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    Chopping of rectified dc voltage using IGBT ct60 am 18b

    For my project which is speed control of a wound rotor induction motor(or slip ring induction motor) i am using ct60am 18b igbt for the chopper part... the problem i am facing i was successful in getting a rectified output from the rotor side using power diodes and LC filter circuit... but wen it came to chopping using the igbt i cannot get the required output.... i was able to trigger the igbt alone for testing it. in the main circuit, the microcontroller (ATMEGA 32k) output is given to the base of igbt. since the output from the micro is only less than 5v i connected an optocoupler (moc8102) to d micro output n gave opto output to igbt...i was successful only in triggerring the igbt but the with the increase in voltage the output across the load connected to igbt never increased..... i was told gate current required by igbt is more and not provided by opto....0i have no clue what to do..... i am stuck ryt now.... PLease tell me what to do.... I have to chop the rectified dc output according to microcontroller output so as to maintain the speed of the motor irrespective of the load.... NEED help badly......

    •   Alt18th April 2012, 05:25

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    Re: Chopping of rectified dc voltage using IGBT ct60 am 18b

    Obvious you need to use driver circuits in between MOC8102 optocoupler and the IGBT transistor.
    You may change the MOC8102 optocoupler with a dedicated isolated driver, see for example
    Vishay VO3120
    http://www.vishay.com/docs/81314/vo3120.pdf
    http://www.vishay.com/docs/81227/81227.pdf
    HCPL-3120:
    http://www.tme.eu/dok/H/HCPL3120.pdf
    Avago ACPL-38JT:
    http://www.avagotech.com/pages/en/op...cpl-38jt-000e/

    There can be more solutions using integrated circuits
    TC4424:
    http://www.tme.eu/dok/T/tc4424a.pdf
    TC4421/TC4422:
    http://www.tme.eu/dok/T/tc4421a22a.pdf

    or discrete components


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    Re: Chopping of rectified dc voltage using IGBT ct60 am 18b

    Thanx alot!!! That filled the gap in the project... let me see how it goes..... i will post the details about my project and would like ur suggestions regarding it...



    •   Alt18th April 2012, 20:11

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    Re: Chopping of rectified dc voltage using IGBT ct60 am 18b

    Well... i tried with the optocoupler as u said and i was successful in triggering the igbt accordin to the output from micro.... but wen the chopper circuit was connected to the motor another problem stood up... The motor startd rotating without the gate pulses which is not supposed to happen... after consulting with professors i removed the filter part of my circuit and removed the collector and emitter and connected just the gate of igbt but didnot apply the gate pulses and gave a 3phase supply and the motor didnot run which was right.... but when the collector and gate was removed and only emitter was connected and when the 3phase supply was given the motor started to rotate at 250v and that is supposed to happen... i tried changing the igbt(ct60 am 18b) and replaced with a mosfet (irf250n)... but the same result....please give me a solution ASAP in how to prevent the motor from rotating or if anything wrong in the connection i did.... so ryt nw in my circuit... a 3phase motor , rectifier, chopper circuit, the controller... theses are the main parts....



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    Re: Chopping of rectified dc voltage using IGBT ct60 am 18b

    Can you provide a project diagram you are using now?



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    Re: Chopping of rectified dc voltage using IGBT ct60 am 18b



    the first image represents the circuit diagram... but later few additional transistors were connected in the circuit which is shown in the second diagram......



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    Re: Chopping of rectified dc voltage using IGBT ct60 am 18b

    Try this way:



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    Re: Chopping of rectified dc voltage using IGBT ct60 am 18b

    Thanx alot!!! I will try it out and let u know the results.....



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