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Ripple on low voltage

Peterd
I look after a small fairground type railway. It is powered via a transformer and full wave rectifier and runs at around 35 volts. At recent inspections it has been noted that it fails as there is around 24 volt ripple on the 35 volt dc, which is not surprising as there is no smoothing. Apparently according to the person undertaking the inspection, who states it is to bs7671, the ripple should be no more than 10% ripple, however I cannot find any such requirement.

Has anyone got any experience of this type of thing, I am loathe to add a capacitor to smooth the dc - it would have to be probably around 0.1F, and ripple current in it could well be a problem.

Any thoughts on this would be appreciated, is there an actual requirement on ripple, or is it OK to just have full wave rectified dc as long as the peak voltage does not exceed the elv limits of 120v dc or 50 v ac rms .
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    And if anyone can tell me how to remove the extra copies of the attached files that would be great - they do not appear in edit either in the text editor or in the source view, but there they are.

    Just take the top zip for the LTspice model (the asc file)  and the plotting options.


    Edit fixed thta part , thanks Elizabeth.


    PS in the world of spice you need to define sine waves by their single sided peak, so 230V RMS is about 330pk, transformers you specify by the unloaded inductance and a magnetic linking factor 'k' nearly one but not quite in a real system.

    Such sims are very good as demonstrating the peak voltages and currents on switches and so on during switching, if you put in all the components that are not on the simple schematic, like the capacitance of cable cores to each other and the small series resistances that all real parts have.

    M.
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  • 0
    And if anyone can tell me how to remove the extra copies of the attached files that would be great - they do not appear in edit either in the text editor or in the source view, but there they are.

    Just take the top zip for the LTspice model (the asc file)  and the plotting options.


    Edit fixed thta part , thanks Elizabeth.


    PS in the world of spice you need to define sine waves by their single sided peak, so 230V RMS is about 330pk, transformers you specify by the unloaded inductance and a magnetic linking factor 'k' nearly one but not quite in a real system.

    Such sims are very good as demonstrating the peak voltages and currents on switches and so on during switching, if you put in all the components that are not on the simple schematic, like the capacitance of cable cores to each other and the small series resistances that all real parts have.

    M.
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