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Member's Forum Suggestions for a circuit/off the shelf component/device that can amplify an ac signal from 12V @ 5ma to 300V @ .25 A
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Suggestions for a circuit/off the shelf component/device that can amplify an ac signal from 12V @ 5ma to 300V @ .25 A

dafapa
dafapa over 2 years ago

I'm mostly an embedded software person (lately more pure software).  I'm getting the details of the requirements from a person that works as a protection engineer.  After getting some feedback I'm going to try to provide some more information and re-phrase the question.  

The ultimate goal is to convert a signal from a signal generator so that the voltage levels are high enough to work with the SEL 351S relay (without having to remove parts and wire things directly to the low voltage side internally).  As some people suspected its intended to be part of a test bench for simulating fault conditions.  The signal generator will be outputting something like the image below, with a maximum output range of +/-12V.  As you can see the signal contains a DC offset during the fault condition.

image

Being a utility application the base frequency is 60Hz, but harmonics up to 1200Hz have to be considered.  The goal is to scale the signal from +/- 12V to +/- 424V (I realize before I said 300V, but am now told its 300 * sqrt(2)).  The scaled signal will be connected to an input impedance of 1 Mega Ohm on an SEL 351S relay.  Someone pointed out the large disparity in input and output power (I was just being thrown numbers when I made the post).  After examining things it shouldn't need anywhere near a quarter amp - it should be at most about .5ma max.  Its not really driving a load; this is an input to a voltage sensor on the relay.  

I hope this clarifies things.

I'm updating this to include that 10 channels are also required.

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Top Replies

  • baldengineer
    baldengineer over 2 years ago +3
    This feels like an XYproblem in the making. What end task are you trying to accomplish.
  • rsc
    rsc over 2 years ago +2
    What frequency AC input do you need to amplify?
  • shabaz
    shabaz over 2 years ago in reply to dafapa +2
    What's the actual goal you're trying to achieve (i.e. if you could start at the beginning, before getting to your immediate objective). Just trying to guess, it sounds like some sort of industrial power…
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  • michaelkellett
    0 michaelkellett over 2 years ago

    I'm responding to your improved spec.

    The problem you have is that the fault offset won't propagate through a transformer very well.

    The obvious way is to use an amplifier capable of generating the signal you want.

    You could buy one from these people:

    https://avtechpulse.com/high-voltage/av-110a/

    There are quite a few people making this kind of thing - you may find a cheaper source.

    Or you could make one, or get someone like me (that's NOT an offer Relaxed) to make one.

    If you buy it in (of the shelf or custom made) expect to pay some serious money !

    MK

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  • michaelkellett
    0 michaelkellett over 2 years ago

    I'm responding to your improved spec.

    The problem you have is that the fault offset won't propagate through a transformer very well.

    The obvious way is to use an amplifier capable of generating the signal you want.

    You could buy one from these people:

    https://avtechpulse.com/high-voltage/av-110a/

    There are quite a few people making this kind of thing - you may find a cheaper source.

    Or you could make one, or get someone like me (that's NOT an offer Relaxed) to make one.

    If you buy it in (of the shelf or custom made) expect to pay some serious money !

    MK

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  • dang74
    0 dang74 over 2 years ago in reply to michaelkellett

    I was thinking the same way as you because I noticed the DC component in the waveform that tries to achieve the fault condition.  I wonder though if that's the kind of natural behavior you would get you first turn on an AC signal with a DC bias.  Perhaps the gradual decay in DC that is shown in the waveform would indeed occur.  I know it's not a good idea to apply DC to a transformer, so the applied signal should only occur for a short duration.  So maybe all that is required is a transformer.

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  • michaelkellett
    0 michaelkellett over 2 years ago in reply to dang74

    If it were me for a one off, I would have a go at cobbling together a rig with a transformer and DC added to the output (possibly by charged up capacitor switched in by a relay, with suitable resistor to get the decay curve right.).

    But then I looked at the "relay" its going to be testing and thought that if you are in that league of gear then you would expect to use a decent test rig !

    MK

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  • dang74
    0 dang74 over 2 years ago in reply to michaelkellett

    That would definitely give you some control on shaping the decay.

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