12 V power inverter does not like powering up Samsung LCD monitors - Page 1
Forum section: electronics / projects

author: Phil P
author_rank: Newbie
timestamp: June 28, 2013, 09:32:52 am
content: I have a 2000W modified sinewave inverter that I have used to power many demanding things like air compressors, jackhammers, drills, etc, but it does not like to power my Samsung LCD monitors.The monitors are 22 inch standard monitors, with inbuilt switchmode power supply (50W when on) . I wonder what the technical issue would be for this inverter to not power them up?I have opened up the monitors, and found a standard SMPSU consisting of some filter components, bridge rectifier and 120uF 450V capacitor. Nothing special, and no active PFC or anything like that.So why would this inverter not want to power them up?The inverter simply loses power when I plug them in. Strangely enough, the overload and overtemp light does not come on. The normal green led just stays on as if everything is OK.....

author: bilko
author_rank: Frequent Contributor
timestamp: June 28, 2013, 09:35:41 am
content: Have you tried to load the inverter with say a 100W light bulb whilst trying to power up the Samsung ?

author: Phil P
author_rank: Newbie
timestamp: June 28, 2013, 09:40:57 am
content: No, what is your reasoning? The inverter doesn't have a standby mode if that is what you are suggesting?I run two compact fluros and a PC ATX power supply, so lots of inductive loads. I still don't see why that would be an issue.

author: bilko
author_rank: Frequent Contributor
timestamp: June 28, 2013, 09:59:43 am
content: There is possibly something that the inverter is doing that the Samsung doesn't like. I thought by trying a base load might eliminate a "quirk", at least if it does then work you will have some more data to consider.

author: Phil P
author_rank: Newbie
timestamp: June 28, 2013, 10:09:30 am
content: I'll give it a go.... Can't hurt!

author: amyk
author_rank: Super Contributor
timestamp: June 28, 2013, 11:19:13 am
content: Quote from: Phil P on June 28, 2013, 09:32:52 amMaybe because its power factor is horribly low, the inverter doesn't like it?

author: Phil P
author_rank: Newbie
timestamp: June 28, 2013, 11:26:04 am
content: I guess so, any ideas on how to correct it? (without buying a new inverter)

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: June 28, 2013, 12:56:39 pm
content: Quote from: Phil P on June 28, 2013, 11:26:04 amTake 30 seconds to try bilkos' sUggestion....then you have some information. After that, we can speculate on how to fix it.

author: SeanB
author_rank: Super Contributor
timestamp: June 28, 2013, 09:10:10 pm
content: Grab a PC power supply with non active power factor correction and wire up the big PFC inductor screwed to the one side of the case to power the monitors. Just make sure you have a real PFC inductor and not the fake ones. The real ones actually have copper wire in the coils and a stacked iron core.

author: Phil P
author_rank: Newbie
timestamp: June 29, 2013, 11:06:32 am
content: Ok I tried it with a 60w bulb and then with two 60w bulbs.It failed both times. Ill try the PFC inductor and go from there.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 29, 2013, 01:47:47 pm
content: Is the output ground directly connected to input ground? Some inverters have a sort of leakage detector, but it is very easy to trigger with noise.

author: Phil P
author_rank: Newbie
timestamp: June 30, 2013, 11:11:35 am
content: Mike, not sure if the mains side is connected to the battery, ill have to check. But I am running an earth leakage detector and it doesn't trip.

author: bilko
author_rank: Frequent Contributor
timestamp: June 30, 2013, 12:08:37 pm
content: Quote from: Phil P on June 28, 2013, 09:32:52 amSorry, I might be a bit dense here. Can you clarify ?Inverter is powered upSamsung LCD is plugged inSamsung LCD is switched onInverter output switches off and stays off ?Am I correct with the above sequence ?Inverter output does not power up again until LCD is disconnected ?

author: Phil P
author_rank: Newbie
timestamp: June 30, 2013, 12:31:30 pm
content: 1. Inverter on2. PC powers on ok3. Plug in 2x monitors and immediately the inverter starts turning on/off at about 2HzIf I turn on the monitors on their own they work until I plug in the PC.So it's definitely narrowing down to a high inductance load issue.Also I can use one monitor and the PC just fine. But the moment all three are connected, in any sequence, the inverter shuts down.I'm surprised at this because as I mentioned, this is a powerful inverter and it has done well with circular saws and high demand power tools, pumps etc. surprised that a mere 250w of inductive load will shut it down. Also surprised the overload light doesn't turn on.

author: bilko
author_rank: Frequent Contributor
timestamp: June 30, 2013, 02:24:58 pm
content: It does sound like the inverter is tripping out on peak power. The inrush current must be taking the inverter monitoring circuit to the limit, even if its for a few milliseconds. Do you have an 1:1 isolation transformer that you can connect to the output of the inverter, so that you can connect the monitors or pc indirectly. The transformer will slow the rise time and round of the MSW a little.

author: Phil P
author_rank: Newbie
timestamp: June 30, 2013, 09:54:16 pm
content: I don't have a 1:1 handy but I do have two beefy transformers that I can join the primaries together on. Ill try it.

author: Phil P
author_rank: Newbie
timestamp: July 07, 2013, 11:40:30 am
content: SUCCESS! I tried the monitors through a 240 to 110v transformer and I couldn't get the inverter to fail. Taking out the inline transformer confirmed the fault again. So yes this sounds like the transformer is making the load less inductive! Hooray, I don't have to buy another inverter!

author: Spunky
author_rank: Regular Contributor
timestamp: July 15, 2013, 12:53:55 am
content: Quote from: Phil P on June 30, 2013, 11:11:35 amBut an ELCB won't work on an inverter anyway unless you install a neutral-earth bond. Small inverters are all floating earth.

author: ptricks
author_rank: Frequent Contributor
timestamp: July 15, 2013, 01:23:42 pm
content: Get a true sine wave inverter if you have the money. Those modified sine wave ( really still square wave) inverters can cause a lot of issues with equipment and equipment that works sometimes will emit a high pitched noise when powered from them.