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DC Motor Armature Voltage

DC motor armature voltage is the voltage applied across the armature (the rotating part) of a direct current (DC) motor.  The armature is typically a coil of wire wound around a core that sits within a magnetic field created by the motor's field windings or permanent magnets.  This voltage is used to determining the motor's performance, including its speed and torque.

DC Motor Armature Voltage Formula

\(  V_a \;=\;  E_b  +  I_g  \cdot  R_a  \)     (DC Motor Armature Voltage)

\(  E_b \;=\;  V_a  -  I_g  \cdot  R_a  \)

\(  I_g \;=\;   \dfrac{ V_a  -  E_b }{   R_a  }\)

\(  R_a \;=\;   \dfrac{ V_a  -  E_b }{   I_g  }\)
Symbol English Metric
\( V_a \) = Armature Voltage \(V\) \(V\)
\( E_b \) = Back EMF \(V\)  \(V\)
\( I_a \) = Armature Current \(A\) \(A\)
\( R_a \) = Armature Resistance \(\Omega\) \(\Omega\)
It causes current to flow through the armature resistance, producing a magnetic field that interacts with the stator's magnetic field to generate rotational motion.  It also counteracts the back electromotive force induced in the armature due to its rotation in the magnetic field.  In a DC motor, the speed is largely influenced by the armature voltage.  Increasing typically increases the motor speed, assuming a constant load, because (and thus speed) adjusts to balance the equation.  Armature voltage is controlled using external circuits like variable resistors, choppers, or pulse-width modulation in modern systems to regulate motor behavior.
 
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DC Motor Armature Voltage Formula

  • In electrical engineering, the speed of rotor is directly proportional to armature voltage. While designing DC motor to attain a certain speed, it's essential to calculate the the armature voltage as it controls the speed.

\(  V_a \;=\;  K_a  \cdot  n \cdot  \Phi_B  \)     (DC Motor Armature Voltage)

\(  K_a \;=\;  \dfrac{ V_a  }{  n \cdot  \Phi_B  }\)

\(  n \;=\;  \dfrac{ V_a  }{  K_a  \cdot  \Phi_B  }\)

\(  \Phi_B \;=\;  \dfrac{ V_a  }{  K_a  \cdot  n  }\)
Symbol English Metric
\( V_a \) = Armature Voltage \(V\) \(V\)
\( K_a \) = Motor Constant (Depends on the Design) - -
\( n \) = Motor Speed \(RPM\) \(RPM\)
\( \Phi_B \)  (Greek symbol Phi) = Armature Magnetic Flux \(Wb\) \(Wb\)

 

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