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Forum Index : Solar : Solar Hot water system (thanks to forum, Warpspeed and others)
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Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 06:02am 24 Dec 2022
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Mike, I have re wound quite a few toroids, see also my old 'tinker' threads. This was actually quite enjoyable when doing it the easy way. If you read many of my posts you will see it's a learning curve that I, like everybody else went through.
May I suggest you forget about the three stack idea. With a tall narrow 'hole' it's difficult to keep the wire flat against the hole wall as you must to avoid running out of 'hole' space for your primary. A two stack from 2 x 3KW Aerosharp cores is as much inverter as you ever want, it can start and run amazing loads.
These home built inverters have come a long way since 'Oztules' early Power Jack experiments. I have gone along with the new ideas as they came up, the early inverters had a nasty habit of blowing Mosfets for no apparent reasons.
My inverters have now all been updated to the opto isolated version, this has proven soo much more reliable than anything that came before.
Have fun.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 06:58am 24 Dec 2022
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Yes I've read every build post (including your posts) to see what hurdles were overcome by everyone. My main problem is my age and recovering from another recent health setback, it means that doing things like this are a bit tougher.
Fortunately I have the technical skills. I'm going with the OzInverter. I was lucky enough to find one 2.?kW AeroSharp. But I'm using 2 or 3 toriods from the small SMA GTI. The AeroSharp is a similar size but much taller, so 3 x SMA = 2 X AeroSharp.
I plan on starting a build thread (or is might be a help thread?) if I have problems. Just testing the caps and already found issues with one under soak test. If that one had been used in an inverter, it would have eventually destroyed the inverter with any heat built up around the CAP. Next is testing every MOSFET, fortunately I have all the test gear.
Looking forward to the adventure.
Mike. Edited 2022-12-24 16:59 by KeepISIt's all too hard. Mike.
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 08:26am 25 Dec 2022
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Age isn't the problem Mike (I'm 77) but hand and arm strength is. You might get a little fitter winding a decent size toroid. Just take your time. I did all my winding sitting down with plenty of breaks to admire my handiwork .
I would not wind a stacked core if the blank hole was smaller than 90mm. 100mm is much better, especially if you plan to use heavy insulated welding cable for the primary.
Good idea to test the caps, I did leakage tests at their rated voltage and discarded those which were too bad for my liking.
Biggest problem with the 'ozinverter' design is the power board layout, it must have plenty of cooling if one runs it on high power.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 03:35am 26 Dec 2022
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Thanks, I see you found the new thread on the inverter that I started. Fortunately I'm not trying to make it fit into a small cabinet. If I go with the OZ I was planing on changing the layout to make it easier to get at everything, so heat sinking and cap cooling will be revised. Heat is CAP cancer and rapidly destroys CAP life expectancy.
Catch you on the other thread.
Really dull overcast yesterday with drizzling rain, took until 4.30pm for the controller to switch off the HWS thermostat, but it did.It's all too hard. Mike.
Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664
Posted: 08:33pm 02 Jan 2023
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Hi All,
Dropped in this morning with a very similar concept in mind. Presently my Hybrid System is running well under capacity.
Economizing usage has me in a situation where I have at time 1000 to 1500 of Load capacity going unused.
The thought of dropping our HWS off the Ripple Timer control came to mind. Basically, a decent relay/contactor to switch across to the inverter output.
Primary issue though is that it's a 310 Litre HWS with a 3600 element. I'd be wanting to load the inverter down with basically somewhere between 500 & 1500W (AC) depending on conditions.
First thought that comes to mind is SCR/Triac type control like a light dimmer, but have in the back of my mind the fact that my variable heat gun does funny things when I lower it's output when it using inverter power.
Any thought's or previous experience on this approach?
Cheers
Phil.
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135
Posted: 09:41pm 02 Jan 2023
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Does your heat gun use phase control or burst control?
Burst control typically switches the element on / of for up to 10 cycles at a time. Jumping between 0 and max. all the time might be what gives your inverter a hard time.
A Triac triggering after 90 deg. in each half cycle might be less demanding as the inverter never has to supply the full power.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 10:26pm 02 Jan 2023
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There was a discussion somewhere on the worst loads for an inverter (especially with a big Toriod inverter) and some of the crude methods used to change power levels.
My ancient ARLEC heat gun (1.7kW / 2.4kW) causes no issues with the HV (no transformer) pure sine wave inverter. Don't know what it uses to select HI/LO pwr.
The Solar HW controller in this tread is obviously DC in and out and in my case, setup as pulsed DC at all times to keep the loaded output around the MMP of the panels.It's all too hard. Mike.
nickskethisniks Guru Joined: 17/10/2017 Location: BelgiumPosts: 458
Posted: 11:55am 05 Jan 2023
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Phil23
Another solution is make use of a transformer, an autotransformer or rheotor/variac. Or ading An extra heating element.
Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664
Posted: 08:28pm 06 Jan 2023
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Don't know, the heat gun may be an old Ryobi.
2nd element would be nice, but the tank has no facility.
So probably just need a Triac based control that can handle potentially 15A. Would need to be PWM controlled so I can drive it with an ESP for control by Home Assistant.
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024
Posted: 09:48pm 06 Jan 2023
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Phill23, I have used one of those "10000W 25-A High-Power SCR Speed Controller Voltage Regulator Dimmer Thermostat" for soft starting large brush motors, I haven't put a scope on the inverter to see any adverse affects. Probably should start a new topic for this.Cheers Aaron Off The Grid
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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