Transformer selection for DIY LF inverter - Page 1
Forum section: electronics / general

author: phester
author_rank: Contributor
timestamp: September 26, 2018, 08:38:19 pm
content: I am looking at something home brew but as a starting point something like this:https://www.aliexpress.com/item/Aiyima-Pure-Sine-Wave-Power-Frequency-Inverter-Board-12V-24V-36V-48V-60V-600-1000-1500/32873509916.htmlI want to generate enough power to supply my boiler or lights LED (20w) in case we have a grid out of 5 days like during the last hurricane in Ireland. (boiler uses 80W) so even 500W should be enough for the inrush currentusing for example a 24V inverter system I dont know what size transformer I could use. The description says 16V to 220 but I've seen some pictures where as the user has used 220 and 0 out and 15- 0 in. as the above is 500w does this roughly translate to 500va adn this should handle surges above 500va for short times. I am thinking of beginning a thrift search for some old 12V lead acid battery chargers as they may be in the right voltage O/P rangeI would probably go for 24V but if my research is correct I could use the same unit at 12V and the same transformer and get 110 that I could use on my dual voltage appliances such as laptop etc. I think the feedback on this circuit is on the inverter side (LV) and so there may be small change to the circuit EG8010 to make it work.Once I get this far I have 100W of old solar panels and will then buy a cheap pwm charger to keep the batteries topped off

author: f4eru
author_rank: Super Contributor
timestamp: September 28, 2018, 05:02:05 pm
content: QuoteWhy use a sinus inverter for those loads ?Use 24V LEDs, and you probably can get a 24V boiler at a store for "RV" equipment also.

author: fourtytwo42
author_rank: Super Contributor
timestamp: September 28, 2018, 05:52:58 pm
content: Quote from: f4eruI think if you are going to make such statements you should back it up with practical links to assist the OP

author: phester
author_rank: Contributor
timestamp: September 29, 2018, 07:09:54 am
content: No luck in deciding between HR and LF but would still love to go down the project route which tends to be more LF based. When I say boiler I mean the house heating so not going to be installing a LV boiler anytime soonNow my research has thrown up another issue. Neutral and Earth bonding. Most inverters (cheap HF) and as far as I can see the LF homebrew use the Netural as a effective live at half the normal A/C voltage. If you bonded N and E I would have most likely have a buff of smoke on a HF inverter. As the supply is effectively a N and E bonded then a suicide cord would be tuning for smoke. I have saw youtube videos where if you omit the E in your cord then the battery ground floats at half the A/C voltage.Boilers tend to be picky about N and Earth as from what I am reading they use it in the flame detection cct

author: f4eru
author_rank: Super Contributor
timestamp: October 01, 2018, 09:51:28 pm
content: QuoteYep. There's a reason why it's called "Suicide cord"Don't use this dangerous thing. Do proper cabling.Really... Why do the people in US often persist to use this crazy method?

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 01, 2018, 11:02:31 pm
content: I vote for a CHP generator running from whatever heating fuel is available.

author: phester
author_rank: Contributor
timestamp: October 02, 2018, 09:00:59 am
content: Dont get hung up on the suicide part of it. I will be doing a safer method but as its for the one event in (hopefully ) 10 years I wont be investing in a change over panel.I am hoping for hobby help rather that a full retro fit of a heating system.

author: f4eru
author_rank: Super Contributor
timestamp: October 02, 2018, 04:22:38 pm
content: If you do the wiring properly, the ground bonding of the inverter is not a problem, whatever the method the inverter uses internally.

author: Red Squirrel
author_rank: Super Contributor
timestamp: October 14, 2018, 08:09:52 pm
content: Have to watch, some inverters do weird things with the neutral. Instead of the neutral being connected to ground, or being floating, it's actually ground referenced at a non zero voltage. In a typical electrical installation the neutral and ground are normally tied together. You can't do that with an inverter. For a backup setup I would probably just ignore the inverter's ground, as the actual house ground is still going to be a real ground even when the power is out, so you won't really lose any safety. For a permanent setup, like off grid solar, then you can probably connect the ground and simply omit the neutral bonding. Not sure how it's done in professional setups though. Maybe the bigger inverters don't do the weird stuff so it's less of an issue maybe. Some bigger inverters will also do 120/240 so I imagine those might be wired better to easily connect to a normal electrical panel, ground and all. But you want to measure everything first. This is not really something they advertise, you kind of find out once you take it out of the box and test it.

author: f4eru
author_rank: Super Contributor
timestamp: October 15, 2018, 02:28:09 am
content: Yes, some inverters have a DC component between ground and "neutral"But that's OK,When you connect them, you have to disconnect the house neutral from the grid one anyway.