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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 964
Posted: 10:44am 04 Mar 2019
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Have a LG front loader washing machine, when running wash cycle it would make the lights flicker just a bit, when running off the High Frequency Inverter. Could see just a little flat top on the sine wave for just a moment. After fitting a ferrite ring around the power lead of the washing machine it seems to settle it down just a bit, well I think its a bit more than my imagination anyway.
The induction cooker is good, barley noticeable with the lights, but not all induction cookers are the same.
Now a real bad one is a Heat Gun of a type, On The HF Inverter It will start on low speed ok but shortly after something in the heat gun switches and it will cause the HF inverter to disconnect the output relay, apparently due to over DC Voltage on the bus, not sure yet. So tried the heat gun on a 2.2Kw generator and starts ok then something starts switching in the heatgun and the little generator don't like it either, High speed setting was ok.
I will try this heat gun on the low frequency inverter later, but first I think I will investigate the guts of this and try and find out why.
I have used Triac/SCR speed controllers on power saws and not had any issues yet.
Have also found that not all inverters behave the same, some HF inverters will run things better than some Low frequency inverters and some the other way round. At least they get the job done.
Anyone else have appliances that cause issues, post here.... And if anyone has found a solution to things like this, it may be of some help to others.Cheers Aaron Off The Grid
poida Guru Joined: 02/02/2017 Location: AustraliaPosts: 1392
Posted: 11:49am 04 Mar 2019
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Revlac, my wife had a hair dryer, that made my smooth running inverter shout out to the world that it wanted to die. We don't have it any more, it failed eventually on mains power and I pulled it apart to see what made it such an ugly load. It was a famous name brand, with off/low/high fan speeds on one switch and cold/warm/hot on another switch. All fan speeds were OK on cold. But use the heat and it seemed to be drawing current on one half AC waveform. The inverter never looked like surviving when I tested it.
Maybe a diode half wave rectifying the heater coil? dunno When I saw it die it was a quick teardown then chuck it in the bin, I could not get it out of the house quick enough. wronger than a phone book full of wrong phone numbers
hotwater Senior Member Joined: 29/08/2017 Location: United StatesPosts: 120
Posted: 02:47pm 04 Mar 2019
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I have a LG washer that will be converted to solar. At least mine only rectifies the peaks of the sine wave and that is where a major surge occurs when the sine wave voltage reaches the voltage of the capacitors. The LG only uses about 300W, but that all occurs in a short time period. This is the difference between watts and VA. Many new appliances are being pushed to use power factor control which makes the load act as a resistor because power companies hate non linear loads.
renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678
Posted: 07:48am 05 Mar 2019
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I remember Oz saying when you first do a fair dinkum test an inverter see if it can run a hairdryer on all settings, if it can then it just passed the test.Cheers Caveman Mark Off grid eastern Melb
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 964
Posted: 10:49am 05 Mar 2019
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poida I opened up the heat gun, and sure enough, on the low speed side of the switch was one diode, so half wave on the heater coil. Not much else in it. Think I will not use it on the inverter's now, not worth blowing up the inverter for it.
Hotwater The LG Washing machine here is about 15yr old and running well, Bit of rust starting. Most power I have seen it use was upto 120W when spin up 800rev's, the lights were flickering on the slow wash cycle, fwd/rev. Like to see how you go converting one to solar.
Mark Some of the older type hair dryer's (no diode) and heaters had 2 coils 2 speed, and would be good for load testing inverters. Best to start by adding more resistive loads without any other interference. Still one old hair dryer kicking around that missed getting thrown out after its user....left. Heat guns and hair dryers they all blowup in the end, usually the nichrome wire burns off.
Another Item, these electric nail and staple guns, these things were bloody terrible on grid power, they would always dim the lights when used. One had a resistor capacitor network, to limit the surge? but not much. Will use the air powered units now. Edited by Revlac 2019-03-06Cheers Aaron Off The Grid
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:49pm 05 Mar 2019
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The rating plate on my refrigerator says running power 127 watts and 320 watts during the defrost cycle, which is just about what I measured.
What I was not expecting was a start up surge of a measured 17 amps peak for the first half cycle quickly falling to the half amp or so average running current one second later. A real eye opener.
A fragile high frequency inverter might have some trouble swallowing that.Cheers, Tony.
renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678
Posted: 02:05am 13 Mar 2019
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Has anyone had problems running inverter type air con on low settings?
My sine turns to crap on this and hair dryer, everything else is fine.Cheers Caveman Mark Off grid eastern Melb
sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251
Posted: 07:14am 13 Mar 2019
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renewableMark,
No issues here with inverter aircons. And howdy do I love em
However my MPPSolar inverter is affected by my 15 year old fridge. The fridge has a ridiculous startup surge and can sometimes cause a flickering effect in linear fluro or LED lights. I solved the LED flicker by replacing the LED PSUs with cheap eBay non-dimable units. The original PSUs were dimmable & would look for the triac chopping in the sine wave. Seemed to happen at lower loads.
Having said that, when I was on grid mains, the same LED lights would sometimes flicker in response to the same fridge or other mains noise. Not as much I suppose due to the grids inherently lower impedance. So I can't blame the inverter.
Come to think of it, I wonder if its worth making an NTC soft starter for it. I think the freezer causes similar problems.
Edited by sPuDd 2019-03-14 It should work ...in theory
Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814
Posted: 08:02pm 13 Mar 2019
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The old 'stick a diode in for low heat' trick... (/Maxwell Smart)
For many years it wasn't allowed to be used in Australia, back when every appliance had to be certified to be allowed to be sold and plugged in (as it imposed a DC element on the AC waveform)
Effectively gives you a pulsed half wave cycle
I used it myself years ago to make a bright/dim setting on my bedside table lamps (made out of Jack Daniels bottles LOL)
Had to fit 'smoothing caps' to them or the bulbs had a noticeable 'flicker' to them (obviously not an issue with a heating element)
I can only imagine what it would do to an inverter with a 2400w heating element going full bore on one half of the waveform and zero draw on the other half Edited by Boppa 2019-03-15
poida Guru Joined: 02/02/2017 Location: AustraliaPosts: 1392
Posted: 03:20am 14 Mar 2019
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At last. For years I have been completely puzzled by this. Years. You have explained what is happening in a way I can grok it.
When I first had an inverter running, I'd load it with a 1/2 wave rectified load from the wife's hair dryer and the inverter would become very unhappy. I never could work out why.
DC loading the transformer's output. All it was.
This is one of those things that I needed to understand but I could never get my head around, so left it and got on with running my house with the solar power.
Thanks so much for this post and the clue, which I needed to finally tie up a loose end.
The next question is how to mitigate DC loading. AC couple the primary? The secondary? Sepic DC-Dc converters use a capacitor to couple the energy from the switch to the LC smoothing net, don't they? Maybe AC couple the 20kHz PWM within the primary..
wronger than a phone book full of wrong phone numbers
Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814
Posted: 07:48am 14 Mar 2019
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Not exactly sure what it would do, whether it is the loading on only half the cycle (one set of mosfet turned on hard, then the next cycle zero draw) - I discovered that my old (1980's vintage Jaycar modified square wave) inverter didn't really care at all, but it had zero control circuitry, it just fed the transformer the waveform and didn't try to correct anything- what came out came out (complete with a high/low switch for when the batteries voltage started to drop!!!- start out on low, and when the output voltage started to drop (tv picture shrunk vertically, lights started to dim, you changed it to high ).... maybe its got the control circuits in a tizzy?
My first sinewave inverter on the other hand had voltage stabilization etc etc, and it HATED my bedside lamps and the ex's hairdrier with a vengeance- lights would flicker throughout the house, the inverter would literally make a varying moaning, humming sound...
Eventually I ended up using both, the mod square for the bathroom and laundry (and my bedside lamps), the sine for the lounge/ bedroom tv's (easy as it was a queenslander on stilts, so I just drilled holes in the floor and passed extension cords through where needed to all plug in the jaycar inverter for its loads, house wiring used for the sinewave (Only reason I got the sine wave one was although it was otherwise perfect, the mod square wave made a VERY audible hum in anything audio and put rolling horizontal lines on the screens of the old CRT tv's of the time)
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 964
Posted: 10:22am 20 Jun 2023
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Ok, time for some boring sinewave pictures, These tests were done on the Old (2015) PIP4048HS inverter (voltronic) First picture, no load just for reference.
Now the load here of 1600w induction cooker running, surprised me that it looked as good or better than no load at all, I was expecting a lot of hash but didn't see any.
Now the dreaded heat gun on low, I have tried running this one on this inverter before and the inverter would shut off the output due to over voltage on the high voltage DC Bus after several seconds then restart and try again. I had never test ed the sinewave when this was happening until now, I was expecting it to have some nasty chopping going on as it did in the little generator. What it did was bulge out just above zero crossing and go progressively larger than in the photo, just too hard to capture it with these limited tools I have.
The next idea was to forget using the low setting on the heat gun and just use the 10Kw scr speed controller to see how that turns out. I connected the speed controller and turned it on, it puts a few spikes on the sinewave at irregular intervals, wound it up till the output was up to 1000w can see some ripple just after the peak of the sinewave, inverter was happy running with this but not sure for how long.
wound it up till the output was up to 1300w can see some ripple just before the peak of the sinewave, sort of makes sense that it would work that way.
Turn the speed controller all the way up and its perfect, the heatgun is just a restive load then, all good. So I think I will just remove the low speed setting from the heat gun and use the speed controller...much more fun.
I know these tests on a low Frequency inverter are going to look a little different but I will get to that on the next build.........Hopefully. Edited 2023-06-20 20:24 by RevlacCheers Aaron Off The Grid
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1401
Posted: 11:05pm 20 Jun 2023
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Hi Aaron, that pretty much agrees with the transformer-Less units I was previously running, I guess the advantage of not having a big inductive toriod ringing like a bell in complaint.
I have a second heat gun with variable heat, but they still have a diode in series on the LO setting, however winding the heat down a little on LO appears to buffers the DC injection/half cycle loading into the AC feed.
FYI, the big (toriod) inverter now only makes a little grunt on the LO setting, but importantly, there's no extra current or nasty spikes appearing on the DC input current waveforms, so it's likely a case of its bark is worse then its bite.... "with the correct chokes".
I also tried some SCR speed controllers recently and they don't appear to bother the Big inverter at all, which is good news. . Edited 2023-06-21 09:07 by KeepISIt's all too hard. Mike.
rustyrotors Newbie Joined: 07/01/2023 Location: United StatesPosts: 32
Posted: 07:14pm 21 Jun 2023
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here is my baseline waveform, running the house with minimal load. 24v 3kw egs002 low freq inverter with 25uH -26 powder iron choke
heatgun on low
microwave. Â whats going on in a microwave that causes so much distortion?
2500W air compressor. i think whats happening here is a large motor load acts like a filter. the motor absorbs anything that is not a perfect sinewave, converting it to heat, and makes the waveform very clean. clean waveform is not due to the inverter build quality, its actually the motor doing all the work here. agree?
Edited 2023-06-22 05:26 by rustyrotors
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1401
Posted: 11:22pm 21 Jun 2023
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Thanks for the DSO screen shots.
The first two show ringing in the toriod caused by the loads, you can improve this by adjusting the choke Inductance down a bit, however you need to be mind full on not compromising the FETS switching current at Idle and low power.
I managed to remove almost all of the ringing and the H-Gun on low looked like that before I lowered the inductance, now it only has a kink, the toriod noise is reduced dramatically. But you are very close to having it right, and at 25uH this might be as good as it gets with this inverter. Â Â Â
I've noticed that with most inverters, placing a big resistive type load results in the cleanest AC waveform. If I drive 4kW of heating elements or a big induction motor, the AC waveform is a copybook sinewave and it was the same at 8.2kW.
I would still suggest that the size of the toriod and the winding ratio will have an effect on the final loaded waveform and noise with bad loads. But obviously the Toriod is dampened by this big resistive loads that swamp the other crap floating around on the AC line. Â Â
I'm still amazed at the silence of this inverter, and I can't even remember the last time a fan started. . Edited 2023-06-22 09:24 by KeepISIt's all too hard. Mike.
analog8484 Regular Member Joined: 11/11/2021 Location: United StatesPosts: 92
Posted: 11:49pm 21 Jun 2023
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Microwave current waveform is large and very non-linear with a significant reactive component. Â So, the inverter voltage waveform is being pull downed and pushed up drastically at different points in every AC cycle. Â That's why the voltage waveform is so distorted.
You can get an inverter microwave to avoid such distortions. Edited 2023-06-22 09:50 by analog8484
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 964
Posted: 08:23am 22 Jun 2023
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I agree Mike, my LF inverter has a wobble in the sinewave with a variable speed drill, but I'm sure that will improve on the next build with better chokes and testing.
@rustyrotors The microwave distortion, I think could be corrected a little with some choke filter adjustment, it should look better than that for an ordinary transformer microwave. I tested the sinewave on with the microwave (old whirlpool 595) running at full power on the HF Inverter and it had 2 small kinks halfway up and down the other side, cant find the picture I took back then, I tried running it today to take another photo but no kinks at all this time it was just a perfect sinewave, just a slight drop in voltage, so I'm sure a good low frequency inverter should run an old microwave without issues.
I can't say much about inverter microwaves, I have heard good and bad things so I don't know till I try one.Cheers Aaron Off The Grid
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1401
Posted: 08:37am 22 Jun 2023
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Aaron, I think I might have mentioned this before, the big Inverter Microwave we have behaves like a dam resistive load powered by my "Wiseguy" Inspired Inverter.
I would never know it's on, and it's one of the highest power units .It's all too hard. Mike.
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 964
Posted: 07:35am 23 Jun 2023
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Looks like I will be putting an Inverter Microwave on my Christmas list, it would probably use half the power that my current (Dinosaur) Microwave uses. 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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).... maybe its got the control circuits in a tizzy?
