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    Speed Control of DC Motor

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    jitbak
    This document describes an experiment to study the effect of speed control methods for a DC motor. The two methods tested are: 1. Variation of armature voltage with constant field excitation. Speed increases with increasing armature voltage. 2. Variation of field current (excitation) with constant armature voltage. Increasing field current increases the flux in the motor, which increases speed. The experiment involves connecting a DC motor to a power supply and instruments to measure voltage, current, and speed. Speed is recorded at various voltage and current levels to analyze the relationships between excitation, applied voltage, and motor speed.

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    Speed Control of DC Motor

    Uploaded by

    jitbak
    80 views4 pages
    This document describes an experiment to study the effect of speed control methods for a DC motor. The two methods tested are: 1. Variation of armature voltage with constant field excitation. Speed increases with increasing armature voltage. 2. Variation of field current (excitation) with constant armature voltage. Increasing field current increases the flux in the motor, which increases speed. The experiment involves connecting a DC motor to a power supply and instruments to measure voltage, current, and speed. Speed is recorded at various voltage and current levels to analyze the relationships between excitation, applied voltage, and motor speed.

    Original Description:

    How to perform speed control of dc

    Original Title

    Speed control of DC motor

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    This document describes an experiment to study the effect of speed control methods for a DC motor. The two methods tested are: 1. Variation of armature voltage with constant field excitation. Speed increases with increasing armature voltage. 2. Variation of field current (excitation) with constant armature voltage. Increasing field current increases the flux in the motor, which increases speed. The experiment involves connecting a DC motor to a power supply and instruments to measure voltage, current, and speed. Speed is recorded at various voltage and current levels to analyze the relationships between excitation, applied voltage, and motor speed.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    80 views4 pages

    Speed Control of DC Motor

    Uploaded by

    jitbak
    This document describes an experiment to study the effect of speed control methods for a DC motor. The two methods tested are: 1. Variation of armature voltage with constant field excitation. Speed increases with increasing armature voltage. 2. Variation of field current (excitation) with constant armature voltage. Increasing field current increases the flux in the motor, which increases speed. The experiment involves connecting a DC motor to a power supply and instruments to measure voltage, current, and speed. Speed is recorded at various voltage and current levels to analyze the relationships between excitation, applied voltage, and motor speed.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    of 4

    Expt.

    4 Speed control of DC motor


    Aim : To Study the effect on speed of

    a) Variation of field current ( excitation) with constant armature voltage


    b) Variation of armature voltage with constant excitation.
    Apparatus :

    1. DC Shunt Motor (1 HP,220 v,3.4 A, 1500RPM)


    2. DC voltmeter(0-300)V
    3. DC Ammeter(0-1)A
    4. Rheostat(76Ω,1.2A, 760Ω,1.5A)
    5. Tachometer(0-5000RPM)
    6. Connecting wires.

    Theory :

    For DC machine the induced emf( back emf) Eb is given by

    Eb = (ø Z N P/ 60 A)
    Where,
    P = no of poles
    Z = no of Armature conductors
    A = no of parallel paths on armature
    N = speed in rpm
    N α Eb / ø

    Now
    Eb = V- Ia Ra for a DC motor where
    V = Armature voltage
    Ra = Armature resistance
    Ia = armature current
    N α (V- Ia Ra) / ø
    As the value of armature resistance is very small, the drop Ia Ra is very small
    NαV /ø
    Thus the factors affecting the speed of a DC motor are,
    1. The flux ø
    2. The voltage across the armature
    3. The applied voltage , So The speed can be controlled
    1. Changing the flux by controlling the current through the field winding.(Flux control)

    2. Changing the armature path resistance which changes the voltage applied across the
    armature. This is rheostatic control.

    3. Changing the applied voltage called voltage control method.

    Procedure:

    A] Speed variation by Armature voltage control with constant field current

    1. Connections are made as shown in fig.

    2. With full excitation a low rating voltage is applied.

    3. Voltage is increased gradually in steps noting down the speed and keeping
    excitation constant

    4. Plot the graph of speed (N) Vs Armature voltage(V).

    5. Note down values of Field current and speed.

    6. Plot the graph of speed (N) in rpm Vs field current(If) in A.


    7. Observe the change of direction by interchanging either armature terminals or by
    interchanging field terminals.

    B] Speed variation by field current control with constant Armature voltage.

    1. Connections are made as shown in fig.

    2. The rheostat in field current is kept at minimum so that motor starts with full
    excitation and hence with good starting torque.

    3. The value of resistance in the field circuit is increased gradually so that speed of
    motor is increased.

    4. The voltage applied to armature is kept constant throughout this part of experiment.

    Observation Table:

    A] Constant Field Current = If =

    Sr.No. Armature Voltage V (Volts) Speed N

    (rpm)

    B] Constant Armature Voltage = V =

    Sr.No. Field Current If (Amp) Speed N

    (rpm)
    Expected Graphs

    Conclusion:

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