Question

Draw the speed-torque characteristics of a DC shunt motor. Write
the expression for speed

torque relation

Answer #1

a)Explain the shunt excitation and compound excitation of DC
generator.
b)A 240V compound DC motor has the armature, series field and
shunt field resistances are
0.22 Ω, 0.04 Ω and 200 Ω respectively. On full load, the line
current is 17.5 A and the motor runs at 1800 rpm. (short
shunt)
i) Draw the diagram and the power flow of the motor.
ii) Find the back EMF of the motor.
iii) Find the mechanical power developed.
iv) Find the output...

A 25-hp, 240V, DC shunt motor has
armature and field resistances of 0.2 ? and 120 ?, respectively. At
no load and rated voltage, the motor draws a line current of 5A and
its speed is 1250 rpm.
When driving a certain load, the
input to the motor is 15KW. For this condition, find:
a.The speed of the motor
b.The developed torque
The efficiency of the motor at this load

Q3: (a) Determine the terminal voltage of a dc shunt generator
which develops an e.m.f. of 240V and has an armature current of 50
A on load. Assume the armature resistance is 0.04Ω. [3 marks]
(b) A lap wound armature is used in a 4-pole dc machine and 70
coils on the armature each containing 10 turns. The flux per pole
in the machine is 40 mWb and the machine rotates at 500 rpm; (a)
How many current paths are...

A 100 hp, 250 V, 1200 rpm DC shunt motor
with an armature resistance of 0.03 ? and a field
resistance of 41.67 ?. The motor has compensating
windings, so armature reactance can be ignored.
Mechanical and core losses may be ignored also. The
motor is driving a load with a line current of 126 A and
an initial speed of 1103 rpm. The magnetization curve is
shown in the following figure.
1. What is the motor speed if the...

A 200 V DC, 1,800 RPM shunt connected motor has an armature
resistance of 0.4 ohm and a brush resistance of 0.4 ohm; brush
voltage drop of 6.0 V, independent of load. The resistance of the
shunt field is 230 ohm. The full load rated line current is 40 A.
When the motor is operated at no load the line current is 5 A and
the speed is 1750 RPM.
Calculate speed at rated load
Calculate speed at .3 rated...

The full-load armature current of a 5 hp, 150 V shunt dc motor
is 30 A. The field (shunt) resistance and the armature resistance
of the motor are ????F = 125 ? and ???????? = 0.15, respectively.
At a random speed of 1800 rpm magnetization curve of the motor has
measured and is shown in the table below. ????0 (V) armature
voltage 10 90 110 140 170 185 ???????? (A) field (shunt) current 0
0.82 1 1.2 1.7 2.88 Calculate...

Question 2
The full-load armature current of a 5 hp, 150 V shunt dc motor
is 30 A. The field (shunt) resistance and the armature resistance
of the motor are ????F=125 ? and ????????=0.15, respectively. At a
random speed of 1800 rpm magnetization curve of the motor has
measured and is shown in the table below.
EO(V) armature voltage
10
90
110
140
170
185
IF (A) field (shunt) current
0
0.82
1
1.2
1.7
2.88
Calculate the following:
a....

A 230-V DC shunt motor has armature circuit resistance of 0.25 ?
and field circuit resistance of 115 ?. At
full load armature draws a current of 38 A and the speed is
measured at 1050 rpm. Find the developed
torque.
The field rheostat is now changed so that total field resistance is
144 ?. Find the speed under this condition.
Assume that the armature current does not change. Assuming the
rotational losses amount to 600 W, find the
efficiency...

Design of DC Motor Starter
In order for a dc motor to function properly, it must be protected
from physical
damage during the starting period. At starting conditions, the
motor is not rotating,
and armature generated voltage EA = 0 V. Since the internal
resistance of a normal DC
motor is very low, a very high current flows. It is possible for a
motor to be severely
damaged by such currents, even if they last for only a moment.
A...

Design of DC Motor Starter In order for a dc motor to function
properly, it must be protected from physical damage during the
starting period. At starting conditions, the motor is not rotating,
and armature generated voltage EA = 0 V. Since the internal
resistance of a normal DC motor is very low, a very high current
flows. It is possible for a motor to be severely damaged by such
currents, even if they last for only a moment. A...

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