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Plate transformer question

Discussion in 'Amateur Radio Amplifiers' started by KN4CTD, Apr 20, 2019.

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  1. KN4CTD

    KN4CTD Ham Member QRZ Page

    Did I just buy an oversized doorstop lol?
     
  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Check with they gents over in the AM forum section. Looks like a nice piece of iron to me but what you may want to do with it takes some figuring out.
     
  3. KN4CTD

    KN4CTD Ham Member QRZ Page

    Thanks.....where’s the AM forum? I just picked it up to maybe use as a plate transformer for a 1kw or so linear amplifier. I don’t know much about transformer design etc. so I figured I’d ask here. I don’t understand why they made transformers that big and heavy compared to other e/I core transformers nowadays....
     
  4. KN4CTD

    KN4CTD Ham Member QRZ Page

    Sorry, didn’t realize there was an AM forum on here!
     
  5. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    KN4CTD likes this.
  6. KN4CTD

    KN4CTD Ham Member QRZ Page

  7. N8FVJ

    N8FVJ Ham Member QRZ Page

    30% of weight is the cast end bells. The transformer is likely rated CCS (continuous) duty and can likely provide 1.5 times rated current for CW or SSB. Curious you never stated the voltage output.
     
  8. KN4CTD

    KN4CTD Ham Member QRZ Page

    Lol, I didn’t take those heavy end bells into account when I picked it up......which was foolish of me. The spec plate shows two output secondary taps @ 2000v and 2500v. Ive done no testing on it yet to determine what the true voltages are gonna be. I figure I’ll borrow my friends variac to do this. And yes, the specs online show it to be rated at 300 ma ccs.
     
  9. KN4CTD

    KN4CTD Ham Member QRZ Page

    Any suggestions on a procedure to determine what the ICAS current rating of this thing might be?
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The ICAS rating is right in the catalog per the link you provided. It's listed as 425 mA.

    Also it doesn't have taps at 2000V and 2500V according to the catalog. It has 2820Vrms across the entire secondary winding with taps at 2260Vrms, and the "DC output voltage" shown in the catalog is based on a choke-input power supply, where the DC is about 0.9x the RMS secondary voltage.

    Today using solid state rectifiers there's no reason to use a choke input design, and you'd have to find an appropriate choke which is likely to be about as big and heavy as the plate transformer. Almost nobody would do that.

    If you use a tube (or tubes) that operate at very high voltage and provide a lot of power at relatively low plate current, assuming the transformer is "okay" inside (insulation hasn't broken down from age), you could use a full-wave bridge on the 2820V secondary and have about 3950VDC from a filter bank. A pair of 3-500Zs or 4-400As or a single 4-1000A will handle that, and at 425mA load current would run 1678W DC input power; with 60% amplifier efficiency, that's a kilowatt output power.

    For low duty-cycle modes like SSB you could probably draw >500mA and be pushing legal limit power. CW, probably a little less; RTTY, quite a bit less. 3950VDC @ 500mA = 1975WDC input; at 60% eff ~1200W output.
     
    Last edited: Apr 21, 2019
    KN4CTD likes this.

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