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Forum Index : Electronics : inverter strange behaviour running fridge
| Author | Message | ||||
| stockleys Regular Member  Joined: 21/06/2019 Location: United KingdomPosts: 54 |
evening all some of you may remember me and my head ach of trying to repair my 3000w hf inverter. well, a few months on, and its still going strong. well sort off. i have been having problems with running my fridge from it. it will run the fridge fine, but if i have either of our 2 televisions switch on, when the fridge starts, the invert shuts off. BUT and this is a big but, only if the batteries are above 13.7v 13.8v? sometimes its fine. any higher, not a chance. now i have deduced its not the egs002. as the light goes out completely. then about 5 seconds later, it fades back in at the same time as the transformers start to humm. the only component left that could be causing it, is the pwm board that drives the transformers. now its high shut off voltage is supposedly 15v. i have not tried this. the inverter is rated at 3000w (i have never pulled more than 2600w) both tvs draw around 120w each (we never have them both on at the same time) the fridge draws 72w with a surge of around 1000w. i can start and run my 900w water pump at the same time as the tv, but not the 70w fridge. what gives? any idea whats going on? is there a generic pwm push pull board i could use in place of the current one? thanks in advance for the advice |
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| noneyabussiness Guru  Joined: 31/07/2017 Location: AustraliaPosts: 506 |
Try increasing the high voltage capacitor value, start off small, and include a decent inductor between the output of the push pull high voltage output and the high voltage storage caps.. it will soften the blow and smooth out the current draw.. Unsure of the type/design of your current setup, others will help you better with actual values. Hf inverters can work well as long as designed properly and used within specs.. I think it works !! |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 506 |
tl494 board Very common push pull board. May not be yours though. I think it works !! |
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| stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54 |
that look just like my board, only mine has a 3 pin header for a voltage readout and a buzzer mounted to it. without going out now and opening the inverter, i believe i have 2x 450uf caps from high size dc. would you say up it to 500uf to start? or go 550uf? this is a factory built inverter, so not sure where/how i would mount the inductor |
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| stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54 |
thinking about it, im not sure the caps could be to blame. it will start a 900w pump motor while the tv is on. but it wont start a 70w fridge motor while the tv is on. as an added note, when the tv is on, and the fridge is running, it will quite happily also boil a 2.2kw kettle and not cry about it. seams really strange 900w vs 70w doesnt like the 70w  |
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mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
What would happen if you put a filter inline with the fridge, just an effort to reduce the surge? Mind you modern fridge have crappy electronics in them and may not like a voltage dip. Cheers Andrew |
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renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Some loads are almost like a dead short when they start up, like a drop saw, big angle grinder etc, and compressors. You are simply asking the unit to do what it isn't meant to do. They can't provide a big surge without the transformer like a low frequency unit will. Cheers Caveman Mark Off grid eastern Melb |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 961 |
stockleys, Is it possibly that there might be an inductive spike on the low voltage DC line when the fridge turns on, just a bit higher voltage to cause the inverter to trip on over voltage? Just for curiosity I checked the caps on the 4kw (pip4048) HF inverter I had running the house, 2 caps on the high voltage side at 470uf 500v each, it went ok with that. I guess it depends on how fast the converter side can keep up with the demand and keep those caps charged. Actually 4kw (pip4048) HF inverter did surprise me a few time's what it could handle, had a 551l fridge/freezer a 550l deep freezer and the usual house stuff, then started up 2 550w air-conditioners all good, went round to the inverter and the power box to switch on the breaker for some other appliance? and in the process bumped the main breaker knocking the power out to the whole house, if that wasn't bad enough, without thinking, I just switched the main breaker back on, could hear the fans in the inverter rev up fast, The 2 fridge/freezers stalled and cut out, 1 aircon motor cut out the other one started and continued running. don't know how much power was going through that thing, but thats got to be a hard start. I would try to avoid doing that sort of thing.  Depends on how well these things are built and run within there working limits. Cheers Aaron Off The Grid |
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| stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54 |
what would cause the inductive spike on the dc side? like i say, it will start a 900w (running power) water pump while the tv is on. i find it odd that its just the tv's make a difference. theres never a problem while the tv's are not on (never both at the same time) oh and i can also use my vacuum cleaner (2kw) at the same time as the tv AND the fridge. at any battery voltage. |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 506 |
Most tvs have a dc to dc converter in them, the input caps on them are a virtual dead short when empty, but your output caps should be fine. Just trying ideas here. The 90w fridge compressor may have a " tired " leaky start cap that may be interfering with the TV dc to dc converter causing " noise " back to the inverter, which is simply going nope. Why i suggested what i did, it will help clean up anything coming back. Also make sure it has freewheeling diodes on the low voltage dc side,the inductive noise needs to go somewhere. I think it works !! |
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| tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 430 |
Hi stockleys, To really characterize surge currents of your different loads and their combination, can you scope it using a current shunt resistor? |
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