Ad.c. series motor connected to a 235 V supply takes 43 A at 950 r.p.m.The armature resistance is 0.16 Q and the field resistance is 0.13 0. If thetorque for a second case is 194.63 N.m and the back emf for the secondcase is 213.85 v. How many % should the motor speed decreased to ascompared to the rated speed?

Given: DC series motor To find:

A d.c. series motor connected to a 235 V supply takes 43 A at 950 r.p.m. The armature resistance is 0.16 Q and the field resistance is 0.13 Q. If the torque for a second case is 194.63 N.m and the back emf for the second case is 213.85 v. How many % should the motor speed decreased to as compared to the rated speed?

A d.c. series motor connected to a 235 V supply takes 43 A at 950 r.p.m. The armature resistance is 0.16 Q and the field resistance is 0.13 Q. If the torque for a second case is 194.63 N.m and the back emf for the second case is 213.85 v. How many % should the motor speed decreased to as compared to the rated speed?

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

See similar textbooks

Similar questions

6) a) A Series motor takes a current of 20 A when the supply voltage is 230V. If the total resistance of the motor is 2 Ω and the Iron, Friction, Windage losses are 100 W. Find the efficiency of the motor. b) In DC motor, Back emf is less than Supply voltage. Justify
The speed of a 230 V shunt motor is to be reduced from 900 r.p.m to 600 r.p.m. The resistance of the armature circuit is 0.3 ohm. When the motor current is 30 A, speed is 900 r.p.m. If the current reduces to 20 A at lower speed, what arrangement should be made? Neglect any effect not included in the data given.
On no-load, a shunt motor takes 5 A at 250 V, the resistances of the field and armature circuits are 250 Ω and 0.1 Ω respectively. Calculate the output power and efficiency of the motor when the total supply current is 81 A at the same supply voltage. State any assumptions made.
A dc series motor drives a load a 30rev/s and takes a current of 10A when the supply voltage is 400V. If the total resistance of the motor is 2ohms and the iron, friction and windage losses amount to 300W, determine the efficiency of the motor.
A D.C. series motor when loaded to 50 A runs at 1500 r.p.m. on a 220 V supply. Themotor resistance is 0.1 ohm and the flux may be taken as proportional to the current.Calculate the value of resistance to be inserted in series to bring down the speed to900 r.p.m. at which the load torque is hakf the previous value.(Ans.3.544 ohms)
A dc shunt motor operating at an armature terminal voltage of 125 V is observed to be operating at a speed of 1180 r/min. When the motor is operated unloaded at the same armature terminal voltage but with an additional resistance of 5Ω in series with the shunt field, the motor speed is observed to be 1250 r/min. i. Calculate the resistance of the series field. ii. Calculate the motor speed which will result if the series resistance is increased from 5Ω to 15Ω.
A 10-hp (7.46 kW), 250-V. shunt motor takes a line current of 5 A. when runninglight. Calculate the efficiency when delivering full load output, if the armature andfield resistances are 0.5 Ω and 250 Ω respectively. At what output power will theefficiency be maximum?
A 200 V D.C. shunt motor takes 20 A at rated voltage and runs at 1000 r.p.m. Itsarmature resistance is 0.1 ohm. Calculate the value of additional resistance requiredin the armature circuit to reduced the speed to 800 r.p.m when the load torque isindependent of the speed.Ignore the field current. (Ans.1.98 ohm)
The speed of a 230 V shunt motor is to be reduced from 900 r.p.m to 600 r.p.m. Theresistance of the armature circuit is 0.3 ohm. When the motor current is 30 A, speedis 900 r.p.m. If the current reduces to 20 A at lower speed, what arrangement shouldbe made? Neglect any effect not included in the data given. (Ans.3.833 ohms)
A dc shunt motor rated at 250V, runs at 1000rpm draws a current of 25A. Determine the speed if the field is weakened by 3% for the line current of 50A. The armature and field resistances are 0.2 and 250 ohms respectively. Brush drop may betaken as 1V per brush.
8.) 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 busbars. At what speed does it run ? Take armature resistance including brush contact resistance as 0.5 Ω and field resistance as 160 Ω.
A dc series motor operates at its full rated load at 1500 rpm. The line condition are 125 V and 10 A. The motor has an armature circuit resistance, including the commutating field, of 1.25 ohms and a series field resistance of 0.425 ohms . Assuming that the field flux changes linearly with field current, what will be the motor speed if the load is such that the line current drops to 6.25 A?