Question

A $230 \mathrm{~V}$ dc series motor draws a line current of $60 \mathrm{~A}$ when running at a rated speed of 600 rpm. $R_a=0.12 \Omega$ and $R_s=0.08 \Omega$. Determine the speed of the motor when the line current drops to $30 \mathrm{~A}$ and the no-load speed of the machine for a line current of $3.2 \mathrm{~A}$.

   A $230 \mathrm{~V}$ dc series motor draws a line current of $60 \mathrm{~A}$ when running at a rated speed of 600 rpm. $R_a=0.12 \Omega$ and $R_s=0.08 \Omega$. Determine the speed of the motor when the line current drops to $30 \mathrm{~A}$ and the no-load speed of the machine for a line current of $3.2 \mathrm{~A}$.

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Essentials of Electrical and Computer Engineering

Essentials of Electrical and Computer Engineering

David V. Kerns, Jr.,… 1st Edition

Chapter 15, Problem 30

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Step 1

The voltage equation for a DC motor is given by: \[ V = E + I_a R_a + I_s R_s \] Where: - \( V \) = supply voltage = 230 V - \( I_a \) = armature current = line current = 60 A (since it's a series motor) - \( R_a \) = armature resistance = 0.12 Ω - \( R_s \) = Show more…

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A $230 \mathrm{~V}$ dc series motor draws a line current of $60 \mathrm{~A}$ when running at a rated speed of 600 rpm. $R_a=0.12 \Omega$ and $R_s=0.08 \Omega$. Determine the speed of the motor when the line current drops to $30 \mathrm{~A}$ and the no-load speed of the machine for a line current of $3.2 \mathrm{~A}$.

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