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G8MNY  > TECH     24.12.10 08:38l 105 Lines 4325 Bytes #999 (0) @ WW
BID : 3188_GB7CIP
Read: GUEST
Subj: DURITC 1kW 230V Inverter/UPS
Path: IZ3LSV<IK2XDE<DB0RES<ON0AR<UA6ADV<GB7CIP
Sent: 101224/0222Z @:GB7CIP.#32.GBR.EU #:3188 [Caterham] $:3188_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To  : TECH@WW

By G8MNY                                        (Updated Mar 08)
(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 & 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.

  ÚÄÄÄÄÄÄÄ¿     ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿
LÄ´High V ÃÄÄÄÄÄ´340v HT RECTÃÄÄÄ<ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
NÄ´outputs³  HT ³  & FILTER  ÃÄÄÄ<ÄÄÄ¿  ÚÄÄ¿  ÚÄÄ¿  ÚÄÄ¿  ÚÄÄ¿  ³
  ÀÄÄÂÄÄÄÄÙ     ÀÄÂÄÄÄÄÄÄÄÄÄÂÙ ~    ÚÁÄÄÁ¿ÚÁÄÄÁ¿ÚÁÄÄÁ¿ÚÁÄÄÁ¿ÚÁÄÄÁ¿
    /³\          \³/       \³/      ³200W³³200W³³200W³³200W³³200W³
     ³drive      I³mon     V³FB     ³ INV³³INV ³³INV ³³INV ³³INV ³
   ÚÄÁÄÄ¿     ÚÄÄÄÁÄÄÄÄ¿   ÚÁÄÄÄÄÄ¿ ÀÂÄÄÂÙÀÂÄÄÂÙÀÂÄÄÂÙÀÂÄÄÂÙÀÂÄÄÂÙ
   ³50HzÃÄÄ<ÄÄ´CONTROL ÃÄ>Ä´HF PWMÃÄ>ÁÄÄ)ÄÄÁÄÄ)ÄÄÁÄÄ)ÄÄÁÄÄ)ÄÄÙ  ³
   ³ Osc³ on  ³fan     ³ on³ OSC  ³drive³ 30A ³     ³     ³     ³
   ÀÄÄÄÄÙ     ³overload³   ÀÄÄÄÄÄÄÙ     |fuses|     |     |     |
              ³12 V?   ÃÄÄ<ÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÁ<
              ÀÄÄÄÄÄÄÄÄÙ                                  12V @ 125A

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 output.

OUTPUT WAVEFORM
  +340V´  ÚÄÄÄ¿ Fixed Voltage
  -230V³  ³   ³ Fixed pulse width
       ³  ³   ³
   0V  ´ÄÄÙ   ÀÄÄ¿   ÚÄ
       ³         ³   ³
  -230V³         ³   ³
  -340V´         ÀÄÄÄÙ

The control for this lot is not simple there is monitoring of temperature,
output current, supply Volts, etc. So working without a diagrams is not easy,
still I have it going now & done some worth while modifications....

PULSE CURRENT
If a capacitive load from say a 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.

   20A ´  1kW Restive      ³ 100W load      
       ³     Load          ³\ + 0.1uF
    6A ´  ÚÄÄÄ¿            ³ \_       ³ 
    0A ´ÄÄÙ   ÀÄÄ¿   ÚÄ   ÄÙ   ³ÄÄ¿  _³Ä
   -6A ´         ÀÄÄÄÙ         ³  ³ / 
       ³                          ³/  
   -20A´                          ³

MODS
1/ Added HT fuse after 340V smoothing!
2/ Added a mains IEC in socket & 3 pole changeover relay for bypass (UPS).
3/ Added standby trickle charging, up to 1A @ 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 HF choke after bridge rectifier, reduced QRM.
8/ Made balanced L output filter (from old HF choke & 2x 6n8 caps to ground).

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...

LÄ´ÃÄ100êÄÄÂÄÄ´>ÃÄÄÂÄ220êÄÂÄÄ     100ê will catch fire with 340V pulses into
   C     ÚÄ)Ä´>ÃÄÄÄ´+    _³_      it despite the 1uF looking like 3k3 @ 50Hz!  
  1uF    ³ ³      ===    /_\`12V  I solved this with a 330ê 5W in its place! 
         ³ ÀÄ´<ÃÄÄÄ´100u  ³
NÄÄÄÄÄÄÄÄÁÄÄÄÄ´<ÃÄÄÁÄÄÄÄÄÄÁÄÄ 

FUTURE
Some day I want to make it pseudo sine wave output. This I think can be done
quite efficiently by changing the large HT Cs for low value pi filter just to
remove the HF & use a CR shaped ramp up & down @ 100Hz AC applied to the HF
inverter loop regulation.

+340V´  .Ä.   5% idle
+230V³ /   \ Ý      Ý
     ³|     |
   0V´Ù+45% À¿ -45%Ú
     ³       |     |
-230V³        \   /
-340V´         `Ä'

So instead of switching a full the 340V for 30% ñ outputs (230V RMS) the switch
will switch say @ 45% ñ a ramp up & down, avoiding much of the huge peak edge
currents & associated 50Hz HF QRM.


Why don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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