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33 KHz Step Up transformer

Discussion in 'High Voltage' started by naumank, May 28, 2016.

  1. naumank

    naumank Member

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    Hi all

    I have a power amplifier which can output 200 Vpp with output source resistance of 5 ohm and an echo sounder transducer having input impedance of 80 ohm+/- 24 ohm at 33 KHz. I need some step up transformer with 1:3 so that i would be able to deliver at least 600 Vpp from power amplifier to my load at 33 KHz.

    Is there any COTs step up transformer available for this meeting desired requirement?

    Kindly help me for my problem?

    Thanks & Regards
     
  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi nau,
    If you recall I was helping you on another Forum with this project.
    I did point out that 200Vppk was only ~70Watts effective power, which would not be sufficient for 1500 mtrs, at 33kHz

    Eric
     
  3. naumank

    naumank Member

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    Hi Eric

    Thanks for help. Yes, you were right as i was not considering the noise level (@33 KHz) appearing at transducer for a given sea conditions which came to be quite higher as compared to echo level i calculated. As output voltage of power amplifier is limited to 200 Vpp, I think a step up transformer b/w power amp and transducer of 1:3 ratio or 1:4 ratio will do the work. What you say about this?

    Note: One immediate problem i see with this approach which i also have to solve is of T/R switch as most T/R switches i found limited to +/- 130V only?
     
  4. dave

    Dave New Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    The transformer may step up the voltage but it won't give you any more power. If the amp is limited to 70W then that's all you get (actually slightly less, because of transformer losses).
     
  6. naumank

    naumank Member

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    Hi alec
    Thanks for reply. Sorry, i did not mention that power amp can deliver 10 A continuous current.
     
  7. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I looked for one hour. I could not find a "off the shelf" standard transformer.
    The closest one I found is 1/6 the size you need.
    The problem with a custom part is that it takes engineering time to design and make one part. So the price is very high.
    Please send more information on the transducer and power amplifier.
     
  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Last edited: May 28, 2016
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  9. naumank

    naumank Member

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    Thanks for reply. I attach the data sheets
     

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  10. naumank

    naumank Member

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    Thanks. Do you mean u use "resistor/diode network" in place of T/R switch? Will this withstand 800 Vpp as in my case?
     
  11. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    The transducer can operate at two frequencies. (33k and 200khz) I can find transformers for 200khz but your amplifier can not do that.

    What about running two amplifiers 180 out of phase? So one pulls up while the other pulls down. That will double you output voltage and 4x the power.
     
  12. naumank

    naumank Member

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    Can you kindly explain how to connect two amplifiers with my transducer to double output voltage?
     
  13. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi nau,
    check that the ex-printer piezo 33kHz transducer can withstand 600Vppk.

    E
     
  14. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    1) Your amp is rated at 100 volt supplies absolute max, 75 volt typical. So I reduced the supplies down to +/-90 volts. The output can not pull to the supplies. So 80+80=160Vp-p is the max you can get.
    2) There are some details not included. I would AC couple the output of one or both of the amps.
    3) If this diagram does not speak to you then this project is above you level.
    upload_2016-5-28_12-52-7.png
    This is how I would do the 3:1 transformer.
    upload_2016-5-28_12-59-49.png
     

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  15. naumank

    naumank Member

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    Hi Eric
    As impedance given is 80 ohm and max input power @ 1% Duty cycle is 1000 watt, i think it should withstand approx. 800 Vpp with duty cycle < 1%.
     
  16. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    I think for any motion-inducer transducer with a dynamic load, one needs to consider a good damping factor very load load regulation of source voltage due to back pressure. In audio it is most important for bass as this has the highest displacement. Since motion induced presure that generates load will create noise or distortion.

    I would not consider anything more than 10% unless there is a some switching problem with high L/R ratio.

    600V^2/80 Ohm= 4500 VAR, how much % is real power depends on it's piezo capacitance ESR

    If you have a 3:1 step up then load transfer to source becomes 80/(3^2)= 8.9 so you gen. needs a source impedance < 10% or < 0.9 Ohms not 5 Ohms which drops significantly the Vout when the load is applied.

    With 200V and 10A avail, you only have 2000 VAR not the 4500 VAR you specified.
    I'm not sure if you are using avg, rms or peak or p-p but at least, I hope you are consistent.
     
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  17. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Just picking numbers out of the air. (water)
    600Vp-p = 300V pk = 3.75A pk = 1125 watts pk = 800watts
    ----------edited-----------
    I agree with Tony you will have about 10A pk in the amplifier.
     
  18. naumank

    naumank Member

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    Hi Tony Stewart

    Thanks very much for help.

    I am little confused as maximum power transfer theorem says that maximum power will be transferred when source impedance will be equal to load impedance. But it is also very logical (according to voltage divider rule) that source impedance should be as less as possible (Ideally 0 or practically < 10% of load) so that maximum voltage can be transferred to load. Can you kindly explain? Is it a difference of maximum power transfer and maximum voltage transfer?


    As ronsimpson also indicated, 10 A is peak current that implies i have effectively 100 Vp x 10 Apk =1000 VAR_pk from power amplifier and in case of 3:1 step up, VAR_pk required is 300Vpk^2/80 Ohm = 1125 VAR_pk. Am i correct?

    Will using two power amplifier operated in parallel (doubling Ipk current) will solve the problem as net VAR_pk of power amplifiers will be doubled but source impedance problem (i.e. <10% of load) will still be there?

    Can you kindly suggest some alternate solution?
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi nau,
    As you are planning to use the Piezo transducer from a printer head as a water depth measurement transducer, my strongest advice would be to determine how you intend to mount the transducer and carry out shallow water tests using the Amp to directly drive the transducer, you may have to tune the cable/transducer to get resonance at 33kHz.

    This should give you some empirical data regarding the transducers performance.

    Do you have any data on the beam width/pattern you are likely to get thru water.? for a 33kHz its typically around 15deg, 22degs.

    The dual 210/30kHz transducers [ 1kW] I used in my echo sounder products, cost around £1500GBP.

    Could you say what is your intended sea area of operation that requires a maximum depth of 1500 mtrs and the purpose for taking soundings down to this depth.?

    When you said on the other Forum you also want an 'echo gram' display of the sea bed, do you mean a paper Chart or a LCD monitor display.?

    Eric
     
  20. naumank

    naumank Member

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    Hi Eric

    I think there is some confusion about the transducer i have selected (so far) for my design. I have attached its data sheet. Its beam width is approx. 22 deg at 33 KHz. Can you kindly explain why you call it "printer head as a water depth measurement transducer"?

    Experimentation is a very good idea but unfortunately i have no hardware available with me currently so first i have to mature my design and then go for hardware purchase.

    TC2122 transducer will nearly cost me 2,700 euro so i have to be sure that it will do work for me.

    This echo sounder needs to be installed (preferable mount through hull of ship) on hydro graphic survey ship to aid in sea bottom survey.

    This echo gram will be continuously updating on LCD monitor display and also needs to be recorded for later analysis.
     

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  21. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi nau,
    Sorry about that, I must have got my wires crossed regarding your transducer.:(
    Looking thru the TC2122 datasheet, that should get the job done, its similar to the specifications I have used.

    If you are designing the electronics/software the receiver should include some method of adjustable transmission 'noise' suppression and time swept gain control.
    It is also helpful to have an adjustable 'Depth acceptance Gate' to improve a sea bed lock.

    E

    https://www.simrad.com/www/01/nokbg0240.nsf/AllWeb/E518F09ADFFDC337C125718D0042856F?OpenDocument
     
    Last edited: Jun 2, 2016

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