Message 20694 in TECH.WW
From: G8MNY
Date: Sun, 12 Apr 26 08:13:00 Z
Newsgroups: TECH.WW
Subject: DURITC 1kW 230V Inverter/UPS
Message-ID: <57060_GB7CIP>
Path: N2NOV|VE2PKT|PY2BIL|HB9ON|VK7AX|GB7CIP
R:260412/0820z @:N2NOV.#RICH.NY.USA.NOAM $:57060_GB7CIP
R:260412/0819Z 5047@VE2PKT.#TRV.QC.CAN.NOAM LinBPQ6.0.25
R:260412/0819Z 41641@PY2BIL.SP.BRA.SOAM LinBPQ6.0.25
R:260412/0818Z 10948@HB9ON.TI.CHE.EU LinBPQ6.0.24
R:260412/0818Z 10533@VK7AX.#ULV.TAS.AUS.AUNZ LinBPQ6.0.24
R:260412/0813Z @:GB7CIP.#32.GBR.EURO #:57060 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jan 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Not a UPS really but a high power, stepped square wave mains inverter from 12V.
It was blow up when I got hold of it it. I now have it working with new output
high voltage MOSFETS.
Having made this sort of thing before with heavy conventional transformer etc.,
I was amassed at this modern HF version, just how small and light weight it is.
________________________
/ \
DESCRIPTION
It has 5 pot core HF pulse width inverters with 2 TIP MOSFETS each handling
200W. The 5 floating secondaries are connected in series to feed a fast high
voltage bridge rectifier to a HF choke, into large 400V smoothing cap.
The pulse width feedback controls that voltage to 340V. This powers 2 high
voltage MOSFET amps (blown up) that switch the L & N to +340V for 2/3 for the
time giving the 340V peak & 230V RMS 50Hz stepped waveform output.
OUTPUT WAVEFORM
The control for this lot is not simple, there is monitoring of temperature,
output current, supply Volts, etc. So working without the diagram is not easy.
Still I have it going now, and done some worth while modifications....
PULSE CURRENT
If a capacitive load from say a good mains filter is put across the output,
then the high voltage Power MOFETs can easily be blown up again, as very high
pulse edge currents can flow.
MODS
1/ Added HT fuse after 340V Cap smoothing!
2/ Added a mains IEC in socket small 25W mains transformer and 3 pole
changeover relay for bypass (UPS).
___________________________________________
With no smoothing on the relay the relay releases quick on mains fail,
changes mains over and the inverter then starts up.
3/ Added standby trickle charging, up to 1A Max @ 13.5V regulated.
4/ Speeded up the mains fail start up time, but it is too slow for some things.
5/ Added 1uF polly across each HF inverter 12V supply rails.
6/ Added 0.1uF @ 600v across the main HT caps.
7/ Bifilar balanced wound bigger swinging HF choke after bridge rectifier,
reduced the QRM.
_______
5x ||(_ /\
8/ Made balanced L output mains filter (from old HF choke and 2x 6n8 caps to
ground).
(((((() === Inverter
Output (((((() Caps === Relay
Choke Starts
are anti-phase!
WARNING
Devices that use the reactance of mains caps to drop the mains voltage can be
destroyed on this waveform. e.g. a true RMS digital meter! As the pulse edge
puts 100x the voltage into the current limiting R or the circuit...
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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