PLEASE HELP ME TO SOLVE NUMBER 4 4The armature current of a series motor is 60 A when on full-load. If the load is adjusted to thatthis current decreases to 40 A, find the new torque expressed as a percentage of the full-loadtorque. The flux for a current of 40 A is 70% of that when the current is 60 A.[46%]5 A 4-pole, d.c. shunt motor has a flux per pole of 0.04 Wb and the armature is lap-wound with 720conductors. The shunt field resistance is 240 Q and the armature resistance is 0.2 Q. Brush contactdrop is 1 V per brush. Determine the speed of the machine when running (a) as a motor taking 60A and (b) as a generator supplying 120 A. The terminal voltage in each case is 480 V.[972 r.p.m.; 1055 r.p.m]A 25-kW shunt generator is delivering full output to 400-V bus-bars and is driven at 950 r.p.m. by beltdrive. The belt breaks suddenly but the machine continues to run as a motor taking 25 kW from thebus-bars. At what speed does it run? Take armature resistance including brush contact resistance as6.0.5 Q and field resistance as 160 Q.[812.7 r.p.m.]

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Answered: The armature current of a series motor…

The armature current of a series motor is 60 A when on full-load. If the load is adjusted to that this current decreases to 40 A, find the new torque expressed as a percentage of the full-load

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter5: Resistors

Section: Chapter Questions

Problem 1PA

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Question

PLEASE HELP ME TO SOLVE NUMBER 4

4
The armature current of a series motor is 60 A when on full-load. If the load is adjusted to that
this current decreases to 40 A, find the new torque expressed as a percentage of the full-load
torque. The flux for a current of 40 A is 70% of that when the current is 60 A.
[46%]
5 A 4-pole, d.c. shunt motor has a flux per pole of 0.04 Wb and the armature is lap-wound with 720
conductors. The shunt field resistance is 240 Q and the armature resistance is 0.2 Q. Brush contact
drop is 1 V per brush. Determine the speed of the machine when running (a) as a motor taking 60
A and (b) as a generator supplying 120 A. The terminal voltage in each case is 480 V.
[972 r.p.m.; 1055 r.p.m]
A 25-kW shunt generator is delivering full output to 400-V bus-bars and is driven at 950 r.p.m. by belt
drive. The belt breaks suddenly but the machine continues to run as a motor taking 25 kW from the
bus-bars. At what speed does it run? Take armature resistance including brush contact resistance as
6.
0.5 Q and field resistance as 160 Q.
[812.7 r.p.m.]

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