Fridge - mitigate the peak at startup

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Leo Maximus
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Re: Fridge - mitigate the peak at startup




by Leo Maximus » 22/08/18, 10:16

izentrop wrote:
Leo Maximus wrote:We could (maybe) take a toaster resistance.
It is nickel-chromium, temperature coefficient much too low for this function.

For an average fridge of one hundred watts, this NTC should agree
60 ohm at start-up then 1 ohm during operation.

I was joking... :)

I will try to put a wound resistance of a few ohms to see if it can start, and then shunt it. It's not even sure that it works ...

And, supposing that it works on the sector nothing proves that it will work with the inverter.
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Leo Maximus
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Re: Fridge - mitigate the peak at startup




by Leo Maximus » 22/08/18, 10:29

valo wrote:Hello,

My questions are about a solar installation in 24V transformed into 220V by a converter that feeds the house:

I took a long time to finally find a 220V fridge that does not consume much (75W), only here, the peak at startup makes me beep the converter 24 / 220V (4800W), I read that 'at this time the fridge could consume 10 times its nominal value, in my case about 750W, it must I think in the space of a second take too much on the batteries (4 batteries 12V 130AH connected 2 series / 2 parallel so 24V / 260Ah) because once this step, everything works well provided the batteries are full ...

I have read about forum that I could connect a large power bulb in series with my fridge to limit the intensity at startup, so that the compressor starts more slowly and that the peak at startup is acceptable for my installation.

I was going to throw myself into these little jobs today when I thought about something:

If I plug a bulb in series, when starting, the intensity of the fridge should be equal to that of the bulb (since in series we keep the lowest intensity), but once my fridge compressor launched , the bulb that will make it between 100 and 150W (150 / 220 = 0.68A) will then consume more than my fridge that is 75W (75 / 220 = 0.35A), logically, the intensity in my power supply at this time should be that of my fridge is weaker but I am afraid that my bulb causes at this time a surplus of consumption.

Here are my questions:

Has anyone ever tried to connect this bulb or resistance series to his fridge?
Can not I increase the Wh consumption of my fridge by adding this bulb?


So I tried and it does not work. I have provided evidence that what is said about it on the forums is spiel.

I was convinced of it from the start but it had to be experienced.

AMHA, it is much easier to get a 24 volt fridge.

http://uniqueoffgrid.com/fr/wp-content/ ... 5_2017.pdf

https://french.alibaba.com/trade/search ... b=products

Etc. ..

There are some that are in 12/24 volts = plus 230 volts sector!
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izentrop
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Re: Fridge - mitigate the peak at startup




by izentrop » 22/08/18, 11:08

Leo Maximus wrote:So I tried it and it doesn't work. I have provided evidence that what is said about it on the forums is spiel.
You would have a link for them forums in question ?
You say you put 3 60-40 and 75 W bulbs in // but what was the color of the filament? When hot it is around 300 ohm, for 36.4 v at its terminals, the starting resistance of the fridge would therefore be around 54 ohm.

A 1000 W halogen with its hot resistance of 53 ohm should reduce the power at start-up by half and then fade, about 3.5 ohm when cold, but more than that at 0.5 A.
The advantage of NTC, if properly calculated, is that the resistance drops lower in normal operation, causing negligible losses.

The problem is the power supply of this 100/150 W fridge with a 1000 W converter which will trip in the presence of a power call at start-up of 1000 w or more and not with 500 w. : Wink:
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Leo Maximus
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Re: Fridge - mitigate the peak at startup




by Leo Maximus » 22/08/18, 12:42

It is "valo", the initiator of the thread which has the links to the forums. Me, I did not seek. It seems that "valo" has deserted the thread ... : Cry: :)

The color of the filaments? Not having enough to measure Kelvins. I would say on the pifometer that the color was almost normal, "almost" because apparently under-volty. And confirmed by the measurement: 210 volts on the lamps.

I redid a test with coiled resistors of 16 then 10 ohms in place of the lamps.

With 16 ohms, the fridge first clicks-clicks (or clack-clack :) ) for about 2 seconds then it starts normally.

With 10 ohms, the start delay is cut in half.

The resistors are 8 W wound vitrified. They get really hot, of course.

I'm going to see if I have halogens somewhere. Maybe a 250 or 500 W outdoor projector.
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Leo Maximus
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Re: Fridge - mitigate the peak at startup




by Leo Maximus » 22/08/18, 13:12

250 W halogen test:

Resistance measured when cold: 17,5 ohms. Current measured under 235 volts from the 0,93 A sector. This makes 235 W.

The 17,5 ohm resistor is very close to the 16 ohm of the wirewound resistor used previously. It worked.

Test result with the 250 W halogen: no reaction from the fridge. Nothing. The lamp lights up instantly and the lighting is constant.

The NTC solution seems essential to me. With a value = or <16 ohms when cold, the fridge will start. There remains the behavior of the converter ...
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izentrop
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Re: Fridge - mitigate the peak at startup




by izentrop » 22/08/18, 13:47

Leo Maximus wrote:It is "valo", the initiator of the thread which has the links to the forums. Me, I did not seek. It seems that "valo" has deserted the thread ... : Cry: :)
People who believe that everything is theirs and who do not bother to consult the answers of people who go out of their way to find a solution for them. It is incivism.
I redid a test with coiled resistors of 16 then 10 ohms in place of the lamps.

With 16 ohms, the fridge first clicks-clicks (or clack-clack :) ) for about 2 seconds then it starts normally.
With 10 ohms, the start delay is cut in half.
I'm going to see if I have halogens somewhere. Maybe a 250 or 500 W outdoor projector.
Even with a 1000 w halogen it would not start. A fridge compressor starts at full load.

Should be tried with a known resistance of 50 ohm or a little more, so that the motor does not start to determine the value of its resistance at that time and determine the value of NTC most appropriate.
After ...
Leo Maximus wrote:Test result with the 250 W halogen: no reaction from the fridge. Nothing. The lamp lights up instantly and the lighting is constant.
The NTC solution seems essential to me. With a value = or <16 ohms when cold, the fridge will start.
You forget that the halogen lamp is a PTC or CTP in French and that even before starting it will have reached 200 ohm, prohibiting the engine start.
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Leo Maximus
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Re: Fridge - mitigate the peak at startup




by Leo Maximus » 23/08/18, 10:24

izentrop wrote:... You forget that the halogen lamp is a PTC or CTP in French and that even before starting it will have reached 200 ohm, prohibiting the engine start ...

It is very good ... I have not forgotten anything.

It is I who, from my first posts, suggested to "valo" the use of a CTN thermistor. An electric bulb having the characteristics of a PTC thermistor, it is therefore very poorly suited for this use.

But it is not impossible that it works, it is "enough" to find the suitable lamp ... with low voltage lamps, for example.

The lamp is not the right solution but I think it was better to demonstrate it, but "valo" deserted ... : Lol: : Shock:
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Leo Maximus
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Re: Fridge - mitigate the peak at startup




by Leo Maximus » 23/08/18, 13:18

izentrop wrote:.... Even with a 1000 w halogen it would not start. A fridge compressor starts at full load; it will have reached 200 ohm, preventing the motor start ...

Test carried out this afternoon with a halogen 12 volts 50/55 w for the automobile:

The lamp lights strong enough for a short time, due to the overvoltage, then it goes out immediately.

The fridge starts instantly and then works perfectly normally.

I measured 0,42 volts on the lamp with a current of 1,02 amps. It's less than half a watt.

It remains to be seen the behavior with the inverter ... :?:
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izentrop
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Re: Fridge - mitigate the peak at startup




by izentrop » 23/08/18, 15:48

Leo Maximus wrote:Test carried out this afternoon with a halogen 12 volts 50/55 w for the automobile:
The lamp lights strong enough for a short time, due to the overvoltage, then it goes out immediately.
impeccable!
I measured, even putting the 2 filaments in series, I find less than an ohm when cold, normal for it to turn.
A 21 W / 12 V bulb measures 4 ohm cold, it should already be more efficient, see 2 in series
12 V / 5 W even better but it may burn on the first start-up.
Leo Maximus wrote:I measured 0,42 volts on the lamp with a current of 1,02 amps.
About 235 W, it's already a big motor.
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Leo Maximus
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Re: Fridge - mitigate the peak at startup




by Leo Maximus » 23/08/18, 19:48

What is the point of putting the 2 filaments in series?

With a 12V 55W lamp I have within 0,12 ohms when cold (0,28 ohms minus the resistance of the ohmmeter wires), low ohmic values ​​are always difficult to measure. So, not even need a shunt since the fridge does not react a bit when I short-circuit the lamp. It lights up very strongly at start-up but only for a very short time.

I would do a test with a halogen lamp 24 V / 250 watts that has the same resistance to cold. A priori, it is less likely to fuse ... :)

It remains to try with a 24 V = / 230 V ~ converter. I don't have one.
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