DC to MAINS Inverter experts? - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: June 03, 2019, 05:10:02 pm
content: This is a pretty vague question, here goes......I was told that some (perhaps most) of the newer 120V pure sine wave inverters have load detection schemes that basically keep the inverter output in a low power state disabled state whenever no load is detected by the inverter. In this state the inverter "blips" it's output every so often looking for a load and when a load is detected the inverter then activates the output stage until the load gets switched off.Does this sound correct and if so does anyone have any insight as to how often the "blips" occur, thresholds etc?

author: Bratster
author_rank: Frequent Contributor
timestamp: June 03, 2019, 05:30:11 pm
content: in my experience that's not normally something that's on by default or even universally supported, generally the inverter is continuously outputting.But that is definitely a fairly common option.Usually goes under the name of power save or search mode, something along those lines.especially on the large low frequency transformer style of inverter because their idle current is so high.I think it's less common in the high frequency style of inverter because their idle current can be very low.As far as what it actually is, usually it would be one or two complete cycles of AC, and they could be sent every 1 to 10 seconds depending on the inverter.The nicer ones are configurable as to how often they should search for a load and what the minimum load should be.I'm no expert, but I have installed a handful of low frequency and high frequency inverters with and without that option.Sent from my Pixel 2 XL using Tapatalk

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 03, 2019, 05:41:31 pm
content: A better way it could be done is to send a high frequency pulse and measure the return signal, specifically looking for a significant change as would be caused by a switch changing state.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: June 03, 2019, 05:51:33 pm
content: There are inverters that require a minimum load or otherwise go out of spec (output voltage exceeds nominal output), also some thyristor designs require a method to switch these thyristors off, those might fail without an actual load. The alternative would be to include a dummy load in the design and constantly waste energy to it.But those are kind of old designs, might be that these things are outdated.So regarding the question it depends on the application how often you need to try to detect a load. Once per sine wave might be a good start? Not so often that you go out of spec, but often enough to reliably start operation.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 03, 2019, 08:25:29 pm
content: Gonna sound stupid, what is the gain to have a sleep function, or low power and still running, you know you have a current draw / consumption to make it runA simple power off is enoughyou dont use it kill it ??

author: Bratster
author_rank: Frequent Contributor
timestamp: June 04, 2019, 06:04:40 am
content: Quote from: coromonadalix on June 03, 2019, 08:25:29 pmFor a so-called high frequency inverter, there's not really any benefits since their unloaded power draw is pretty low already.however for the so-called low frequency inverters that have a massive transformer in them, their unloaded power draw can be sometimes as high as 100-300 watts.so it's definitely beneficial to have that kind of inverter essentially shut down until they see a large enough load and then automatically power up.Sent from my Pixel 2 XL using Tapatalk

author: John B
author_rank: Frequent Contributor
timestamp: June 04, 2019, 09:15:17 am
content: I have a low frequency inverter that does what you're describing. There is an adjustment knob to alter the sensitivity, but I don't know if it adjusts the minimum current needed to activate the output, or whether it alters the frequency at which it blips the output. I do remember that at low sensitivity (ie the most power saving mode) it blips the output around once or twice per second.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: June 04, 2019, 10:50:50 am
content: Quote from: Jester on June 03, 2019, 05:10:02 pmYeah I have seen that too, someones inverter didn't turn on after they switched their lights to LEDs.

author: strawberry
author_rank: Super Contributor
timestamp: June 04, 2019, 11:59:20 am
content: some high impedance dc sense voltage is fed in to mains side socket, when load shorts sense signal, then inverter is forced to turn on.TV set could ask inverter that it needs power. there is no such devices by now