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    Four Quadrant Operation of DC Drives: - Dual Converters

    Uploaded by

    Dr.K.Krishna Veni
    The document discusses dual converter operation for four quadrant control of DC motors. A dual converter uses two similar converters connected in parallel to allow both positive and negative output voltage and current. This enables variable speed motor operation in both forward and reverse directions as well as forward and reverse braking. There are two modes of operation - non-circulating current where only one converter operates at a time, and circulating current where both converters operate simultaneously to eliminate harmonic circulating currents. Firing angles are controlled to achieve the desired output voltage and motor operation in each quadrant.

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    Four Quadrant Operation of DC Drives: - Dual Converters

    Uploaded by

    Dr.K.Krishna Veni
    628 views12 pages
    The document discusses dual converter operation for four quadrant control of DC motors. A dual converter uses two similar converters connected in parallel to allow both positive and negative output voltage and current. This enables variable speed motor operation in both forward and reverse directions as well as forward and reverse braking. There are two modes of operation - non-circulating current where only one converter operates at a time, and circulating current where both converters operate simultaneously to eliminate harmonic circulating currents. Firing angles are controlled to achieve the desired output voltage and motor operation in each quadrant.

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    Choppers

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    The document discusses dual converter operation for four quadrant control of DC motors. A dual converter uses two similar converters connected in parallel to allow both positive and negative output voltage and current. This enables variable speed motor operation in both forward and reverse directions as well as forward and reverse braking. There are two modes of operation - non-circulating current where only one converter operates at a time, and circulating current where both converters operate simultaneously to eliminate harmonic circulating currents. Firing angles are controlled to achieve the desired output voltage and motor operation in each quadrant.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    628 views12 pages

    Four Quadrant Operation of DC Drives: - Dual Converters

    Uploaded by

    Dr.K.Krishna Veni
    The document discusses dual converter operation for four quadrant control of DC motors. A dual converter uses two similar converters connected in parallel to allow both positive and negative output voltage and current. This enables variable speed motor operation in both forward and reverse directions as well as forward and reverse braking. There are two modes of operation - non-circulating current where only one converter operates at a time, and circulating current where both converters operate simultaneously to eliminate harmonic circulating currents. Firing angles are controlled to achieve the desired output voltage and motor operation in each quadrant.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 12

    Four Quadrant Operation of DC Drives

    -Dual Converters
    Dual Converter is a four Quadrant Converter –Output
    voltage /and output current is either Positive or negative
    Two similar converters -connected in parallel (inverse parallel )
    Four Quadrant Operation of DC Drives
    -Dual Converters
    By varying the , it is possible to  vary the output DC voltage as
    positive or negative

     2𝑉𝑚  
    𝐶𝑜𝑠 𝛼 3
    𝜋

    Using the dual converter we can have two modes of


    operations
    a) Variable speed motor in forward or reverse
    direction
    b) Reverse and forward braking of motor
    The Va, Ia plane for the dual converter is shown in fig
    Four Quadrant Operation of DC Drives
    -Dual Converters
    There are two modes of operation
    a)Non circulating current and
    b)Circulating current
     Non Circulating Current mode of Operation
    At any instant only one converter is in operation
    Converter A alone operates
    The current is always flow from x to y when the firing angle varied from
    0 to i.e (0<α<∏/2), the machine operates as motor in forward direction
    and the converter operates as rectifier

    When firing angle is between ∏/2 to ∏(∏/2< α< ∏), the machine
    operates in reverse braking mode(speed is reverse) and the converter
    operates as line commutated inverter.
    Four Quadrant Operation of DC Drives
    -Dual Converters
    There are two modes of operation
    a)Non circulating current and
    b)Circulating current
     Non Circulating Current mode of Operation
    At any instant only one c converter is in operation
    Converter B alone operates
    The current is always flow from y to x, when the firing angle varied from
    0 to i.e (0<αB<∏/2), the machine operates as motor in reverse direction
    and the converter B operates as rectifier

    When firing angle is between ∏/2 to ∏(∏/2< αB < ∏), the machine
    operates in forward braking mode and the converter B operates as line
    commutated inverter.
    Four Quadrant Operation of DC Drives
    -Dual Converters
    a)Non circulating current
    Four Quadrant Operation of DC Drives
    -Dual Converters
    a)Non circulating current
    When the direction of the rotation of the motor is to be reverse,
    it is required to see that that the first converter is turned off and
    the motor has attained zero speed and then current becomes
    zero. Afterwards the second converter is made to operate by
    giving suitable signals to gate. To achieve this current is to be
    sensed and also a small time interval is required for the change
    over of the rectifier.
    Four Quadrant Operation of DC Drives
    -Dual Converters
    b)Circulating current  
    Converter A and B will be in operation simultaneously. On the DC side,

    Cos = - Cos
    . = Cos(- )
    + =
    =-
    Firing angles of converter A and B are controlled such that the average DC
    output voltages at x and Y due to converter A and B be should be the same
    value.
    For achieving this if =
    Current limiting rector(usually 30% of the rated current) used to
    eliminate the circulating current of harmonic frequencies
    Four Quadrant Operation of DC Drives
    -Dual Converters
    Case I: I, II quadrant operation:  
    Converter A firing angle is varied from 0 to and B firing angle from to
    Four Quadrant Operation of DC Drives
    -Dual Converters
    Case I: III, IV quadrant operation:
     
    Converter B firing angle is varied from 0 to and A
    firing angle from to
    Four Quadrant Operation of DC Drives
    -Dual Converters
    Four Quadrant Operation of DC Drives
    -Dual Converters
    Four Quadrant Operation of DC Drives
    -Dual Converters
    A 220V 1500 rpm, 50A separately excited motor has an armature resistance of
    0.5ohms. Armature is fed from a3 phase circulating current mode dual converter
    consisting of fully controlled converters A and B. Rectifier A provides the motoring
    operation in the forward direction and B in reverse direction. Line voltage is 165V.
    Calculate firing angle of A and B for
    i)Motoring operation at rated torque and 1000rpm
    ii)Regenerative braking operation at rated torque and 1000rpm.
    iii)Motoring operation at rated torque and -1000rpm
    ii)Regenerative braking operation at rated torque and -1000rpm.

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