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GEKO diesel generator has 60 kVA electric power. Our switch mode power supply connected to this generator via passive filter DL-50EA3 and 6-pulse bridge rectifier (see the schematic). In this configuration we suffering from the filter excitation:

enter image description here (yellow - input voltage divided by 10 = 200V/div, blue - current 5Amps/Volt = 25A/div)

If the power supply connected to the regular electric network - everything is OK.

Schematic:

enter image description here

The equipment connected to the generator suffers from this parasitic oscillation and we need to suppress it as we can.

One possible solution is to put additional filter between generator and rest equipment in the following configuration:

enter image description here

Can anyone suggest the filter? Or maybe we miss some extra solution.

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Sounds like you may be violating the Middlebrook criterion: If the output impedance of the generator combined with the input filter is less than the input impedance of the power supply AT ANY FREQUENCY the combination can become unstable. It works when connected directly to the mains because the impedance of the normal AC supply is likely lower than the generator. You could do some analysis to see if there's any way to reduce the impedance connected to the power supply by modifying the filter.

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  • \$\begingroup\$ Thank you very much for the contribution. Is there any possible solution? \$\endgroup\$
    – Roman Matveev
    Commented Jun 24, 2014 at 8:34
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    \$\begingroup\$ The only solution is to replace or modify the filter so that the generator/filter combination presents a lower impedance to the input of the SMPS. To see if this is really the issue can you connect the generator directly to the SMPS input bridge without the filter? \$\endgroup\$
    – John D
    Commented Jun 24, 2014 at 14:31

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