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stockleys
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Joined: 21/06/2019
Location: United Kingdom
Posts: 54

Posted: 09:35am 15 Apr 2023

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hi all.
i have succesfully built a working inverter using a chinesse board with an egs002 (mods performed).
i utilised an aerosharp 3kw toroid i left the 230v winding inplace, removing the 250v winding. primary is 35mm, 11turns for 12v (24v lifepo4 battery) (will be upgrading to 50mm)
my inductor is 25uh, rated at 180a. premade from aliexpress.

my idle wattage is 16watts which i am very happy with (old iverter was 103watt(powerstar w7))

my questions are, with the filter cap, i have used a 4.7nf cap, and everything seams fine, but i am unable to check the waveform as my usb scope wont read ac.
would it be a majoy issue if the wavform is not 100%?

i want to wire this inverter to my house using a changeover switch.
how do i go about creating an earth? earth rod a and link to one phase creating a tn-c-s earth?

i have notice that with no load, the toroid has a little noise, but with a 300w resistive load, it goes silent. but a 700w resistive load, it becomes quite noisey. is this normal?

when i put a heavy load on such as the kettle (3kw) my lights pulse. they go every so slightly dimmer for about a second, then back to full brightness. my multi meter is not fast enough to read any voltage fluctuation. but unlike the w7, the lights dont dimm masivly as soon as the kettle is switched on. thw w7 would drop from 235v to 219v with the kettle running. my home brew inverter shows a rock steady voltage of 225v what ever load i put on. (althought lights pulsing) what could be causing the pulsing?

hy4008w, what realistic current can these handle in a bank of 6? (board has 24 total)
i have had 4100w (165amps at 24v) run through the inverter and it didnt grumble.

thanks in advance
Edited 2023-04-15 19:40 by stockleys

mab1
Senior Member

Joined: 10/02/2015
Location: United Kingdom
Posts: 209

Posted: 09:32pm 16 Apr 2023

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Hi Stockley, as I'm somewhat behind you in terms of my inverter build i probably can't offer much advice there.

As for earthing and the neutral-earth bond: well your installation should be compliant with you local regs, but here (uk), you would need to link one side of the inverter output to earth to make a neutral. If your inverter board uses an isolation transformer for voltage feedback then it shouldn't matter which side you choose, but if it uses a non isolating voltage divider(not sure this is a common thing but i have heard of it), then one side would already be tied to battery-ve (probably) and that would need to be the side thats neutral.

I assume you're using a double pole changeover switch. Your neutral earth bond must be on the inverter side of the changeover switch, and should be upstream of any fuses/circuit breakers - ideally at the inverter itself.

As for the earth, that can stay connected to the grid earth, but you also need your own earth rod(s), so that you're not dependent on the grid earth. Your earth rod(s) should have max resistance to earth of 200ohms, and even then you would need RCD protection of all circuits including distribution circuits.
Edited 2023-04-17 07:33 by mab1

noneyabussiness
Guru

Joined: 31/07/2017
Location: Australia
Posts: 512

Posted: 09:59pm 16 Apr 2023

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Oz tested it years ago, 1 hy4008 per leg of h bridge ( 4 total) would comfortably do 2kw all day at 48v ( so 24v half that) with no fan...with a fan it increases exponentially..

thats with " standard " heatsink " on our boards..

I think it works !!

Madness

Guru

Joined: 08/10/2011
Location: Australia
Posts: 2498

Posted: 08:22am 22 Apr 2023

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Is it that your USB oscilloscope will not read AC or is it that it will not work with 240VAC?

If the voltage is the issue find a small transformer with a 240V primary and something around 12V secondary. Connect the 240V side to your inverters AC output and then you can connect your scope to the low voltage side of the transformer. This gives you low voltage as well as isolation so you are not going to have any issues with ground.

As for earthing you can ground the DC but in your whole house circuit you must have only one point where neutral is bonded to earth. Having more than one earth point can create a very dangerous situation if you have a lightning strike close to the house. This is due to very large potential differences between 2 ground points even if they are only a meter apart.
Edited 2023-04-22 18:28 by Madness

There are only 10 types of people in the world: those who understand binary, and those who don't.

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