Electrical Machines Lab 1 Electrical Machine-l (D.C) Laboratory Manual, ELECTRICAL MACHINES -I [EL20323] LABORATORY MANUAL B.TECH III Sem EE Electrical Machine Lab – I [EL20323, Faculty Of Engineering And Quantity Surveying (FEQS) EEE 3209 Electrical Power And Machines Lab Report Experiment 1: DC Machines, LABORATORY MANUAL of ELECTRICAL MACHINES II. DC Shunt Motor Speed Control The speed characteristic of a shunt motor is different compared with a series motor. To derive the speed of a DC motor, we start with the equation for the DC motor’s EMF (Electromagnetic Force). Thus, the magnitude of Eb can be given by EMF equation of a DC generator.Eb = PØNZ/60A(where, P = no. That means speed control of dc shunt motor is simple, easy and economical. This method is not suitable for intermittent loads. Speed Control of DC Shunt Motor : In a shunt connected dc motor, the speed is approximately proportional to the input voltage to the armature and inversely proportional to the current in the field winding. You can download the paper by clicking the button above. • If these values are plotted, the graph representing the variation of speed with torque developed is obtained. Similarly, self-excited motors classified into three types namely DC series motor, DC shunt motor, and DC compound motor. So the current through the armature is decreased and speed of the motor is self-regulated. Field is directly connected across the supply so flux is not changed due to variation of series resistance. The speed equation of a DC motor shows that, N α E b / φ or N α (V – I a R a)/ φ But the resistance of armature winding is small. This armature control method is based on the fact that by varying the voltage across the required voltage. An increase in controlling resistances reduces the field current with a reduction in flux and an increase in speed. In dc shunt motor, when supply voltage V is kept constant the shunt field current and hence flux per pole will also be constant. Enter your email below to receive FREE informative articles on Electrical & Electronics Engineering, SCADA System: What is it? Often we want to control the speed of a DC motor on demand. This method is only applicable when we want speed which is higher than the normal speed of the motor. of poles, Ø = flux/pole, N = speed in rpm, Z = no. The speed relation of Dc shunt type motor is given as N α (V – Ia. Speed control methods for a DC series motor can be classified as: Speed adjustment of a DC series motor by armature control may be done by: This is the most common method employed. Flux Control Method : It is seen from the above equation that N α 1 / φ. Speed vs. load for a DC shunt motor. Armature Voltage Control of DC Motor In armature voltage control method the speed control is achieved by varying the applied voltage in the armature winding of the motor. Theory Vo la R, The speed of a DC motor is given by N= K, ape tpm. Field Rheostat Controlled DC Shunt Motor In this method, speed variation is accomplished by means of a variable resistance inserted in series with the shunt field. B. load. Therefore speed of the 3 types of DC motors – shunt, series and compound – can be controlled by changing the quantities on the right-hand side of the equation above. SPEED CONTROL OF DC SHUNT MOTOR DATE: AIM: To control the speed of DC shunt motor by Armature control method and Field control method APPARATUS REQUIRRED: S. No. A DC motor's speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings. DC Starter face plate type suitable for above motor. Note the wire link acting as a current shunt, circled in red. Here speed control is obtained over wide range but below normal speed. By dinesh | August 16, 2020. Lesser the diverter resistance less is the field current, less flux therefore more speed. The resistance can be increased in the shunt winding and armature branch by … This method of speed control is independent of load on the motor. This method of speed control is also used in DC compound motor. This is another method of increasing the speed by reducing the flux and it is done by lowering number of turns of field winding through which current flows. Objectives: To obtain the speed characteristics of a D.C shunt motor as a function of (i) armature voltage and (ii) field current. Speed Vs Torque characteristics of DC Shunt motor • From the above two characteristics of dc shunt motor, the torque developed and speed at various armature currents of dc shunt motor may be noted. By this method a DC Shunt motor’s speed is controlled through a field rheostat. Speed Control of D.C. Motors. This method gives speed above normal and the method is used in electric drives in which speed should rise sharply as soon as load is decreased. Speed of a DC motor Back emf E b of a DC motor is nothing but the induced emf in armature conductors due to rotation of the armature in magnetic field. This intentional change of drive speed is known as speed control of a DC motor. Applied voltage ( voltage control method ). This method of speed control is independent of load on the motor. The exciting current can be varied by varying the armature shunting resistance R2. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. Static Ward Leonard drives are being used these days because of the drawbacks of the classical method. These two methods are: Armature controlled DC shunt motor can be performed in two ways: In armature resistance control a variable resistance is added to the armature circuit. Here the controlling resistance is connected directly in series with the supply of the motor as shown in the fig. of … Applications of DC Shunt Motor. To study the methods of controlling the speed of shunt DC motor. This method of speed control needs a variable source of voltage separated from the source supplying the field current. E b = PNZ /60A = V– I a R a . Therefore speed control of DC motor can be classified into: We will discuss how both of these methods control the speed of DC series motors and DC shunt motors. The speed relation of Dc shunt type motor is given as N α ( V – Ia . The different methods of speed control of DC shunt motor are Flux Control Method, Armature Control Method and Voltage Control Method. In this method, speed variation is accomplished by means of a variable resistance inserted in series with the shunt field. By varying the current supplied to the stator As the voltage around the rotor and stator is the same, the speed of the motor can be controlled by controlling the current through the stator or rotor. Before discussing the applications of series motors, let us recall the typical features of a dc series motor. Shunt-wound DC motor or DC shunt motor is a self-excited DC motor that operates on direct current, and the field winding connects in parallel to the armature winding. 5. The relationship given below gives the speed of a D.C. motor. The converters used are choppers (in case of DC supply) or controlled rectifiers (in case of AC supply). Therefore the voltage drops I a R a will be negligible as compared to the external supply voltage V. . Ra ) When the armature current is increased the speed … Since the input voltage is constant, the flux generated is also constant. Motor Control Basics: Drive Operating Modes. The speed characteristic of a shunt motor is different compared with a series motor. Neglecting the losses and saturation, the speed of ... GATE EE 1999 The speed equation of a DC motor shows that, N α E b / φ or N α (V – I a R a)/ φ But the resistance of armature winding is small. The power loss in the control resistance of DC series motor can be neglected because this control method is utilized for a large portion of time for reducing the speed under light load condition. DC shunt motors are used in Machine tools such as lathes where constant speed is required. Although a far greater percentage of electric motors in service are ac motors, the dc motor is of considerable industrial importance. 1.) This method of speed control is employed for DC series motor driving cranes, hoists, trains etc. This method is best suited for steel rolling mills, paper machines, elevators, mine hoists, etc. A. field excitation. SPEED CONTROL OF DC SHUNT MOTOR DATE: AIM: To control the speed of DC shunt motor by Armature control method and Field control method APPARATUS REQUIRRED: S. No. The speed is maximum at minimum value of flux, which is governed by the demagnetizing effect of armature reaction on the field. Theory: We know that back e.m.f is produced by the generator action of the motor.. E b = PØNZ / 60A (where, P = no. DC Shunt Motor Speed Control. From the expression of the speed of a DC motor, we have seen that the speed is directly proportional to the difference between supply voltage and its armature resistance drop. Before discussing the speed control of dc shunt motor, we have to find the factors affecting the speed of a DC motor. (b) … In the shunt motor, speed can be controlled by conjunctive a variable resistor Rc in series with the shunt field winding. DC Motor Speed Control in Series Types. The most commonly used method of speed control of a dc motor is by varying. This is different to speed regulation – where the speed is trying to be maintained (or ‘regulated’) against the natural change in speed due to a change in the load on the shaft. The back emf equation for dc motor is. THEORY The back emf for a DC motor is given by, P NZ Back emf, E b = 60 A The number of poles, P the armature conductors, Z and the number of parallel paths, A are constant for a particular machine. speed is low at high torque and vice versa. When supply voltage (V) and armature resistance Ra are kept constant, the Speed is directly proportional to armature current (Ia). A. voltage applied to the motor . By varying the current supplied to the rotor 2. The characteristic show that dc shunt motor speed remains almost constant from no-load ( I a ≃ 0) to full load ( I a =rated value) and that is why dc shunt motor is used in applications where speed is required to remain almost constant throughout the operation e.g Lathes, spinning and weaving machines, drills etc. As a DC Shunt motor attains its complete speed, then the armature current can be directly connected to the motor load. The combination of a rheostat shunting the armature and a rheostat in series with the armature is involved in this method of speed control. Speed Control of DC Shunt Motor There are three method which are famous for motor speed control i.e. Theory : We know that back e.m.f ( ) is produced by the generator action of the motor. D. none of these. Control of motor torque and velocity or speed are operating mode selections available to most basic DC drives and to some flux vector type AC drives. One can control the speed of a DC shunt motor in two ways: 1. A brushed DC electric motor is an internally commutated electric motor designed to be run from a direct current power source. This paper describes the speed control of a DC shunt motor using conventional controllers (PID, IMC) and Fuzzy Logic controller based on Matlab Simulation program. Such a fine speed control is generally not possible with ac motors. This method is used in printing press, cranes, hoists where speeds lower than rated is used for a short period only. Starting of DC Motors A starter is a device to start and accelerate a motor. View Answer: Answer: Option B. If we add resistance in series with the armature, the armature current (Ia) decreases and hence speed decreases. Types of DC Motors • Separately Excited Motor • Shunt Excited Motor • Series Excited Motor • Compound Excited Motor • Permanent Magnet (PM) Motor. The DC shunt motor torque … The universal motor can operate on direct current but is a lightweight brushed motor used for portable power tools and appliances. Knowledge of schematics is recommended as well as review of the lessons, Introduction to DC Motor Theory and Series, Shunt, and Compound DC Motors. This method avoids disadvantages of poor speed regulation and low efficiency of armature-resistance control methods. In this method a number of tapping from field winding are brought outside. The starting torque for this motor is about 1.5 times the full-load torque (Figure 7-49). Speed Control of DC motor by varying armature and field resistance; Speed control of DC motor by using Ward- Leonard Method of speed control; Load Characteristics of DC shunt generator As a DC Shunt motor attains its complete speed, then the armature current can be directly connected to the motor load. Speed Control of DC Motor: Armature Resistance Control and Field Flux Control The dc motor converts mechanical power into dc electrical power. The relationship given below gives the speed of a D.C. motor. This method is employed in electric traction. This paper describes the speed control of a DC shunt motor using conventional controllers (PID, IMC) and Fuzzy Logic controller based on Matlab Simulation program. Here the field flux can be reduced by shunting a portion of motor current around the series field. Where K = 60A/ ZP and it is constant. Academia.edu no longer supports Internet Explorer. Thus by varying the pulse-width, we can vary the average voltage across a DC motor and hence its speed. If you are a student of Electrical Engineering then you should know that "Speed Control of DC Shunt Motor".Of course, before going to know Speed control of DC Shunt Motor we will learn what is DC Shunt Motor. As the armature rotates in a magnetic field, it induces electricity. Hence the speed can be varied by changing: Terminal voltage and external resistance involve a change that affects the armature circuit, while flux involves a change in the magnetic field. Speed Control Methods of DC Motor – Voltage, Rheostatic & Flux Control of Series & Shunt DC Motors A DC motor is used to convert the direct current (DC) electrical power into mechanical power based on the forces produced by magnetic filed (s). This article discusses an overview of the series motor, and the main function of this motor is to convert electrical energy to mechanical energy. This is sufficient to start this type of motor while under full load. The running speed of a dc series motor is basically determined by. Both windings are exposed to the same power supply voltage, and this motor can maintain a constant speed with any load. Equivalent Circuit of a DC Machine (separately excited) E A =kΦω τ ind =kΦI A. Small DC motors are used in tools, toys, and appliances. DC machine Motors and generators are dc machines. The basic adjustable armature voltage control method of speed d control is accomplished by means of an adjustable voltage generator is called Ward Leonard System. The speed of dc series motor prominently drops when we increase the mechanical load of the motor. Thus, the magnitude of E b can be given by EMF equation of a DC generator. C. armature resistance. of armature conductors, A = parallel paths) E b can also be given as, In shunt motor, flux produced by field winding is proportional to the field current Ish. When the load is extremely low within a shunt motor, then the armature current can also be low. There are so many methods for controlling the speed of a DC shunt motor but field rheostat control method is most reliable, economic and independent of load on the motor. Flux Control Method : It is seen from the above equation that N α 1 / φ. A shunt DC motor has a feedback mechanism that controls its speed. The shunt DC motor is a constant speed motor. This speed control method is also known as Ward Leonard Method, which is discussed in detail under the topic Ward Leonard Method or Armature Voltage Control. The different methods of speed control of DC shunt motor are Flux Control Method, Armature Control Method and Voltage Control Method. A DC motor is used to convert the direct current (DC) electrical power into mechanical power based on the forces produced by magnetic filed(s). We know that the EMF equation of DC motor is equal to: Hence with E = V – IaRa, we derive the speed of the DC motor (N): Electrical4U is dedicated to the teaching and sharing of all things related to electrical and electronics engineering. i.e., φ α Ish. This EMF is generated in a reverse direction, thus limiting the armature current. Fig 2: DC Motor speed control … To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. Speed of a DC motor Back emf E b of a DC motor is nothing but the induced emf in armature conductors due to rotation of the armature in magnetic field. Therefore the voltage drops I a R a will be negligible as compared to the external supply voltage V. . Industrial Use : Lathes, Drills, Boring Mills, Shapers , Spinning, and weaving machines Series Motor: It is a variable speed motor i.e. 3. Such type of control is impossible in an AC motor. This is applied for DC shunt motor. Voltage Control Method of Speed Control of Shunt DC Motor In this method, we apply the variable input voltage to the motor to control its speed. C. effective number of conductors in series. Speed Control of DC shunt motor 1.Field control methods Weakening of field causes increase in the speed of a motor and strengthening of field reduces the speed.Speed adjustment can be obtained by: Field-rheostat control involving the variation of flux by means of a field rheostat. The classification of speed control methods for a DC shunt motor are similar to those of a DC series motor. Rotating M-G sets are replaced by solid state converters to control DC motor speed. The principal advantage of a dc motor is that its speed can be changed over a wide range by a variety of simple methods. This method of speed control is not economical due to considerable power losses in speed controlling resistances. The combination of a shunt motor torque … the most important subject in electrical Engineering varies by varying current... Theory Library values are plotted, the speed of a D.C. motor connected directly in series with supply... 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Of control is generally not possible with AC motors variety of simple methods affecting the speed characteristic a. 'Ll email you a reset link is an approximately constant speed with torque developed is obtained losses in speed of. An AC motor back EMF ( Eb ) and speed of a DC series motor can be changed a... / 60A ( where, P = no a lightweight brushed motor for... A rheostat shunting the armature current below resistor, variable resistor Rc is called the shunt field shunting. The normal speed of the motor called the shunt field here the controlling is!: ( a ) speed control methods and DC compound motor intentional change of drive speed is maximum minimum. Is given as N α ( V – Ia b can be given by EMF equation of a shunt are. Is accomplished by means of an automatic control device therefore, DC shunt motor speed control of. Control: to control DC motors a Starter is a device to start the motor back EMF ( Eb and... 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