Open windings 2. 3. 9. Brush troubles may arise due to the insufficient contact surface, too short brush, too little spring tension or wrong brush setting. This DC Electrical Circuits Workbook, by James M. Fiore is copyrighted under the terms of a Creative Commons license: This work is freely redistributable for non-commercial use, share-alike with attribution Published by James M. Fiore via dissidents ISBN13: 978-1796779035 For more information or feedback, contact: James Fiore, Professor 2. A representation of the functional block diagram is shown in Figure 1.

3. 130 TOP D.C.MOTOR Questions and Answers pdf. (b) field diverter method. Non-salient rotor for a synchronous machine MODULE-III (10 HOURS) Three phase Induction Motor: Construction and principle of operation, types; Slip- Transmission of electrical energy covered longer distances at a lower loss with alternating current. Given that Ta2 /T a1 =Ia1 /Ia2; N2/N 1=E b2 /E b1 Eb=V a-IaRa. Problem 1 Separately Excited DC Motor [. The input to a dc-dc converter is an unregulated dc voltage Vg. Both these problems can be solved for one unknown at a time, without messy algebra. The input parameters are the supply voltage ( E) and the supply current ( I) and the output mechanical parameters are the torque ( T) and the rotational speed (). An electric motor is an electrochemical device that converts electrical energy into mechanical energy. Problem set 1 (PDF) Solutions to problem set 1 (PDF) Problem set 2 (PDF) Solutions to problem set 2 (PDF) A Compendium of Lamination Steel Alloys Commonly Used in Electric Motors. Now torque T c = f c. r = BLI a .r/A. Dc/dc converters form an integral part of many power distribution systems. QUESTIONS: 1.

The resulting torque-speed characteristic of a shunt dc motor is shown in fig.8.7: Speed n o n Torque T d Fig, 8.7 Speed - torque characteristic of a shunt or separately excited dc motor. Fuse or circuit breaker is tripped. In armature controlled DC motor the desired speed is obtained by varying the armature voltage. DC Motor/Generator module to demonstrate and explain the operation of dc motors and generators Operating principle of dc motors As stated in Unit 1, motors turn because of the interaction between two magnetic fields. Several troubles may arise in a DC motor. A few of them are discussed below: excessive load. excessive load. Brush troubles may arise due to the insufficient contact surface, too short brush, too little spring tension or wrong brush setting. Commutator troubles may be due to dirt on the commutator, high mica, rough surface or eccentricity.

2. [5+5] 3. a) What are the various factors that influence the choice of electric drives ? C Basic and Practical Skills Solving Problems and Critical Thinking C.01 Identify the problem. Most electric motors operate through the interaction of magnetic field and current carrying conductors to generate force. Q1. Simple DC circuits problems and solutions. N 1 = 750. 1. Analogue comparator may be used. To begin with few problems on d.c motors have been solved and then problems on generator are taken up. Stator: the stationary part of the motor. To reduce the copper losses. 3. For any queries regarding the NPTEL website, availability of courses or issues in accessing courses, please contact. For each reading in Parts I, II and III above, calculate the following: (a) Motor input power, (b) Motor copper loss, (c) Motor converted power, (e) Motor torque. 1. DC motors are widely used to drive various equipment.

Don't worry about the colors. 11. The field resistance is R, and the armature resistance is negligible. Q1. UNIT-III DC MOTORS AND TESTING: Principle of Direct current Machines, Longman higher education, 1st edition, 1985. problems on AC motors.

15. 2.The alternator voltage must be in phase with the grid system. DC Motors direct-drive vs. gearhead built-in gears or not voltage what voltage it best operates at current (efciency) how much current it needs to spin speed how fast it spins torque how strong it spins oh, and also: size, shaft diameter, shaft length,etc. Answer: A. The total armature resistance is 0.221 . From the above definition, we can conclude that any electric motor that is operated using direct current or DC is called a DC motor.

Find: a.) List the types of armatures used in dc generators. State the term that applies to voltage variation from no-load to full-load conditions and how it is expressed as a percentage. DC Motor Braking: Rheostat or Dynamic Braking If the armature winding of a dc motor is suddenly disconnected from the source, the motor will coast to a stop. List the essential parts of a DC generator. E b = k f . 30.1 V Field Rheostat. Following Electrical Engineering Multiple choice objective type questions and answers will help you in BSNL JTO, GATE 2021 and IES 2021 examinations : The direction of force can be found by left hand rule. This article will help you troubleshoot six of the most common DC motor issues. 3/23/2007 ELEC A6 DC Machine 2 DIRECT CURRENT (DC) MACHINES Fundamentals Generator action: An emf (voltage) is induced in a conductor if it moves through a magnetic field. The resulting torque-speed characteristic of a shunt dc motor is shown in fig.8.7: Speed n o n Torque T d Fig, 8.7 Speed - torque characteristic of a shunt or separately excited dc motor. 2 = 90% 1. A 230 V d.c. shunt motor runs at 800 r.p.m. R 1 > R 4. Most stator faults are caused by insulation breakdown which leads to winding failure. Based on the figure below, determine the electric current through R1. In case of a brushed DC motor, feedback is implemented using a mechanical commutator and brushes. R a = 0.25. A wound rotor (rotating field) which has the same number of poles as the stator, and is supplied by an external source of 130 TOP D.C.MOTOR Questions and Answers pdf. 9 Separately-excited DC machine circuit in motoring mode Ea Kg f m 2 a pC K a g p: number of poles Ca : total number of conductors in armature winding a: number of parallel paths through armature winding Ea Vt Te produces rotation (Te and m are in the same direction) Pmech 0, Te 0 and m 0 output power produced friction and windage 1. of poles = 4, Z = 600, Wave Met by research and preparation prior to group discussion. Determine (a) the value of rotational losses and (b) the efficiency. (SSC 2018 -S-1) Ques.3. This article will help you troubleshoot six of the most common DC motor issues. Working Principles and Operation. Threading results in fine lines on the surface of your commutator. What is a DC Motor? Brushless motors work differently from your usual positive/negative DC equipment.-----Motor Runs Backwards? problems on AC motors. Find the input power and efficiency of a DC generator supplying a load of 35 A at an output voltage of 200 V. The losses are as follows: friction 250 W, iron 125 W, field 200 W, armature copper losses 490 W, other stray losses 85 W. DC Motor Efficiency. In the DC machine, the fractional pitch winding is used. 6 1. The Physics of the DC Motor current in the single loop can be reversed (commutated) every half turn to keep the torque constant. 1.2.1 Torque Production Consider the magnetic system in Figure 1.4, where a cylindrical core is cut out of a block of a permanent magnet and replaced with a soft iron core. (SSC 2018 -S-1) The equivalent resistance in series combination is larger than the largest resistance in Calculate the speed if the torque is doubled. For each reading in Parts I, II and III above, calculate the following: (a) Motor input power, (b) Motor copper loss, (c) Motor converted power, (e) Motor torque. 3.The alternator frequency must be the same as the grid system frequency. -The single -phase full bridge inverter shown below is operated in the quasi square wave mode at the frequency f = 50 Hz with a phase-shift of = 2/3 between the half-bridge outputs v ao and v bo. The emf constant, K e of the motor b.) and takes armature current of 50 A. Open windings 2. Ques 9. Ignore its friction, windage, and core losses for the purposes of this problem.

DC MOTORS DC motor operates on the principle that when a current carrying is placed in a magnetic field, it experiences a mechanical force given by F = BIL newton. 12. The speed and torque produced in a DC motor depends on a variety of factors. A DC motor is defined as a class of electrical motors that convert direct current electrical energy into mechanical energy. PDF Version. The resistances and inductances of the field and armature Therefore, force per conductor = f c = BLI a /A. State the three classifications of dc generators. SOLVED PROBLEMS ON DC MACHINE MAGNETIC CIRCUIT Example.1 Calculate the ampere-turns turns for the air gap of a dc machine given the following data. To reduce the Harmonic in generated EMF. Field SystemField System: the part of the motor: the part of the motor that provides the magnetic flux. when T d =0) or

With a in BLDC motor, it is achieved using multiple feedback sensors. The underlying principles for the working of a BLDC motor are the same as for a brushed DC motor; i.e., internal shaft position feedback. ELEN 20013 Basic EE Lecture 09 DC Generators and Motors Solution to Sample Problems DC Generator Equivalent Circuit: Sample Problems 1 1. Chapter 13 - AC Motors. A separately excited DC motor has an armature resistance of 0.5 ohms (Ra = 0.5 ). Most electric motors operate through the interaction of magnetic field and current carrying conductors to generate force. Solved Problem. The converter produces 3. Define stalling current of DC motor. [4] A 230V,960b) rpm and 200 amp separately excited dc motor circuit, find the motor output, the armature current, external resistance to be inserted in the armature circuit and overall efficiency. Application to Control DC Motor Operation in 4 Quadrants. Turn-to-turn short If the motor keeps running with stator faults, a high current will flow through the windings where the problem is located. - Swap any two of the three motor leads to reverse motor rotation. Translate PDF. Therefore, for a given DC generator, the induced EMF in the armature is directly proportional to the flux per pole and speed of rotation. Derive the transfer fb) unction of an armature controlled dc motor and draw the closed loop block diagram. 1. B. the armature current will reduce. ANS. Fig. Armature: the part of the motor which carries current that interacts with the magnetic flux to produce Figure 1: DC motor block diagram. The field windings make up the stator, which is the static element of the motor. This eBook of Basic electrical engineering is in PDF format which is easily downloadable. Use shunt motor equations and circuit model to compute 14. 2. 15 Problem 26 A 200V d.c. motor develops a shaft torque of 15 Nm at 1200 rev/min.

To begin with, few problems on d.c motors have been solved and then problems on the generator are taken up.

What do these rating means? Turn-to-turn short If the motor keeps running with stator faults, a high current will flow through the windings where the problem is located. R 1 = V 1 I, R 2 = V 2 I, R 3 = V 3 I. R 1 = 5.0 1.0 = 5.0 R 2 = 8.0 1.0 = 8.0 R 3 = 7.0 1.0 = 7.0 . ANS. For a beginner, it is suggested to follow the following guidelines for successful completion of the problem. DC MotorsDC Motors Terminology Rotor: the rotating part of the motor: the rotating part of the motor. Find N 2? Read the problem and note The voltages applied to the field and armature sides of the motor are represented byV f and V a. ( 1) It is clear from eqn.

Where. DC Circuits Resistance Review Following the potential around a circuit Multiloop Circuits RC Circuits Homework for tomorrow: Chapter 27 Questions 1, 3, 5 Chapter 27 Problems 7, 19, 49 WileyPlus assignment: Chapters 26, 27 Homework for today: Read Chapters 26, 27 Chapter 26 Questions 1, 3, 10 Chapter 26 Problems 1, 17, 35, 77 Volume 3 of 4 Module 7 - Basic AC Theory Case 1 For Lap winding, number of parallel paths A = P. 3. 11. 12. by Alexsander San Lohat. (a) Sketch the load voltage v o and find its total harmonic distortion (THD). Since the question here is to find the current through AB, 6 resistor is considered as the load. EO 1.1 Using the right-hand rule for motors, DETERMINE the direction of the magnetic field, direction of current flow, or force on a conductor. Sparking at brushes in a dc motor may be due to. From an ammeter reading, the line current to the motor is 102 A. An external magnetic field is going through the loop of the circuit up out of the page indicated by the 0 in the plane of the loop. 2. D.C Motor For a beginner, it is suggested to follow the following guidelines for successful completion of the problem. Amplitudes of the triangular wave (carrier) and sine wave (modulating) are compared to obtain PWM waveform. Dc Motors, Generators and Energy Conversion Devices Lesson 13 332a.pptx 1 Lesson 13 332a.pptx 2 Explain how changing field excitation of a shunt motor affects its performance Explain how the internal feedback inherent in the shunt motor maintains a nearly constant shaft speed. WHAT IS ELECTRIC MOTORS? This is very important for brush conductivity on the commutator and the current density so the brushes can maintain a certain lubricity when contacting the commutator under load. This equation is called the dc motor speed equation and is just a straight line with a negative slope. X5.15 A shunt dc motor is fed from a 250 V dc bus. 2. A 480-V, 60 Hz, 400-hp 0.8-PF-leading eight-pole -connected synchronous motor has a synchronous reactance of 0.6 and negligible armature resistance. Fig.

1. What is the value of current I4 (in A) for the given junction? Let us take a look at some problem. troubles in commutator. 2. For starting a D.C. motor a starter is required because. This unit will discuss how these magnetic fields are produced in dc motors, and how magnetic fields induce voltage in dc generators.

Other members of the family are the direct-current (dc) motor or generator, the induction motor or generator, and a number of derivatives of all these three. Motor has been running, then fails to start. EO 1.2 STATE the function of torque in a direct current motor and how it is arrangement is required to get the dc power to its field windings. Shut down the main supply. then: T d =T load. C.03 Identify available solutions and their impact including evaluating credibility of information, and locating information. Explain the effect of motor reaction in a dc generator. (a) To find Nortons current, Remove the load resistor (6 ), short it with a wire and the circuit is redrawn as below.

To establish the torque equation, let us first consider the basic circuit diagram of a dc motor, and 3/7/2011 13 Losses and Efficiency of a DC Motor The efficiency of a d.c. motor is the ratio of Questions on Electric Motors with answers-. hence: P T T KI EI OUT load d= = = = a a a. and . Plot the torque-speed curve of each of the three motors. (d) the speed will reduce. EXPERIMENT No. 6 TORQUE-SPEED CHARACTERISTICS OF DC MOTORS Use a variable DC supply to determine the armature resistance, series winding resistance, field winding resistance, maximum and minimum values of the field rheostat. Note that the rated current of the field winding and rheostat is 0.5A, while that of the series and armature windings is 3A. Explain the causes of armature losses. A shunt generator delivers 450 A at 230 V and the resistance of the shunt field and armature are 50 and 0.03 respectively. The 3-phase set of currents, each of equal magnitude and with a phase Its digital version, known as REGULAR sampling is widely used in industry. After the introduction of the DC electrical distribution system by Edison in the United States, a gradual transition to the more economical AC system commenced. If the efficiency is 80%. DC Motor Transfer Functions (Reference: Dorf and Bishop, Modern Control Systems, 9th Ed., Prentice-Hall, Inc. 2001) The figure at the right represents a DC motor attached to an inertial load. Basically an analogue method. We can consider a DC motor in terms of the input-output relationship. What is common to all the members of this fam- neering analysis is that it greatly simplies the calculations required to solve circuit problems. DC motors must be applied with the proper amount of load. Where : n o = no load speed (i.e. Show Explanation. 1.The phase sequence or rotation of the machine must be the same as that of the system. 5 DC Generator Problems with Solution Part 1. An external inrush current limiter circuit can be added to a dc/dc converter to mitigate the effects of peak currents. Carbon Brushes.

troubles in brushes. Using the Ohm's Law, we can find the resistances of the first, second and third resistors. Now, using the equivalent resistance, we can find the resistance in the fourth resistor. Q.27-3 1. OUT (100%) (100%) (100%)a a a IN DC a DC P EI E P VI V === This high Which of the following statement is TRUE? The fine lines occur when copper is transferred from the commutator to the brushes. This high The motor is operating at 1200 rpm supplying 30 HP to a coupled mechanical load. Problem A 220 V dc shunt motor runs at 500 rpm when the armature current is 50 A. (a) Sketch the load voltage v o and find its total harmonic distortion (THD). 16. QUESTIONS: 1. The theoretical approach to the efficiency of a DC motor is similar to the DC generator method. (c) WHAT IS ELECTRIC MOTORS? Solution: The efficiency of a motor = 100 % The output power of a motor is the power available to do work at - Do not reverse the leads from the battery to the ESC under any circumstances. I a = 50. A dizzying array of parameters specify a motor The two motors you have are small direct-drive, Contact Us. NPTEL Administrator, IC & SR, 3rd floor. In D.C. shunt motors as load is reduced. assume that mechanical losses can be ignored, the efficiency of a DC motor can be expressed simply as the ratio of back EMF to applied voltage because: T d =T load +T mech loss. 1. 1. The rotor will constantly be turning to align its magnetic field with that of the stator field. Motor damaged and the fan guard is contacting the cooling fan.

(c) the speed will remain almost/constant. Synchronous motors have the following characteristics: A three-phase stator similar to that of an induction motor. Module 6 - DC Motors This module describes the types of DC motors and includes discussions of speed control, applications, and load characteristics. Solved Problems: Electrical Engineering and Instrumentation

The time taken by the motor to come to rest depends upon the kinetic energy stored in the rotating system. 11 Lesson 11 332a.pptx A. current in the conductor aovtaat of conductor. step, record the DC source current and motor speed. Under rated load conditions, the machine draws 60 A of armature current (ia), runs at 1000 RPM (wm), and the induced back-EMF voltage is 200V (ea). The three stator coils of a three phase alternator are positioned apart by how many electrical degrees? They include: 1. IIT Madras, Chennai - 600036. Speed and Direction of Rotation . E b1 = V-I a1 R a = 250-(50x0.25) = 237.5V This speed control system is an electro-mechanical control system. Tel : (044) 2257 5905, (044) 2257 5908, 9363218521 (Mon-Fri 9am-6pm) Email : support@nptel.iitm.ac.in. The basic idea of an electric motor is to generate two magnetic fields: rotor magnetic field and stator magnetic field and make the stator field rotating. 13. Fig. How to solve your DC motor problem at homeHi guys,Today,l am making 'How to solve your DC motor problem at home'. So, this form of motor does not start on heavy loads. The speed of this type of DC motor is determined by the following methods: Field control: Reduction of the field increases the speed of the device while improving the field causes reduction in the speed. Speed regulation of this type of motor can be obtained by controlling the field. 11. Current/conductor I c = I a A. Medium voltage stators are often used. D. none of the above. At starting; Eb = 0. Read the problem and note down the information provided about the motor. Known : Resistor 1 (R1) = 4 . Resistor 2 (R2) = 4 . Resistor 3 (R3) = 8 . (a) the speed will increase abruptly. Carbon Brushes. Control of DC motor operation in 4 quadrants can be achieved using a Microcontroller interfaced with 7 switches. EO 1.2 STATE the function of torque in a direct current motor and how it is Ques 10.

The speed and torque produced in a DC motor depends on a variety of factors. If the armature winding, after being disconnected from the source, is 14. 500 V terminal voltage serial excited DC motors armature and field resistance is 5 together. Yoke, Poles, Brushes, Bearings, Shaft, Commutator, Pole shoes, commutator poles and armature windings. troubles in armature. Improve Cooling. In D.C. shunt motors as load is reduced. (a) voltage control method. C. the motor will attain dangerously high speed 1. Given data . On a certain load it takes 20 A current from the DC supply and its speed is 1000 1/min. Ward-Leonard control is basically a. 2- In a series DC motor if the torque is reduced to its third, how much does A DC generator has a 100-kW, 250-V rating. Motor may have to be replaced. Shut down the main supply. Transformers: Construction and Principle of operation of single-phase transformer, EMF equation, Single-phase autotransformer. The

Determine the current through AB in the given circuit using Nortons theorem. Motor is damaged and the armature is rubbing against the magnets. An electric motor is an electrochemical device that converts electrical energy into mechanical energy. R > R 2 2. The rpm sensor dc 2 V dc 0 t 0 t 1 t 2 t 3 t 4 t 5 Triangulation method (Natural sampling). Where : n o = no load speed (i.e. Most dc/dc converters have an input filter stage with capacitors that charge at a slow rate. Record all nameplate information for the induction motor. Phase-to-phase 4. Solution. If the flux of the motor is reduced by 10% without changing the load torque, find the new speed of the motor. DC motors must be applied with the proper amount of load. -The single -phase full bridge inverter shown below is operated in the quasi square wave mode at the frequency f = 50 Hz with a phase-shift of = 2/3 between the half-bridge outputs v ao and v bo. Increase EMF. 13. 3. DC Motor: Back e.m.f., speed and torque of a DC Motor, Conditions for maximum Power. Electric voltage (V) = 40 Volt. It is known that and . They include: 1. Assume that EA is directly proportional to the field current IF (in other excessive load. The flux of this motor is generated by the armature current. Transcribed image text: DC Machines Practice Problems 1- A series motor has the current I. Common problems with commutators and brushes include threading, grooving, copper drag, and flashover.

V = 250. Replace fan guard. Most stator faults are caused by insulation breakdown which leads to winding failure. A three-point starter is suitable for. Met by research and preparation prior to group discussion. Chapter 5: Synchronous Motors 5-1. Phase-to-phase 4. chapter 09: synchronous motors. chapter 11: special machines.

Electrical Engineering : Dc Motors QUESTIONS AND ANSWERS :: part1 : 1 to 5. Example 11-3: A 50 HP, 240 Vdc separately excited motor is operating at 1000 rpm. I sh is the shunt field current; R sh is the shunt field resistance; Induced Back EMF: The armature induced voltage E b is proportional to the speed & it is given by:. b) Supply the dc power from a special dc power source mounted directly on the shaft of the synchronous generator. The relation among the main supply, back EMF & armature current can be expressed as Eb = V IaRa.