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Author Topic: Chinese Inverters  (Read 4762 times)

listerdiesel

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Chinese Inverters
« on: December 11, 2007, 07:14:30 PM »
As a company, we have a large product range in the battery charger field, and most of our designs are pretty much frozem, albeit very flexible to implement, either in single or three phase supply.

Recently we dug out some old plans for the inverter market, and decided to buy a current production unit to see where everyone was heading in tyerms of design etc.

We bought a pure Sine Wave 1.5kVA continuous unit that ran off 48V, and it arrived today, after a week of chasing the vendor to see where the h*ll it had got to.

Price was about $US 550 plus $US 60 shipping.

I was a joke!  We had a list of problems a mile long within half an hour of opening the box, ranging from bad or scratched paintwork, self-tappers instead of threaded fasteners on the covers where they had reamed out the threads, PCB's on M3 screws and spacers, while the proper fixed pillars went unused (for a different model no doubt) Missing front panel screws.

And so on.

Then we took the thing to pieces....

Damaged tracks on the PCB's, cobbled-up links to get around faults on the wiring, the PIC chip that did all the Sine-Wave generation had had its number sanded off to stop people finding out what it was....  You could still see PIC in the surface under a magnifier and it's about the only chip used by anyone in the game. Cobble together little piles of resistors in place of a single one, and a pot that was somehow jammed in amongst other parts on a couple of bits of wire.

All in all it was a right bl**dy mess.

Contacted the vendor, who passed the complaint back up the line to another person, they said that it had never happened before.....  must have  been a customer return that got sent out again by mistake etc etc.

They are now going to bring a replacement unit to us and collect the old one. I have taken pictures of all the problems, just in case they want to deny it later.

It wasn't a cheap unit, we tried to pitch our buy at a level where we should have got something reasonable to look at, but there you go.

I'll report back on the replacement when I get it.

Peter

listerdiesel

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Re: Chinese Inverters
« Reply #1 on: December 11, 2007, 08:37:40 PM »
Any plans on looking at other manufacturers such as Outback ?

Jens

Not at present, we would want to either buy or licence the software in the chip as we haven't got the time (read 'I' haven't got the time) to get involved in writing the machine code necessary, although TI and a few others have published the basics for generating a waveform digitally, the FET drive etc is pretty standard, nearly always an FET full bridge driving a big iron-cored tranny and a bit of mush filtering on the output.

My youngest son repairs APC UPS's for a friend, and he has a pallet-load of big ones that we hack around and play with. Interesting to see the failures in those, nearly always the bridge power FET's blowing up, usually because the opposing device has held 'on' instead of 'off' - big BANG!

Peter


Doug

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Re: Chinese Inverters
« Reply #2 on: December 11, 2007, 11:34:53 PM »
The GE Silpac uses a 6 phase ( Y-Delta seconday transformer ). We use 24 pulses to gate the valves ( SCR stacks ). Two units run in a master slave arangement. Both master and slave wok together a single 4 quad DC drive .

Every now and them something happens and two or more valves gate that souldn't. If I'm lucky this trips the loop breaker. If I'm not a valve blows, lights flicker and people crap their pants ( since average current on the twins is about 2000 amps at 800 volts )

I hate electronics, even old struff like this because it hates me too..... 

I like FET cheeze on toast with a little fresh tomato and Greak dressing.
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Doug

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Re: Chinese Inverters
« Reply #3 on: December 12, 2007, 12:16:16 AM »
We use two kinds the realy cheap from Canadian tire ( that we beat and drop and abuse ) and the Motomasters seem to last.

We also have some expen sive 3.3 kw pure sign wave inverters ( that the shaft crew charges by smell, uses in damp locations, bumps around on rusty old troleys and best of all they use them to run power tools like hammer drills and lights ). These have been reliable in isnpite of poor work practices.

I wonder of you guys just have bad luck?
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mobile_bob

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Re: Chinese Inverters
« Reply #4 on: December 12, 2007, 01:20:33 AM »
i have used numerous cheap inverters all made in china i am sure
and for the most part they have performed well above expectations,, who knew?

i did however many years ago buy a tripplite pv550,, and what a piece of sh#t!
it died within a week running a desktop puter in the service van, the replacement blew up in less than 5 minutes
and the replacement for that one lasted about a month before someone decided to liberate it from me,,, perhaps it was a good one
but like granny used to say
"maybe so, but i kinda friggin doubt it"

i have heard really good things about outbacks inverters, they seem to work well and the company is second to none in customer support

i have also heard that xantrex has some issues with some of their units, but some folks seem to have excellent luck with them

i can't imagine a 1.5 kwatt pure sine wave at 550 bucks being worth dragging home in my opinion, 550 for a mod square wave (aka mod sine wave)
is probably going to be a fairly good one though.

when it comes to inverters i think i am going with the exeltech ms series rack mounted
the individual inverter module go for about 700 bucks each and are 1 kwatt pure sine wave as well
from what i understand they are an american design built in the good old usa,, the telecom folks seem to like em at least in the 48volt versions that they use.

exeltech makes them in everything from 12volt input to 108volts iirc,, and they will custom configure to whatever voltage one wants to work with i am told.

kind of pricey, time you get the rack , the main processor module and a full load of inverter modules, but they supposedly have a mean time before failure of
21 years.

if one can get that kind of service out of them, maybe they are worth the extra bucks up front

i am kinda thinkin that way :)

but with my experience with the cheap chinese mod square wave units, i will also have a closet loaded with them as well for backups
and other less than life support uses.

i bought a batch of 1500 watt xantrex mod squarewave units from costco a couple years ago for  89 bucks each,, at that price they don't have to last forever.
i sent my dad one and he got the battery leads crossed and blew it up,, took it apart and fixed it himself
apparently it had a bank of fuses soldered to the board, the just soldered in new ones and it has been working flawlessly since.
and he knows little about electronics, but does understand fuses and the use of a soldering iron.
so i guess the 1500 watt unit ain't bad for the money?

bob g

bob g
otherpower.com, microcogen.info, practicalmachinist.com
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