Fridge - mitigate the peak at startup

[value]

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?

Something else :

Not having 6mm² cables, I connected my panels to my MPPT and my batteries to my converter with 3G / 2.5 each time putting the 3 wires together to increase the section at each terminal, I know that this is not "up to standard" but are there any downsides to doing so?

[Leo Maximus]

We should be able to shunt the lamp (automatically ...!) Once the compressor is launched.

[value]

Hello !

What do you call "automatically"? You mean it would shut off on its own once the compressor started?
Because the fridge is triggered several times a day, I can not do an action that would shunt the bulb each time ...

[Leo Maximus]

"Automatically", I mean with an electronic relay or triac circuit. It must exist.

You should do a search with the keyword "soft start".

Personally, I would do a test with a lamp and a switch in parallel on the lamp, just to see what a manual "soft start" gives.

And it must be possible to use the electrical circuit of the fridge itself when starting. The lamp being shunted 1 second after starting by a timed relay. It's just an idea like this ...

A thousand excuses, I have to leave ...

[value]

Ok, what would you have tried is like the diagram I attached to you?

I will first try to connect my converter next to my batteries to reduce the cable distance and see if it still beep, after that I'll try the shot of the bulb.

[Leo Maximus]

That's exactly it for the schema.

[Leo Maximus]

I add something: the filament of a conventional tungsten lamp has a positive temperature coefficient. Its resistance is low to cold but it increases with temperature. It is a PTC thermistor.

In the present case it would be necessary the opposite, ie a thermistor with negative temperature coefficient, a CTN (or NTC).

At the start of the fridge the CTN will have a high resistance but it will decrease with heating, gradually approaching 0 ohms, the ideal. It remains to find the right ... a priori NTC thermistor whose cold resistance will be equal to that of cold tungsten lamp (assuming it works with the lamp).

See at RS: https://fr.rs-online.com/web/c/passifs/ ... 4294138050

[izentrop]

Hello,
It is often necessary to oversize an inverter to control inductive loads.

A timed relay. example
If not something to try is a vacuum regulator module variable speed, recovered on a vacuum whose engine is dead.
Even set to maximum, they cause a soft start. I noticed that on big model Hoover or Electrolux.
I have never tried, so no guarantee that it works on a small engine.

[dede2002]

Hello,

Ok with all that was written above, but I would try anyway with another fridge (or other inverter). There may be too much pressure in the compressor at start-up. And so it would start even harder with less tension, if you put a resistance in series ...

The engine power of the fridge is not very important, since it operates intermittently.

Otherwise, for the question of cables no problem 3 x 2.5 = 7.5 mm2.

[Leo Maximus]

That's why I suggested a CTN thermistor rather than a lamp that is a CTP thermistor.

With a proper TNC, we will have the 230V after a short time since the resistance will fall to 0 ohms.

With the lamp, the starting voltage will collapse because there are 2 windings at the start of the fridge: the starter coil and the winding work and there are risks that it does not even start.

In any case, there must be a problem on the side of the converter (output signal) and / or the batteries (internal resistance).