1 Name the losses in a dc motor.2 What causes iron losses and how can they bereduced?-3 Explain why the temperature of a machineincreases as the load increases.

Step 1: (1). Losses in a DC Motor: The losses in a DC motor can be categorized into the following…

Answered: 1 Name the losses in a dc motor. 2 What…

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...

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A 220 V DC series motor runs drawing a current of 30 A from the supply. Armature and field circuit resistances are 0.4 and 0.1 respectively. The load torque varies as the square of the speed. The flux in the motor may be taken as being proportional to the armature current. To reduce the speed of the motor by 50% the resistance in ohms that should be added in series with the armature is
The resistance of the field winding(copper wire) of a DC machine is 0.25 ohm at 25°C. When operating at full-load, the temperature of the winding is 75 °C. The temperature coefficient of resistance of copper is 0.00427 per °C at 0°C. Find the resistance of the field winding at full-load.
Q4-A d.c. series motor runs at 500 r. p.m. on 220V supply drawing a current of 50A .The total resistance of the machine is 0.15 Q2,calculate the value of the extra resistance to be connected in series with the motor circuit that will reduce the speed to 300 r.p.m. The load torque being then half of the previous value. Assume flux proportional to current.
A 240-volt series motor has an armature resistance of 0.42 ohm and a series-field resistance of 0.18 ohm. If the speed is 500 rpm when the current is 36 A, what will be the motor speed when the load reduces the line current to 21 A? (Assume a 3-volt brush drop and that of the flux is proportional to the current.). Ans.: 1435 rpm show diagram and step by step process
Please try to solve
A 230 V dc series motor has an armature resistance of 0.2 ohm and field resistance of 0.1 ohm at rated voltage. The motor draws a line current of 40 amperes and runs at a speed of 1000 rpm. Find speed of the motor for line current of 20 A at 230 V. Assume that flux at 20 A line current is 60% of flux at 40 A line current.
Q4/B/ What are the principal characteristics of a series DC motor? What are its uses? Core Mc
Q1. (A)- A series DC motor runs at 600 r.p.m drawing a current of 52A when connected to 220 V supply. The total resistance of the machine is 0.14 2. Calculate the value of the external resistance to be connected in series with the motor circuit to reduce its speed to 400 r.p.m. Assume the load torque is decreased to half of the previous value. Consider the field flux is proportional to armature current.
a dc shunt motor runs at 900 r.p.m from a 460 V supply when taking an armature current of 25 A. Calculate the speed at which it will run from a 230 V supy when taking an armature current of 15 A . The resistance of the armature circuit is 0.8 ohms . Assume the flux per pole at 230 V to have decreased to 75 % of its value at 460 V .
Q4) A 460-V series motor runs at 500 r.p.m. taking a current of 40 A. The total resistance of the armature and field circuits is 0.8 Q. If the load is reduced so that the motor is taking 30 A, and assuming the flux is proportional to the field current, calculate: (a) the speed and (b) percentage change in torque.
A brushed DC motor has a permanent magnetic field of 1.3 T. The armature radius is 0.05 m. The current flowing through the windings is 2.4 A and this produces a torque of 0.14 Nm. Determine the length of the windings in the machine in m.
1 Name three types of dc motors and make a sketch of the connections.

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1 Name the losses in a dc motor. 2 What causes iron losses and how can they be reduced? -3 Explain why the temperature of a machine increases as the load increases.