• DURITC 1kW 230V Inverter/UPS

    From G8MNY@21:5/101 to TECH on Wed Jul 31 07:40:08 2019
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    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 & light weight it is.
    ________________________
    / \
    │ ┌───┐ │
    │ │ ▐ │ (0) [=====] [█] │
    │ │▄ ▄│ │
    │ └───┘ │
    ─┴──────────────────────────┴─

    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.

    ┌───────┐ ┌────────────┐
    L─┤High V ├─────┤340v HT RECT├───<──────────────────────────────┐
    N─┤outputs│ HT │ & FILTER ├───<───┐ ┌──┐ ┌──┐ ┌──┐ ┌──┐ │
    └──┬────┘ └─┬─────────┬┘ ~ ┌┴──┴┐┌┴──┴┐┌┴──┴┐┌┴──┴┐┌┴──┴┐
    /│\ \│/ \│/ │200W││200W││200W││200W││200W│
    │drive I│mon V│FB │ INV││INV ││INV ││INV ││INV │
    ┌─┴──┐ ┌───┴────┐ ┌┴─────┐ └┬──┬┘└┬──┬┘└┬──┬┘└┬──┬┘└┬──┬┘
    │50Hz├──<──┤CONTROL ├─>─┤HF PWM├─>┴──)──┴──)──┴──)──┴──)──┘ │
    │ Osc│ on │fan │ on│ OSC │drive│ 30A │ │ │ │
    └────┘ │overload│ └──────┘ |fuses| | | |
    │12 V? ├──<─────────────┴─────┴─────┴─────┴─────┴<
    └────────┘ 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 stepped waveform output.

    OUTPUT WAVEFORM
    +340V┤ ┌───┐ Fixed Voltage
    -230V│ │ │ Fixed pulse width
    │ │ │
    0V ┤──┘ └──┐ ┌─
    │ │ │
    -230V│ │ │
    -340V┤ └───┘

    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, & 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.

    20A ┤ 1kW Restive │ 100W load
    │ Load │\ + 0.1uF
    6A ┤ ┌───┐ │ \_ │
    0A ┤──┘ └──┐ ┌─ ─┘ │──┐ _│─
    -6A ┤ └───┘ │ │ /
    │ │/
    -20A┤ │

    MODS
    1/ Added HT fuse after 340V Cap smoothing!
    + ┬─o-o──┬──────────┐
    │ 3A FET FET L&N
    340V === ├─L LOAD N─┤ 50Hz
    │ FET FET Amps
    - ┴──────┴──────────┘

    2/ Added a mains IEC in socket small 25W mains transformer & 3 pole changeover
    relay for bypass (UPS).
    ___________________________________________
    L │ \_________
    │ _______ ┌─────┐ __ ON │ L
    MAINS )||(18V /\│ ┌──┴──┐ │ \_ L
    INPUT )||(AC Bridge │Relay│ Start / INVERTER LOAD
    )||(____│_\/ └──┬──┘ Up└──── N
    │ ┴─────────┴0V │ _________ N
    N____│______________________________________/
    With no smoothing on the relay the relay releases quick on mains fail,
    changes mains over & the inverter then starts up.

    3/ Added standby trickle charging, up to 1A Max @ 13.5V regulated.
    ┌────┐
    18V┤>├┬──────┬─┤7815├──┤>├─> +Batt
    AC┤>├─┘ 470u===└──┬─┘
    0V ─┴────┴────────> -Batt

    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 ||(_ /\
    200W _│ / \ ┌──┬─────┬───── +340V
    PWM ||(_ /Fast\ o│ │ │u1
    INVERTERS _│ /Bridge\____(((((() === === TO
    ||(_ ┌Rectifier ======= │400V │ L & N
    _│ │\ / (((((() │CAP │ 50Hz AMPS
    ||(_ │ \ / │o │ │ │
    _│ │ \ / │ └──┴─────┴───── 0V
    ||(___│___\/ │Choke Starts
    └────────────┘are in phase!

    8/ Made balanced L output mains filter (from old HF choke & 2x 6n8 caps to
    ground).
    L───┐o ┌───────┬───── L
    (((((() === Inverter
    Inverter ======= Xtype ├─E O/P To
    Output (((((() Caps === Relay
    N───┘o └───────┴───── N
    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...

    L─┤├─100Ω──┬──┤>├──┬─220Ω─┬── 100Ω will catch fire with 340V pulses into
    C ┌─)─┤>├───┤+ _│_ it despite the 1uF looking like 3k3 @ 50Hz!
    1uF │ │ === /_\`12V I solved this with a 330Ω 5W in its place!
    │ └─┤<├───┤100u │
    N────────┴────┤<├──┴──────┴──


    Why don't U send an interesting bul?

    73 De John, G8MNY @ GB7CIP


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    * Origin: HAMRADIO telnet lu9dce.dynu.com (21:5/101)