Fridge spike suppression.

ProAsm said:
Yes, you are right and that's why I figure there must be a way to electronically suppress that spike.
Hell it's only for a millisecond or so and with all the technology today we have no solution.
I have a problem with that.
Basically the inverter used to switch off when the fridge came on and I had to go and manually get it going again.
This was a real pain in the butt, so I stripped down the inverter and modified it slightly with a feed back system on the reset transistor (FET).
Problem with this is if there is a genuine serious overload etc it could burn out the inverter.
Well the fridge only trips it once so that works ok, but still the DSTV decoder restarts and you can emagine the flack in the house :)
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https://www.sustainable.co.za/solar-power/solar-fridges.html

Afraid you will likely pay more for the fridge than you would for a bigger inverter.
My 2800kVA Generator gets a bit of pull from my fridge and freezer for around half a second when I flip the switch.
you can hear the motor losing rpm and as soon as the fridge and freezer are running it stabilises.
It struggles a bit more whenever I forget to turn the houses booster pump off before turning the generator on but still runs all 3 :ROFL:
 
Motors and compressors are designed for pure sine wave. None of them perform at all well when confronted with a modified sine wave. hence, as most of the current back up power solutions around are equipped with the modified sine wave, you can expect some very odd behaviour from fridges and A/C units as well as swimming pool pumps.

So now the comparison should be between increasing the capacity of the inverter cost wise and replacing the fridge.
 
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AstroTurf said:
I like that you can run up to 9 in parallel, 21600Watts power should keep any house going :)
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The inverter cost is negligible as compared to the cost of proper batteries, and with that config you looking at a room full of them.
 
Geoff.D said:
Motors and compressors are designed for pure sine wave. None of them perform at all well when confronted with a modified sine wave. hence, as most of the current back up power solutions around are equipped with Modified sine wave, you can expect some very odd behaviour from fridges and A/C units as well as swimming pool pumps.

So now the comparison should be between increasing the capacity of the inverter cost wise and replacing the fridge.
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Yes you quite right.
This is the inverter I have in mind, second to last item at a local dealer and a good price.
http://www.midlandssolar.co.za/product.php?catid=4

The_MAC: at those prices I'll rather get a new inverter + more batteries :)
My batteries are all Silver Calcium and I've had them for 4 years and they still in tip top condition.

First I'm going to try and suppress this spike, somehow, we'll see.
But thanks to all for the comments, it's been very interesting.
 
ProAsm said:
First I'm going to try and suppress this spike, somehow, we'll see.But thanks to all for the comments, it's been very interesting.
Click to expand...

You effectively need a "surge protector" - but if you limit the current, the fridge won't star-up as intended.

Is your fridge in good working condition i.e. clean, not full of ice, door seals in good condition, gas at the right levels etc.
 
Very nice article Arthur, have bookmarked it.
@The_MAC, the fridge was purchased in July 2011 when we bought this house and is still in excellent condition.
Regarding the surge protector, all surge protectors protect the item which is plugged into it.
Basically I need the opposite so what I had in mind is to use a surge protector in reverse.
Hell I got nothing to loose.
Found this on a UK forum:
Surge supressors (aka Voltage dependent resistors) can take the spike out of fridge switching. They should be no more than a couple of pounds from Maplins, and can be fitted across the live and neutral pins in your fridge's plug.
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ProAsm said:
Very nice article Arthur, have bookmarked it.
@The_MAC, the fridge was purchased in July 2011 when we bought this house and is still in excellent condition.
Regarding the surge protector, all surge protectors protect the item which is plugged into it.
Basically I need the opposite so what I had in mind is to use a surge protector in reverse.
Hell I got nothing to loose.
Found this on a UK forum:
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Well not really in reverse, but rather one that is designed for your particular case i.e. a much lower current than the one the surge protector was designed for.
 
You could try a Class III surge protection socket plugged into the wall socket and the Fridge plugged into the Surge Arrestor socket, PROVIDED the surge arrestor can handle the currents posted as per Arthur's reference.
 
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I am not an electrician or power expert in any way, shape or form.

It however seems to me that you are experiencing a brief "brownout" (lack of power) of sort due to the fridge's high inrush current exceeding the inverter's power abilities.

Surge protectors protects against spikes/surges (too much power), so surge protectors will not help, simply limit the amount of power going to the fridge.

If you insist on upping your current modified sine wave inverter, you will need to increase the resistor count/rating and internal capacitor capacity. NOT recommended, but plenty tutorials are available online.

The best solution (in my opinion) is to get a better spec'ed inverter and then maybe later re-add the old/current one to your lighting circuit only (as lights don't really care about a modified sine wave) with a smaller seperate battery setup.

For Example:
1554280633148.png
 
@Geoff.D
Yes I agree as varistors are a lot faster than a VDR.
I'm not too clued up on surge arrestors but are they not directional, dumb question I know, as it's A/C :)
I see these devices are connected between live and neutral, I would have thought between live and earth.

@D4N_CPT
Your diagram is axactly what my aim is.
And yes, brownouts is what we're experiencing when the fridge switches on as the inverter takes 1 second to auto reset with my mod.
I'll see if I can make this auto reset quicker and see how that goes.
I don't mind the lights flickering but the decoder resetting is a problem, although I believe the Explora can run on a 12 volt battery.
Geoff.D, maybe you could comment on that ?
If thats' the case then there is an option open there :)
 
ProAsm said:
@Geoff.D
Yes I agree as varistors are a lot faster than a VDR.
I'm not too clued up on surge arrestors but are they not directional, dumb question I know, as it's A/C :)
I see these devices are connected between live and neutral, I would have thought between live and earth.
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Surge Arrestors are connected between Live and Earth & between Neutral and Earth.

ProAsm said:
@D4N_CPT
Your diagram is axactly what my aim is.
And yes, brownouts is what we're experiencing when the fridge switches on as the inverter takes 1 second to auto reset with my mod.
I'll see if I can make this auto reset quicker and see how that goes.
I don't mind the lights flickering but the decoder resetting is a problem, although I believe the Explora can run on a 12 volt battery.
Geoff.D, maybe you could comment on that ?
If thats' the case then there is an option open there :)
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The above proposal boils down to two back up supplies, one for "dirty power" and the other for "clean power".
Certainly a feasible option, even if on the expensive side.

And yes, all the new DStv decoders are powered with external power supplies, so a direct DC supply to the decoders is possible. Not sure if the supply is 12V as I do not have any of these decoders myself. Should be simple for you to check what the power supply ratings are for the decoders.
 
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Normally I do all my installations myself but this time we bought the Explora on some special which included the installation so I let them get on with it.
Hell I miss my old SD-PVR :crying:
As you say, I'll have a look and if there is a seperate external power supply with whatever DC out then maybe a nice fat 50000 MFD capacitor across it may work for that delay, I do have some here.
 
ProAsm said:
Normally I do all my installations myself but this time we bought the Explora on some special which included the installation so I let them get on with it.
Hell I miss my old SD-PVR :crying:
As you say, I'll have a look and if there is a seperate external power supply with whatever DC out then maybe a nice fat 50000 MFD capacitor across it may work for that delay, I do have some here.
Click to expand...

Ja, I would still have my SD PVR if it did not develop a major fault!
BTW, some of us with the SD PVR still working managed to hack it get rid of all the reboot triggering rubbish! One guy I know has managed to shorten the reboot cycle on his SD PVR to 15 seconds!
 
Thats very interesting indeed.
Any chance of info on how to get rid of the triggering etc.
I still have mine and is still in perfect condition but rebooting drove us crazy, especially during the F1 GP :)
Can email me at 'proasm at gmail dot com' if you have info to share.
Also is there a way to add it to the Explora for dual view ?
I see at the back of my Explora the second RF cable from the dish is not used ?
 
The SD PVR can be combined under XV with an Explora as Primary. No problem there.
It can also be set to use SATCR Universal so will work with a unicable input, but then the Explora needs to be reconfigured.
DStv may be reluctant to do so, but if you press them hard enough they will activate XV on the SD PVR.
Will send you some detail. Which SLNB is installed in the antenna? LMX 500 - 4 Unicable plus 2 Universal; LMX 501 3 unicable and 1 Universal; LMX502Z - 2 Unicable ports?
 
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