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  1. #21
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    On the page
    http://services.eng.uts.edu.au/~venk...2/ch04s2p1.htm
    It says
    The main purpose of the fully-controlled bridge rectifier circuit is to provide a variable dc voltage from an ac source.
    You won't find output waveform like this,

    As it is for AC control.
    The out for DC motor control is,

    And is very similar to

    except the difference of firing angle spikes as i earlier said.
    A dimmer circuit gives an output like you are confusing with.

    Have a look at this page.
    http://sound.westhost.com/lamps/dimmers.html
    Once you know something, the documentation then becomes very clear...


    1 members found this post helpful.

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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    Sir ,, this is the first time I heard about the dimmer circuit !! I must first read it !!

    so do you think we can get an output like what we want !! from the dimmer ckt ?!

    what kind of configuration added to circuit to have the output ?!

    - - - Updated - - -

    you know what !! I think you are definitely right .!!! I'm just confused :) thank you sir



  3. #23
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    Dear ALERTLINKS
    If you can help us , I really want your help in this subject .. and by the way .. I'd really thank you for everything did it for me !

    but I need something ..

    my output in the LAB on the Oscilloscope give us wrong waveform . .. . I don't know what's the problem .. BUT , in the Protoues ISIS everything works as we need ..

    what will be the problem !!

    here the photo that describe my problem !! I need your help ! I can't find the problem , since nothing goes wrong in the ISIS Protoues
    error in my output.jpg

    this photo will help for more details !



  4. #24
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    These two capacitors are wrongly connected. See if this is the case.



    The other two MOC3021 are wired correctly.
    Compare with standard circuit.



    In post #20,
    Also , I don't get it form your design ,, when you put the same component in the upper 2 thyristors but in other hand of the lower 2 thyristor in completely different connection form the opto-coupler into thyristor !!

    you can see from your design U2 & U4 are the same .. and U1 & U3 are the same but not the same for all of the thyristor ?!

    why we just but the same material for the full bridge ..
    Were you indicating about this error, which i didn't understood and didn't noticed ?
    Once you know something, the documentation then becomes very clear...



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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    actually , I change the circuit you gave it !! I mean I made my modification .. and everything in the Proteus is working good .. the problem in hardware in lab !

    the output like I post it last time , I don't know how to solve this issue ~!



  6. #26
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    Disconnect motor and C9. Put a resistive load such as a 100W bulb. Observe the waveform, using a oscilloscope at output and drive to gates of all four SCRs. See the difference between drive and output of individual SCRs.
    Once you know something, the documentation then becomes very clear...



  7. #27
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    I'm already using R-load .. but still have the problem !!



    •   Alt2nd December 2012, 19:00

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  8. #28
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    Take snaps of inputs to gates with respect to input sine wave and output and post waveforms.
    Once you know something, the documentation then becomes very clear...



  9. #29
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    hi....ur work is impressive....i have been working on this for few months but have certain issues...i would be happy if u cud mail me ur proteus model.....awaiting ur reply...

    cheers!



  10. #30
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    @ALTERLINKS.

    Your work is really impressive. You have great knowledge. edaboard.com has great experts. You are also one of them.



    •   Alt10th April 2013, 21:28

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  11. #31
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    can u send e the source code file pls...

    - - - Updated - - -

    in the design that u ve used, where is the POT-HG to vary the firing angle???????or have u implemented anyother means to vary the firing angle....pls reply early...



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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    I don't know how ALTERLINKS do this. But he does very well. He knows how to make thing easier.



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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    Quote Originally Posted by Barbarawi View Post
    Hi All ,,

    I'm using ISIS Proteus in my Graduation Project ..

    I could not find the Issue in my circuit when I use INDUCTOR with Resistance !!

    my project about "How to control the DC motor by changing firing angle of the SCR thyristor"

    so when I pressed to START .. the first cycle start from "90 degree" as I controlled it in my code in C "

    here are the result in the picture ~

    Attachment 82340

    you can see from the picture the first cycle is only happened due to Inductor !! WHY ?!

    the Load parameter ::
    R=10 Ohm
    L=31.8 mH

    what would be the problem ?!

    for more info.
    the circuit contained four 4- Opto-coupler to give the pulse that comes from the PIC16f877A to Optocoupler to SCR thyristor
    each SCR have his own opto-

    I need your expert
    I'm in need of studying the behaviour of those circuits ;can you plz give me the schematic of this 4 scr controlled by a microcontroller?
    Thanks



  14. #34
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    Further development and continuation of thread is here.
    Problem with stability of DC motor
    An relevant page with info:
    http://www.joliettech.com/model_1681...ion_manual.htm
    As you can notice, Barbarawi has not logged into edaboard since then, (his last activity is on 1/1/2013) he may not be noticing your requests.
    Once you know something, the documentation then becomes very clear...



  15. #35
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    hi.....i read the problem with stability of DC motor link and found how to vary the firing angle....my doubt is why are the triggering pulses comin out from the optocoupler connected differently for upper arm and lower arm thyristors....reply



  16. #36
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    They are controlled separately according to each half cycle of AC wave.
    Once you know something, the documentation then becomes very clear...



    •   Alt21st April 2013, 13:58

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  17. #37
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    in my project i ve used 8051 to trigger the thyristors....but am nt able to synchronise the pulses with the output of ZCD....wat to do?can u help me if i send u the file?

    - - - Updated - - -

    i have used a POT to vary firing angle and then apply to ADC where by coding i produce reqd delay after i ve got the pulse from ZCD.but the problem s tat when i vary the firing angle, the pulses doesn't shift accordingly.



  18. #38
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    but the problem s tat when i vary the firing angle, the pulses doesn't shift accordingly.
    So it is a software problem. You have to correct its working before you can use it. Your approach is ok but problem is where you set delay after detecting zero crossing according to ADC sample setting of pot value.
    You have 10mS duration of one half cycle (50Hz). If ADC sample is of 8bit, you have 0-255. If you make a delay routine which takes 35uS to execute, it will take about 9mS if it is called 255 times. you have 255 steps of speed regulation calling this delay routine number of times according to ADC value. After that you set for the trigger pulse.
    Explain how you are implementing it. You can post your code in microcontroller section if problem is not solved, http://www.edaboard.com/forum31.html
    Once you know something, the documentation then becomes very clear...



  19. #39
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    i finished the simulation part....it works properly with R load but not with RL load....

    can u pls help me with the AC thyristor model explanation for modelling SCR in pspice ..



  20. #40
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    Re: Need help :: FULLY-CONTROLLED SINGLE-PHASE SCR BRIDGE RECTIFIER: RL LOAD

    Gate reference here is floating... controlled Rectifier.png.....I want to control the scr from microcontroller which has separate grounding. I dont want to mix the Microcontroller Ground with High voltage ground. How to do it..
    I think the gate current need to flow in microAmps with respect to Cathode of scr. But Cathode of SCR is in +Ve output of DC voltage.. Help me in this regard



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