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Power inverter output too high

Discussion in 'Troubleshooting and Repair' started by wingnutter, Jul 16, 2013.

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  1. wingnutter


    Jul 16, 2013
    Hi Wise owls,

    I have a 12V 1000W 230 VAC power inverter that has on output of 300VAC and I would like to drop the voltage back to how it should be. I do not think the inverter has developed a fault, more like it was badly manufactured.

    I have tried adjusting it via a small reostat on its PCB without any joy.

    Can I place a resitor in line with the out put to get the correct voltage? If so what would be the value of the resistor and type required?

    Thanks in advance for any replies

  2. duke37


    Jan 9, 2011
    A 230V AC supply will have a peak voltage of 325V.

    It depends on the shape of the waveform as to what is measured. Most meters measure the mean voltage and then bodge the result to match the RMS value assuming a sine wave.

    The twiddle pot may be to adjust the frequency rather than the voltage, if so, you will need to reset it correctly.
  3. elebish


    Aug 16, 2013
    Switching type PS's are a pain to work on because of the frequencies used to keep the transformer (terroid) sizes down and therefore the cost. They also use a pwm (pulse width modulation) circuit to regulate the output voltage. You will need a scope to look at these pulses to effectively T/S the circuit. Do NOT use resistors to drop the output and always have a small load on the output of switching type PS's when TSing. You may want to reconsider the time you may have to spend fixing versus replacing. Ed.
    Last edited: Aug 19, 2013
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