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muhammad-ahsan-khan
Joined: 26 Mar 2008
Posts: 10
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 04 Apr 2008 5:14 square wave inductor |
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how to get square wave across an inductor in an RL circuit?
As we know , if we apply a square wave to an RL circuit, the voltage across inductor is nothing but a series of pulses due to the resistance associated with the inductor and source.
My objective is to get a pure square wave across an inductor.
how can I do it?
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laktronics
Joined: 06 Jan 2007
Posts: 945
Helped: 156
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04 Apr 2008 6:05 rl circuit square wave |
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Hi,
Keep the pulse width smaller than the time constant L/R of the circuit.
Regards,
Laktronics
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FvM
Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany
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04 Apr 2008 6:14 square wave rl circuit |
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| Depending on the application, it could be an option to restore the original waveform, either by analog or digital circuit.
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muhammad-ahsan-khan
Joined: 26 Mar 2008
Posts: 10
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04 Apr 2008 8:28 inductors square wave |
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I have tried a lot of things but it does not work.
Increasing L/R is not feasible as it will require a very high frequency in my project as L and R values are constant.In an RL circuit one gets pulses which die out exponentially hence the voltage levels will not be smooth either.
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04 Apr 2008 8:28 Ads |
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banjo
Joined: 24 Dec 2005
Posts: 644
Helped: 118
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04 Apr 2008 13:27 current inductor square wave |
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One large issue is the saturation of the inductor core. Laktronics has already stated the most common solution. Keep the time constant large so that you are limited to just the initial portions of the exponential current ramp curve. At this area, the curve is fairly linear.
You stated that you cannot change the time constant. Therefore, you would have to introduce a logrithmetic driving voltage to counteract the expoential function. Such driving voltage are difficult as they increase without bounds.
Please stop and think what you are asking. For a true sqaure wave voltage across an inductor, the current must be continually ramping during the entire flat portion. It has to do this without getting anywhere near core saturation or the impedance of the coil drops greatly.
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FvM
Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany
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04 Apr 2008 13:40 generate square wave for inductor |
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Taking the question together with your other posts, I realized that you just have been posting to parts of a problem (from a book, a class, an interview or whatever). The question could actually have been clearer!
Connect a triangular current source to your RL series circuit. You have a triangular voltage wave at the resistor and a a square wave at the inductor then. Total voltage is the superimposition of triangular and square waveform.
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