two experts disagree - perhaps you actually agree and don't know it!
I live in Oregon, a major producer of wooden power poles.producer
That's interesting. When i go to visit my friend in Los Angeles i dont see any poles in the area i go to either. It's amazing what a difference that makes on the feel of the area. It's very beautiful not to see wires all over the place.
When i see the two photos you supplied it really nails it. The difference is striking and now it seems very nutty that anyone would run wires all over the state like we have here. Everything is visible looks like a evil genius prototyping project. Just look at all the stuff hanging all over the place. Thick wires, thin wires, junction things, big transformers. Wires running through the tree branches. Who started this i wonder
Oh yeah wire size is important too. I found out my OBDII connecter wiring was only AWG26 to AWG24 so i could not charge my car battery through the OBDII port.At acouple of different jobs I was designing the electrical and electronics portions of mostly auto Plant production test systems. The reliability standard was 100% uptime. So no component was ever intended to operate at more than 80% of it's rated capability. Certainly it cost a bit more and it might have used a bit more power. But stopping the line for five minutes one time will eat up that difference in cost. Certainly that is much different from consumer electronics, where the 5 watt resistor is run at 6 watts all the time, and the intended life of some products is a week beyond the warranty period. Most last longer than that, fortunately. Things are a bit better in some areas, fortunately.
And I have had to explain starting load to somebody wanting to run their circular saw from an inverter. They had a 5.1 amp saw and a ten amp inverter, and I had to explain that the battery conections did need to be the size for when the inverter delivered ten amps at 120 volts, and that watts in would be at least the same as watts out. That is good enough for wire sizing to handle the starting current, because it is based on heating, not voltage drop.
by Jake Hertz
by Dale Wilson
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by Jake Hertz