Inverter modification caused fault

rhuzel24
rhuzel24 Registered Users Posts: 1
in Advanced Solar Electric Technical Forum #1
can i ask some advice why our converter 1500w turn into fault when we installed a 4 capacitor (450volts and 100uF)? thank you.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #2
    Re: New Inverter

    I guess my question, is why would you do that?

    A set of capacitors across an AC inverter will take a fair amount of current with a 90 degree lead... I would bet that most inverters do not like purely capacitive loads anyway (they may not really do well with purely inductive loads either).

    If you where taking about motor starting capacitors, or attempting to charge a capacitor bank for some experiment/photo strobe/spot welding--Then usually you would put a ballast resistor (or something else) in-line to reduce the surge current.

    Otherwise, there is usually not much of anything useful from connecting capacitors directly to an AC power source.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: New Inverter

    (Moved to its own thread.)

    Not only why did you do this, but where and to what inverter?
    Caps on the DC side should make no difference (and improve nothing as well).
    Caps on the AC side as Bill said is trouble. An MSW inverter would be especially "unhappy" about this.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: Inverter modification caused fault

    My guess is he was trying to turn a MSW inverter into a PSW inverter, using the capacitor to smooth out the mess of spikes and square waves.
    If only it were so simple to do that. :cry:
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #5
    Re: Inverter modification caused fault

    Lucky only a fault. Probably due to overheating on output MOSFET's.

    Output MOSFET power dissipation relies on low ON state voltage across the MOSFET when the current passing through them is at high level. A large capacitance on MSW inverter output will cause high power dissipation (overheating).
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