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Isolation Transformer

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  • Sajid khan
    replied
    Thanks all for the nice words


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  • Besoeker3
    replied
    Now now...

    I was in the power electronics for over 50 years. Design and manufacture. I still do consultancy in that field.
    At the tender stage, we had to guarantee efficiency and compliance on harmonics compliance. Failure to meet and demonstrate that we had met that compliance could mean either swingeing financial penalties or flat out rejection of the kit - and no payment at all. Neither of those happened.

    I did all the fundamental design calculations. Including the mitigating measures for harmonic compliance. What can I say?

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  • Hv&Lv
    replied
    Originally posted by Besoeker3 View Post
    From the paper:

    "It decreases current waveform distortion and improves power factor."

    That's just wrong.
    As I, and others here have noted, it will not mitigate harmonics.
    http://www.apqpower.com/assets/files...mMitigTech.pdf

    I’ve never used this for this application. I have read several papers on it and have seen some put in installations that use them for this purpose.

    i will assume every paper I have ever read on this subject is wrong then...

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  • Besoeker3
    replied
    From the paper:

    "It decreases current waveform distortion and improves power factor."

    That's just wrong.
    As I, and others here have noted, it will not mitigate harmonics.

    Leave a comment:


  • topgone
    replied
    Originally posted by gar View Post
    191010-2100 EDT

    Besoeker3:

    The word transformer without any modifier usually means a transformer with multiple separate windings that are not conductively connected internally in the transformer, and/or share the same current paths.

    When a modifier is added to transformer, then it implies something is different. So we have as examples auto-transformers, constant voltage transformers, RF transformers, and the isolation transformer.

    If the primary voltage has harmonic content, then the electrostatic shield of an isolation transformer will have no effect on that harmonic content. Filtering is required.

    .

    Agree. Define your problems and then look for solutions. Perhaps, the guy may have been given a clue on how somebody did solve his own problem! But unique problems need unique solutions, IMO.

    Leave a comment:


  • gar
    replied
    191010-2100 EDT

    Besoeker3:

    The word transformer without any modifier usually means a transformer with multiple separate windings that are not conductively connected internally in the transformer, and/or share the same current paths.

    When a modifier is added to transformer, then it implies something is different. So we have as examples auto-transformers, constant voltage transformers, RF transformers, and the isolation transformer.

    If the primary voltage has harmonic content, then the electrostatic shield of an isolation transformer will have no effect on that harmonic content. Filtering is required.

    .


    Leave a comment:


  • Russs57
    replied
    Sounds like you need a true on-line UPS. Given that you have generators that implies you will have an ATS. Typically it is more economical to run 3 phase 480 and have a transformer near/in the UPS to get the 3 phase 208 (or whatever you use in your area).

    I have been involved with hospitals for 40+ years now and it is a sad fact that Data/I.T. gets a more robust electrical system.

    Leave a comment:


  • Hv&Lv
    replied
    Originally posted by Besoeker3 View Post

    An isolation transformer is not a fix for those issues.
    http://www.isca.in/IJES/Archive/v6/i...S-2017-053.pdf

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  • Besoeker3
    replied
    Originally posted by Sajid khan View Post

    Yes By isolation transformer i mean the transformer with electrostatic shielding that will be used to suppress harmonics.



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    It won't suppress harmonics.
    You need a filter for that.

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  • Sajid khan
    replied
    Originally posted by gar View Post
    191010-1101 EDT

    What is an isolation transformer? That needs to be defined.

    I would not classify an ordinary transformer as an isolation transformer. It does provide DC isolation, and it does more or less remove common mode noise, but does not remove normal mode noise. See
    https://micro.rohm.com/en/techweb/kn.../01-s-emc/6899
    Nor does an ordinary transformer prevent capacitive coupling from primary to secondary.

    Generally I would expect the definition of an isolation transformer as having an electrostatic shield added to an ordinary transformer.

    Will an isolation transformer solve all the different problems Sajid has? No.

    So the real question is what are the real problems?

    Short time voltage drop out, a few cycles, could be very important. This will require a motor generator with lots of inertia, or an electronic UPS.

    High voltage spikes can probably be reduced with voltage clampers (MOVs and other devices).

    High frequency noise will require filters.

    Internal problems like differential ground path noise require some sort of isolation, or using differential signaling circuits.

    .
    Yes By isolation transformer i mean the transformer with electrostatic shielding that will be used to suppress harmonics.



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  • Besoeker3
    replied
    Originally posted by gar View Post
    191010-1101 EDT

    What is an isolation transformer? That needs to be defined.
    Um......one where the primary and secondary are not electrically connected?

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  • gar
    replied
    191010-1101 EDT

    What is an isolation transformer? That needs to be defined.

    I would not classify an ordinary transformer as an isolation transformer. It does provide DC isolation, and it does more or less remove common mode noise, but does not remove normal mode noise. See
    https://micro.rohm.com/en/techweb/kn.../01-s-emc/6899
    Nor does an ordinary transformer prevent capacitive coupling from primary to secondary.

    Generally I would expect the definition of an isolation transformer as having an electrostatic shield added to an ordinary transformer.

    Will an isolation transformer solve all the different problems Sajid has? No.

    So the real question is what are the real problems?

    Short time voltage drop out, a few cycles, could be very important. This will require a motor generator with lots of inertia, or an electronic UPS.

    High voltage spikes can probably be reduced with voltage clampers (MOVs and other devices).

    High frequency noise will require filters.

    Internal problems like differential ground path noise require some sort of isolation, or using differential signaling circuits.

    .

    Leave a comment:


  • Besoeker3
    replied
    Originally posted by Hv&Lv View Post

    That kind of answers your question.
    I would definitely put the isolation transformer in.
    An isolation transformer is not a fix for those issues.

    Leave a comment:


  • dkidd
    replied
    I think that harmonic mitigating transformers would be a more appropriate choice.

    https://www.hammondpowersolutions.co...ng-transformer

    Leave a comment:


  • Hv&Lv
    replied
    Originally posted by Sajid khan View Post

    Power source is not much stable as we have backup generators
    Yes we have a problem of surges and spikes during lightning and switching on and off of mechanical equipments
    Other equipment comprise of ORs and ICus equipment which are sensitive to harmonics and isolation transformers usually required for such applications
    Yes UPS harmonics in the mains is a problem..


    Sent from my iPhone using Tapatalk
    That kind of answers your question.
    I would definitely put the isolation transformer in.

    Leave a comment:

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