Author Topic: Inverter Build Project.  (Read 1811 times)

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Offline welshman

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Re: Inverter Build Project.
« Reply #15 on: October 04, 2020, 05:11:03 pm »
Most of the coupling between the coils will be via the magnetic circuit so I am not sure about whether moving the coils will make much difference.
If it were mine I would put some power onto it and measure the idle current, then move the coils and see if it makes any difference.
The main problem with that sort of transformer will be how much idle current it draws.
Pete

thanks for the input Pete,

As soon as i've got the mosfet bridge up an running for this, ill do exactly that and post the results. As far as i understand the distance between the coils will determine how much flux from the primary reaches the secondary coil/winding. but i guess i'll find our what the practical effects of this are. If i increase the flux, what else do i increase and possibly lose. With this being a backup im not too bothered about the losses.. but as far as im aware, they will be in the region of (only) 10% greater than a toroid.




Offline welshman

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Re: Inverter Build Project.
« Reply #16 on: October 13, 2020, 06:39:36 pm »
more specs on the transformer.

4mm solid copper primary
2x25mm solid copper flat bar wrapped individually for secondary

240v AC In - 58v AC out

i unwound some of the secondary until i got 33v AC out with 230V AC into the primary.

dropping just over 2 volts per wind.

was left with quite a bit of copper.

here is a 48vDC / 33V AC power supply i put together using a microwave transformer keeping the primary and winding a new secondary to give 33v AC from 230 AC input from grid. has a rectifier attached.

most of the parts i need are here now.

Offline welshman

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Re: Inverter Build Project.
« Reply #17 on: October 14, 2020, 06:28:01 am »
i added another turn to the home made power supply secondary, as it was a bit low. AC going in is 237V from the mains. bringing  the output AC volts up to 33.2 and getting 235 V AC on the output of the big transformer.

the no load draw is 80W and i moved the sandwich coils closer together on the transformer but made no difference to the idle current.

is this the idle current loss i can expect when using as an inverter?

next see if adding inductor to the AC primary wire drops the idle current.

Offline Pete

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Re: Inverter Build Project.
« Reply #18 on: October 14, 2020, 05:06:51 pm »
That wattmeter seems to be reading something odd. 32 volts and over 8 amps does not add up to 80 watts.
I have a PowerStar W7 inverter, I added a choke in series with the transformer on it and it did drop the idle current by about half.
My 12 volt 3000 watt powerstar was drawing around 100 watts idle current when I bought it, I managed to get that down to just under 40 watts by adding the choke. As it was my primary inverter it was worth doing.
Pete

Offline welshman

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Re: Inverter Build Project.
« Reply #19 on: October 15, 2020, 07:25:05 am »
That wattmeter seems to be reading something odd. 32 volts and over 8 amps does not add up to 80 watts.
I have a PowerStar W7 inverter, I added a choke in series with the transformer on it and it did drop the idle current by about half.
My 12 volt 3000 watt powerstar was drawing around 100 watts idle current when I bought it, I managed to get that down to just under 40 watts by adding the choke. As it was my primary inverter it was worth doing.
Pete

You are very right Pete, i hadn't noticed.. peacefair pzem016 meter must be faulty.  I'll put a good multimeter in series to see what the real value is.

interesting that your W7 was only 40 watts at idle, that's not a bad loss at all.

Offline welshman

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Re: Inverter Build Project.
« Reply #20 on: October 15, 2020, 08:08:33 am »
I put a multimeter in series and it's showing a no load current of 9 amps. that's almost 300 watts. huge! let's see what a choke/inductor or whatever it actually is, does to the current.

Offline Pete

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Re: Inverter Build Project.
« Reply #21 on: October 15, 2020, 04:50:36 pm »
Maybe the wattmeter was having trouble with the powerfactor. As the coils in the transformer are very highly inductive loads the current would have been lagging the voltage by a long way. So the apparent power and true power are not similar with highly inductive loads.
On our inverters what is drawn on the DC side from the battery is what matters to us, not what a wattmeter reads. Unless we are charging ourselves for the power we use.
Have fun with it
Pete

Offline welshman

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Re: Inverter Build Project.
« Reply #22 on: October 16, 2020, 02:52:40 pm »
Maybe the wattmeter was having trouble with the powerfactor. As the coils in the transformer are very highly inductive loads the current would have been lagging the voltage by a long way. So the apparent power and true power are not similar with highly inductive loads.
On our inverters what is drawn on the DC side from the battery is what matters to us, not what a wattmeter reads. Unless we are charging ourselves for the power we use.
Have fun with it
Pete

it seems you are right Pete. i put a small 300 watt load on it and the readings summed up properly.