Question

A 250V, 4 pole , wave -wound d-c. series motor
has 782 conductors on its armature . It has armature and
series field resistance of 0.75 ohm. The motor takes a
current of 40 A. Estimate its speed and gross torque developed if it has a flux per pole of 25 mWb.
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Answer 1

Answer:

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Explanation:

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Answer 2

Given:  

The Voltage of the wave-wound DC motor $V=250$ $V$

Number of poles $P=4$

series field resistance=0.75 Ω

current $I$ $=40$ $A$

flux per pole$=25$ $mWb$

Number of conductors $Z$ $=782$

For wave winding $A=2$

 

To Find: Speed and gross torque

Solution:

Back emf

$E_{b}=V-I_{a}R_{a}$

$=250-40$×$0.75$

$=220$ $V$

Use the relation of back emf and speed

$E_{b}=$$\frac{NPZ}{60A}$×Ф

$N=\dfrac{220\times60\times2}{4\times782\times25mWb}$

$=338$ $rpm$

Torque developed is

τ$=0.159$Ф$ZI_{a}$$(P/A)$

$=0.159\times25\times10^{-3} \times782\times40\times\dfrac{4}{2}$

$=249$ $N-m$.

The speed and torque are $338$ $rpm$ and 249 $N-m$ respectively.