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    Experiment: Measurement of Power in Three Phase Balanced Load

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    Tripti Gupta
    The document describes an experiment to measure power in a three-phase balanced load using two wattmeter methods. Key points: 1) The experiment aims to determine the relationship between phase/line voltages and currents as well as power and power factor measurements. 2) Equipment includes a voltmeter, ammeter, three-phase transformer, balanced R-L load and two wattmeters. 3) For a balanced three-phase circuit, total power is calculated as the sum of the readings on the two wattmeters. The power factor can then be derived.

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    Experiment: Measurement of Power in Three Phase Balanced Load

    Uploaded by

    Tripti Gupta
    153 views2 pages
    The document describes an experiment to measure power in a three-phase balanced load using two wattmeter methods. Key points: 1) The experiment aims to determine the relationship between phase/line voltages and currents as well as power and power factor measurements. 2) Equipment includes a voltmeter, ammeter, three-phase transformer, balanced R-L load and two wattmeters. 3) For a balanced three-phase circuit, total power is calculated as the sum of the readings on the two wattmeters. The power factor can then be derived.

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    experiment 5

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    The document describes an experiment to measure power in a three-phase balanced load using two wattmeter methods. Key points: 1) The experiment aims to determine the relationship between phase/line voltages and currents as well as power and power factor measurements. 2) Equipment includes a voltmeter, ammeter, three-phase transformer, balanced R-L load and two wattmeters. 3) For a balanced three-phase circuit, total power is calculated as the sum of the readings on the two wattmeters. The power factor can then be derived.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    153 views2 pages

    Experiment: Measurement of Power in Three Phase Balanced Load

    Uploaded by

    Tripti Gupta
    The document describes an experiment to measure power in a three-phase balanced load using two wattmeter methods. Key points: 1) The experiment aims to determine the relationship between phase/line voltages and currents as well as power and power factor measurements. 2) Equipment includes a voltmeter, ammeter, three-phase transformer, balanced R-L load and two wattmeters. 3) For a balanced three-phase circuit, total power is calculated as the sum of the readings on the two wattmeters. The power factor can then be derived.

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    EXPERIMENT: MEASUREMENT OFPOWER IN THREE PHASE BALANCED LOAD.

    Objective: To determine: (1) Relationship between phase and line voltage and current

    (2) Power and power factor by two wattmeter method.

    Equipment: (1) Voltmeter: 150V, AC (2) Three phase balanced R-L Load (3) C-M Board
    (4) AC Ammeter: 3 Amp (5) Three phase transformer (6) Wattmeter: 125V/5A

    PLUG 3PHA SE 230 V

    AR CAT
    W

    82 b2
    2R1
    3PHASE230 V SW FUSE
    CR
    c22 C.M. BOARD R2

    Y L2
    B

    Circuit diagram
    Theory:
    Power measurement: The active power per phase in three
    is the phase angle between phase voltage and
    phase circuit is given by P=V,l,Cos6 Where
    phase current.V, is phase voltage and I, is phase
    current.Total power in three phase circuit is given by P=3 V, 1, Cos 0.
    For star connections, V,=(V/W3) and I,= LP = 3(V/V3)( IL) Cos = N3 V, I,Cos .

    For delta connections V,=V. and I, =(LV3). P =3 V.( LN3)Cos 0 = v3 V, I, Cos 0


    L is the line current and Vi is the line voltage.
    Power and power factor in a three phase balanced circuit is measured
    by one wattmeter or two
    wattmeter or three wattmeter method. Three wattmeter methods is uscd to measure power in
    unbalanced circuit.
    For wattmeter Wi, the current through current coil is la and voltage across potential coil is (Va-Vb).
    For watt meter W, the current through current coil is Ic and voltage across potential coil is (Vc-Vb)
    Total instantaneous power of load =
    Vala+V l+Vclc.

    Now.considering the three phase balanced load:


    Sum of all the three phase currents is zero,i.e I,+I,+ I=0 for balanced circuit,
    So total
    instantaneous power P (V,-V.) la +
    =

    (Ve-V,) Ic
    P Instantaneous
    reading of W,+ Instantaneous
    reading of W2
    Using phasor diagram, W, 13(VLX L) Cos (30° and
    =

    +0) W, =
    V3v, I, Cos (30° -0)
    Such that power in 3
    phase circuit will be W=W+W=V3
    load. (V)MCos 0, Where 0 is the phase angle of
    Hence power=P=W=W+W=V3 (V)(NCos.
    The Power factor
    can be calculated as: cos =
    cos [tan' {V3 (W-W,)/(W+W,)}]|
    Procedure:
    Connect the
    experimental set up as shown in the circuit diagram.
    Switch on the appropriate input
    supply and measure the following,
    Voltage across each phase (b) Voltage betvween line terminals
    (C) Voltage across Rand L.(d)
    Current in each phase by using the current measurement board.
    Power: Wattmeter (W): keeping switch 1-2 open and closing switches 3-4& 5-6 closes.
    (W): keeping switch 3-4 open and closing switches 1-2 &5-6 closed.
    Record readings of all the instruments in the observations in table.
    Observation:
    Type of Voltage (V)
    Circuit
    Current V..L/A, Wattmeter Total Powe
    (A) Readings Power Facte
    Vp V V. V W W P=W+W Cos E
    STAR
    Report
    >Discuss the discrepancies between calculated and
    measured values.
    Sketch the phasor diagràm in each case and calculate
    reading of each watt meter.
    Explain how sometimes a wattmeter reads negative reading in three phasc measurement.
    Quiz questions:
    1. The power taken by a three phase balanced load is given by.
    2. The lcast number of
    single phase watt meters required to mcasure total power consumed
    unbalanced load feed from a three phase, four wire by an
    system is .

    3. In two-wattmeter method of
    measuring three-phase power, one of the wattmeter shows
    What will be the value of
    power factor in this case?
    zero reading.
    4. If the power consumed
    per phase by star connected balanced load is 200W, what will be the power
    consumed per phase if the same load is connected in delta?

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