Often we want to control the speed of a DC motor on demand. This intentional change of drive speed is known as speed control of a DC motor. Speed control of a DC motor is either done manually by the operator or by means of an automatic control device Self-Speed Regulation of a Shunt Wound DC Motor A very important and interesting fact about the DC shunt motor, is in its ability to self-regulate its speed on the application of the load to the shaft of the rotor terminals
Speed Control of DC Shunt Motor by SCR The figure shows an SCR circuit that can be used for the speed control of dc shunt motor. In this circuit, the supply voltage to the armature can be varied by varying the conduction angle of the SCR, so the smooth variation in speed is possible. Here the diac is used to trigger the SCR Speed Control of Shunt DC Motors There are 2 most common methods used for speed control of the shunt motor. Field resistance RF adjustment. The terminal voltage applied to armature adjustment 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 Speed Control of DC Shunt Motor with Field and Armature Rheostat Control 79 2. Circuit Diagram: 3. Working Principle From the above circuit diagram, we can conclude that if we want to increase the speed of the shunt motor, we will vary the field resistance. As resistance increased, the value of the field current will reduce Therefore, the motor must be separately excited to use armature voltage control., if applied voltage is constant 2-Field Control:, if applied voltage is constant The speed is inversely proportional..
To study the speed control of a DC shunt motor by the following methods: Armature voltage control: Variations of speed with armature voltage control at constant field current. Field Control: Variation of speed with variation of field current at constant voltage. Theory: Fundamental Relationship Aim To study the speed control of D.C. Shunt motor by armature control method. Draw the graph between armature voltage and motor speed by varring the armature voltage
Armature Resistance Control Method for DC Shunt Motor With this method, the speed of the DC motor can be controlled by controlling the armature resistance to control the voltage drop across the armature. This method also uses a variable resistor in series with the armature The armature of the shunt motor M (whose speed is to be controlled) is connected directly to a d.c. generator G driven by a constant-speed a.c. motor A. The field of the shunt motor is supplied from a constant-voltage exciter E. The field of the generator G is also supplied from the exciter E A shunt DC motor has a feedback mechanism that controls its speed. As the armature rotates in a magnetic field, it induces electricity. This EMF is generated in a reverse direction, thus limiting the armature current. So the current through the armature is decreased and speed of the motor is self-regulated Objectives: To obtain the speed characteristics of a D.C shunt motor as a function of (i) armature voltage and (ii) field current. Apparatus: Theory: Any D.C. motor can be made to have smooth and effective control of speed over a wide range. Th In the shunt motor, speed can be controlled by conjunctive a variable resistor Rc in series with the shunt field winding. In the diagram below resistor, variable resistor Rc is called the shunt field regulator. Fig: (a) Speed control of a D.C. shunt motor by variation of field flux. (b) The diverter in parallel with the series of D.C. Motor
CONSTRUCTION OF SHUNT DC MOTOR. The field winding of DC shunt motor is wound with many turns to increase the flux linkage and the armature winding is designed to carry higher current. This is done because the torque is proportional to the armature current and the flux. DC shunt motor is self-excited type motor because the field and armature winding are energized with the same DC supply The brushed DC electric motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary magnets (permanent or electromagnets), and rotating electromagnets.. Advantages of a brushed DC motor include low initial cost, high reliability, and simple control of motor speed. Disadvantages are high maintenance and low life-span for high intensity uses
The speed control applications of a DC motor varies depending on how the motor is used, and how its mechanical power is utilized. It is mainly the motor applications how the speed control will be utilized and /or applied A robotic application is.. SPEED CONTROL OF DC MOTOR (SHUNT TYPE) AIM (a) To study the speed control of DC motor below the normal range by armature resistance control and to plot speed Vs armature voltage, characteristic. (b) To study the speed control of DC motor above the normal range by field control and THEORY The back emf for a DC motor is given by, P NZ Back.
Speed Control Methods of a DC Motor Speed of a DC motor can be varied by varying flux, armature resistance or applied voltage. Different speed control methods for different DC shunt and series methods are there. Speed Control of Shunt Motors It's called speed regulation of a DC motor, which is the capability a DC motor shows to recover the speed under variable load. In general the speed of a shunt DC motor is directly proportional to the armature voltage and inversely proportional with the field current, disregarding inherent losses
The same theory works with DC motor i.e when the load is applied to the dc motor its speed decrease, but it is not desirable since in many application such as conveyors, lathe machine etc. we need constant speed motor. DC shunt motor. The speed regulation of DC shunt motor is between 10 -15 %. shunt motor speed characteristic DC Shunt motor DC 5-HP, 1500 rpm, 16.7 amp, 220 V 1 2. Tachometer Digital (0-10000) r. p. m. 1 3. Voltmeter MC (0-300) volts 1 4. Ammeter MC (0-1/2) A(0-5/10) A 1 each 5. Rehostat Single Tube 260Ω, 1.2 A 1 6. Rehostat Single Tube (0-2000) rpm 1 THEORY: DC Motor: A machine that converts DC electrical power into mechanical power is known as DC. The motor speed is controlled by a full wave bridge rectifier. The firing angle α is set at 60°, and the average speed is 1250 rpm. The applied a.c. voltage to the bridge is 230 V at 50 Hz
SPEED CONTROL OF DC SHUNT MOTOR 9 BRAKE TEST ON DC COMPOUND MOTOR 10 BRAKE TEST ON DC SHUNT MOTOR 11 Speed : APPARATUS REQUIRED: THEORY: The magnetization or Open Circuit Characteristic of a self-excited DC machine shows the relation between the No-load generated e.m.f (E Lab 7: DC motors: shunt, series, and compounded. Objective: to study the torque vs. speed characteristics of DC motors; to calculate the efficiency of these motor types. Equipment: Power Supply, DAI, Direct current machine (DC motor) (8211), Electrodynamometer (8960), timing belt. Theory: Electrodynamometer measures torque. Electrodynamometer. 4 Load test on dc shunt motor 14 5 Speed control of dc shunt motor by armature and field control. 18 6 Swinburne's Test on dc motor. 22 Second Cycle Experiments Exp. No. Title of the Experiment Page No 7 Retardation test on dc shunt motor. 26 8 Field Test on dc series machines. 30 9 Regenerative test on dc shunt machines. 3
. load, the horsepower increases and decreases ___. in direct proportion to the speed. The primary method of varying the speed on a DC shunt motor is to adjust the voltage and current on the field winding or. 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. Apparatus Type Range Quantity 1 Voltmeter MC (0-300)V 1 2 Ammeter MC (0-20)A 1 3 Rheostat 1250Ω/0.8A, 50Ω/3.5A 2 4 Tachometer Digital 60000RPM 1 FUSE RATING: 40% of rated current. As speed is inversely proportional to the flux. The flux is dependent on the current through the shunt field winding. Thus flux can be controlled by adding a rheostat (variable resistance in series with the shunt field winding as shown in above figure. At the beginning the rheostat is kept at minimum Motor Control Basics: Drive Operating Modes. 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. With some products, Velocity mode operation can include capacity for regeneration. 1.) DC Drives - Torque Control: To control DC motors torque, a DC drive will regulate armature current The speed torque characteristics of a dc shunt motor with armature resistance control. A comparison of speed adjustment of a dc shunt motor by means of field control and be means of general use. In field control the adjustment can be obtained by means of a small rheostat and relatively good speed rgu1ation is obtained for all speeds
speed. Hence DC shunt motors are typically used applications that require five or more horse power . Mathematical Modeling of DC SHUNT Motor DC shunt motors have the field coil in parallel (shunt) with the armature. The current in the field coil and the armature are independent of one another. Dc shunt motor data is show in the table 1 In a DC shunt motor (the field is in parallel with the armature), the speed is controlled by increasing or decreasing the applied voltage to the shunt field or armature by means of a field rheostat or an armature rheostat Variable Speed Drives Motor Speed Control • DC Shunt Motor Speed Controls • Decreasing field voltage, by increasing field resistance, will also decrease field current • Weaker magnetic field on the field poles • Lessens motor torque-producing ability • Current in the armature conductors • Strength of the magnetic field • Most likely not be able to produce the required torque to move the load at the higher speed In the shunt motor, speed can be controlled by connecting a variable resistor R c in series with the shunt field winding. In the diagram below resistor, R c is called the shunt field regulator. Figure: (a) Speed control of a D.C. shunt motor by variation of field flux. (b) The diverter in parallel with the series of D.C. Motor
In Fig. 1.17, four important characteristics of a dc shunt motor, namely, torque, speed, armature current, and efficiency, each plotted against the useful output power, are shown. These curves are also known as performance curves of a motor. From the speed-useful output power curve it is seen that the shunt motor has a definite speed at no load PROCEDURE: (FIELD CONTROL METHOD) 1.Connect the circuit as shown in fig. 2.Start the motor by using 3-point starter. 3.By slowly varying the field rheostat,run the motor to the rated speed and note the values of speed and field current. 4.Slowly increase the field rheostat and note the field current I f and speedN. 5.Draw the graph for N and I f Figure: Equivalent circuit for field control of DC motor Speed control by varying field current: In this method field circuit resistance is varied to control the speed of a d.c shunt motor. Let us rewrite the basic equation to understand the method. N = (V-IaRa)/kФ . If we vary I f, flux φ will change, hence speed will vary
Speed control of DC shunt motor (Armature, Field control) 4. Load test on single phase transformer 5. O.C & S.C Test on a single phase transformer 6. Regulation of an alternator by EMF & MMF methods. 7. V curves and inverted V curves of synchronous Motor 8. Load test on three phase squirrel cage Induction. A-Shunt wound motor is connected in parallel. B-Series wound motor. C-Separately excited field motor. Construct a trial motor, Figure 11. Connect the motor first in series, then in parallel as a shunt motor. Compare the speed and power of the two motors. Figure 11. Examine the trial motor with series and parallel connections. A Practical. . The DC shunt motor is well suitable for lathes, machine tools, driving, shafting, milling machine, conveyors etc. ( 3 ) Speed - torque ( N - T a This types of DC motors combines the feature of series and shunt motor and is used to get high starting torque and good speed regulation. Separately excited motor. This motor is considered to be a special case of shunt motor and has separate control over armature and field currents. The graph shows the torque speed characteristics of the types. Applications of DC Motor Shunt Motor: The characteristics of a shunt motor reveal that it is an approximately constant speed motor. Industrial Use : Lathes, Drills, Boring Mills, Shapers , Spinning, and weaving machines Series Motor: It is a variable speed motor i.e. speed is low at high torque and vice versa. This motor i
Hence, a DC shunt motor is able to self-regulate its speed, and can be referred to as a constant speed motor. When a load is applied to a DC shunt motor, its speed decreases, but the motor is able to self-regulate and quickly compensate for the lost speed. Image credit: electrical4u.com Uses for DC shunt motors. Because of their self-regulating. Field Weakening Method for Speed Control of DC Shunt Motor: The connection diagram for the speed control of DC Shunt Motor by varying the Field Flux is given below. As clear from the figure, a variable series resistance is added in the Field Circuit of DC Shunt Motor Starting of D.C. Motors A starter is a device that initiates and accelerates the motor. A controller is a device to start, control speed, reverse, stop and protect the motor. The motor's armature current is given b A dc motor is shunt connected and has an armature resistance of 1 2Ω and a shunt field resistance of 300 Ω When the motor is connected to a 500 V power supply the motor' s speed is 1500 rpm and it draws 40 A of armature current You can assume the rotatio DC shunt wound motor can maintain a constant speed, regardless of the load on the motor. Typical applications for DC shunt motors include fans, compressors, lathes and grinders. In a shunt motor, current is proportional to torque, thus in-creased torque allows the motor to increase its speed and compensate for the slowdown due to loading
To study the torque vs. speed characteristic of a series wound DC motor and calculate its efficiency. DISCUSSION. The Series DC Motor behaves differently than the Shunt DC Motor. As demonstrated in the previous lab, the shunt winding produces an almost constant speed of operation (low speed regulation) Motor Speed Control Quiz Questions Motor Speed Control Quiz Questions Answers) Search for: Related Pages Motor Controls Basic Theory Quiz ; Earthing / Grounding Quiz Questions; Power Quality Quiz Questions; DC Machines Quiz Questions; Single Phase Motors Quiz Questions; Basic Electronics Quiz Questions
The torque from a permanent magnet brushed DC motor is limited by its stator field, which gives it good low end ( low speed ) torque and a limited high end ( high speed ) torque. The permanent magnet brushed DC motor responds very quickly to changes in voltage. This is due to its constant stator field, thus giving it good speed control.
. This course consists of 11 interactive, on-line lessons that address AC and DC motor theory. Objective Identify the components of an AC Motor and explain their function. Explain the basic principles. Explain how to control the speed of a DC motor. Explain how a tapped resistor works. Explain a DC drive's control system and how it works; Included Modules. Introduction to AC Components and Motors: This is the first lesson in the AC/DC Motor Theory Course. This lesson identifies the components of an AC motor and explains their functions Knowledge of schematics is recommended as well as review of the lessons, Introduction to DC Motor Theory and Series, Shunt, and Compound DC Motors. Description. This is the final lesson in the iKNOW™ AC/DC Motor Theory Library. This lesson trains participants in starters, rotation direction, speed control, and drive controls of DC motors. Question is ⇒ The use of armature divertor in the rheostatic method of speed control for a D.C. shunt motor makes the method, Options are ⇒ (A) less expensive, (B) less wasteful, (C) suitable for rapidly changing loads, (D) unsuitable for changing loads, (E) , Leave your comments or Download question paper Hopkinson's test on DC shunt machines. Predetermination of efficiency. 6. Fields test on DC series machines. Determination of efficiency. 7. Swinburne's test and speed control of DC shunt motor. Predetermination of efficiencies. 8. Brake test on DC compound motor. Determination of performance curves. 9. Load test on DC series generator
Speed Control of DC Shunt Motors Points : Speed Control of DC Shunt Motors, Field Control Method, Armature Resistance Control, Armature Voltage Control, Ward-Leonard Method of Speed Control, Ward Leonard Higher System, The speed of a dc shunt motor can be controlled by field control, armature resistance control or armature voltage control. 1 2_To Study the Speed Control of Dc Shunt Motor by Armature Control and Field Control Method - Free download as PDF File (.pdf), Text File (.txt) or read online for free. To study the speed control of dc shunt motor by armature control and field control metho . FIGURE 12-16 Diagram of a shunt motor connected to a reversing motor starter. Notice that the shunt field is connected across the armature and it is not reversed when the armature is reversed. The direction of rotation of a DC shunt motor can be reversed by changing the polarity of either the.
The electric motor operation is based on the following points: • At least one of the two magnetic field is generated by a solenoid carrying a current. • Phase relation between the rotor and stator magnetic field (i.e. the load angle) must be always greater than 0° in order to keep the motor in motion (negative angles reverse th Likewise, the shunt field must be limited to the motor's nameplate value. Basic Operation. A DC drive supplies voltage to the motor to operate at a desired speed. The motor draws current from this power source in proportion to the torque (load) applied to the motor shaft. 100% Speed, 0% Loa In order for a DC motor to run, current mu st flow in the armature winding and the stator must develop a magnetic field (flux) , either by means of a shunt winding or a series winding (or both). The torque developed by a DC motor is directly proportional to the armature current and the stator flux. On the other hand, motor speed increases when th A series motor may reach a speed that is too high if it is started without a load. A shunt or separately excited motor can reach an excessive speed if the field becomes disconnected or reduced to a current that is too low. There may be some difficulty that makes a DC motor undesirable for use with centrifugal pumps or fans Shunt motors can have excellent speed regulation, even with varying loads. However, they usually lack the high starting torque of series motors. A motor and speed control circuit installed in a mini drill. Image used courtesy of Dilshan R. Jayakody . DC Motor Speed Control