To conduct load test on dc shunt motor and to find efficiency. This method is an indirect method of testing a dc machine. A belt and brake drum arrangement as shown in the circuit diagram can. Jun 25, 2015 electrical machines 1 viva questions and answers in this post we had collected some of the most frequently asked electrical machines 1 viva questions with detailed answers. We believe that these faqs will be useful for your practical exams and interviews as well. Using belt tightening hand wheels h1 and h2, the load of motor is adjusted to its rated value. The dc shunt motor is 120vdc with rated speed of 1800 revolutions per minute. 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. Study of load characteristic of dc shunt motor study of speed control of dc shunt motor using armature voltage control and flux field control method study and determine the losses of dc machine and correspondingly calculate the efficiency of dc machine by swinburns test method dc series wound motor study of operational working. Voltage can be applied to the terminals of the dc motor or external resistance can be applied in the armature. Dc shunt motor theory quiz questions electrician practice tests. Some drawbacks are that shunt wound brushed dc motors are more expensive than. Once the motor reaches its full speed, it remains constant.
In this article we are going to discuss about brake test on d. Dc motors plays an important role in energy conversion process. The servo brake and drive system motor test bench may only be placed into service with an additional. If the dc line voltage is constant, then the armature voltage and the field strength will be constant. This principle, when applied to both ac and dc motors, is the reason why the motor shaft rotates. Series motors which are mainly used for traction work are easily available in pairs. Hence dc shunt generator is called constant voltage generator. One of these two machines is operated as a generator to supply the mechanical power to the motor.
May 30, 2017 speed control of dc shunt motor by dr. Voltage can be applied to the terminals of the dc motor or. Speed control of dc shunt motor with field and armature. Assuming stator flux to be linear function of field current, determine the constant kk f. Because the current is dc, there is no induced voltage in the rotor circuit and no resulting rotor current. Load test on singlephase transformer and three phase transformers. As resistance increased, the value of the field current will reduce. One machine runs normally as a motor and drives generator whose output is wasted in a variable load r fig. This is very efficient way to find out stray losses in dc shunt motors. The load test on 3phase induction motor is performed to obtain its various characteristics including efficiency. Introduction, basic principle, types of transformer. Load test on dc shunt motor unicon instruments exporter.
Now in this article we are going to discuss about retardation test on dc machines. Swinburnes test for dc machines in this technique, the dc generator or dc motor is run as a motor at no load. In this method, a brake is applied to a watercooled pulley mounted on the motor shaft as shown in fig. So the load test could be performed in two ways ie, by direct loading by indirectly loading in case of direct loading the motor is provide. The shunt is generally used to protect the speed controller from a load drawing too much current, or to limit the speed of the attached motor. Swinburnes test method for testing dc shunt motor for a d. The electric braking of a dc motor is of three types, i rheostatic or dynamic braking, ii plugging or reverse current braking and iii regenerative beaking. Direct method of testing of dc machine, also known as brake test. Free power how to convert an old washing machine into a water powered. Armature reaction, separately excited and self excited generators, load characteristics of shunt, principle of operation, speed control of d. Since load is very small in a shunt motor, armature current is also very low. The positive torque corresponds to the motoring operation. Brake test in one of the most simple way of finding efficiency of any kind of dc machine.
Shunt motor is a special type of dc motor which runs at. The torque speed characteristics separate by excited shunt of the machine under dynamic braking mode is as shown in fig. Brake test on dc shunt motor free download as word doc. Schematic diagram for hopkinsons test on dc machine. Speed of a shunt dc motor can be easily controlled. Dc drives offer the ability to control the speed and torque of heavyduty dc motors in various industrial and other similar applications. Basic configuration of a permanent magnet dc motor is very similar to that of a normal dc motor. Dc injection braking provides a quick and smooth braking action on all types of loads, including high speed and highinertia loads. It is, therefore, apparent that the shunt motor should run at a reasonably constant speed. Swinburnes test is the most commonly used and simplest method of testing of shunt and compound wound dc machines which have constant flux. Basically, a dc voltage is applied to the stator windings of a 3phase im. What you need is a variable dc power supply for this you need to know the ratings of the motor. C motor is the one of common application for industrial.
The principle of the dc motor relies on the concept of commutation. The connection diagram of dynamic braking of dc shunt motor is shown below. Motors, electrical engineering multiple choice questions objective type questions, mcqs, with question and answers, download free pdf, electrical engineering, multiple choice questions, objective type questions, electrical engineering short notes, rapid fire notes, best theory. Shunt wound brushed dc motors are typically used in applications that require 5 or more hp such as industrial and automotive applications. Dc motors applied for the momentarily deliver rated around three or more times from their torque.
Brake test is also a method of finding efficiency of dc motors. Theory the efficiency of the dc machine can be accurately determined by the regenerative method, normally known as hopkinsons test. The connection diagram of shunt motor braking with self and separate excitation is shown in the figure below. Lathes, drills, boring mills, shapers, spinning, and weaving machines series motor. 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. One of these two machines is operated as a generator to supply the mechanical power to the motor and the other is operated as a motor to drive the generator. To determine the efficiency of the given dc shunt motor by conducting load test. Applied voltage 200 v line current 30 a calculate the output power and the efficiency. The first type, is the permanent magnet brush dc motor. Brake test also called as direct loading test of testing the motor.
The machine is running as a motor at rated voltage and speed. Spring balance reading 10 kg and 35 kg diameter of the drum 40 cm speed of the motor 950 r. This commutator and brush connection always keep the direction of the current and the direction of the magnetic field consistent. Brake test on dc shunt motor electric motor electrical.
A permanent magnet dc motor also works on the same principle. Apparatus range type quantity 1 ammeter 020a mc 1 2 voltmeter 0300v mc 1 3 rheostat 1250. Because loading will be applied directly on shaft of the motor by means of a belt and pulley arrangement. Therefore, mechanical loss can be assumed to remain same from no load to full load. The speed and the current to the rotor are inversely proportional. Brake test shunt motor theory brake test shunt motor viva with answers lab manual direct loading test shunt motor speed control shunt motor. Magnetization characteristics of dc shunt generator.
Fields test for series motor this test is applicable to two similar series motors. The high number of turns allows a strong magnetic field to be generated, but the smaller gauge wires provide a high resistance and limit the current flowing through the shunt coil. A belt around the air cooled pulley has its end attached to the spring balance s1 and s2. Title of the experiment page no 7 retardation test on dc shunt motor.
This is also well known that the dc machines can be used as a generator as well as as a motor, their is the difference of operation in both case i. Mar 14, 2016 laboratory explanation of break test on dc shunt motor. In an ac induction motor, when the ac voltage is removed, the motor will coast to a standstill over a period of time, since there is no induced field to keep it rotating. Characteristics of dc shunt motor experiment youtube. Electrical machines 1 pdf notes em 1 pdf notes smartzworld. Retardation test is also called as running down test. In the previous articles we have seen brake test, hopkinsons test which are essential to find out dc machine efficiency. Assuming the spring balance to be calibrated in kilogram. As compared to permanent magnet brushed dc motors, shunt wound brushed dc motors have no loss of magnetism and are more robust.
The following readings are obtained when doing a load test on a d. Open circuit characteristic occ of dc shunt generator 2. In this test we get total stray losses nothing but combination of. As such, the field windings and armature are connected in a parallel combination, and in electrical terminology a parallel combination is known as a shunt. This paper discusses the speed and torque control of a shunt dc motor through matlab simulink simulations. Generally, this test can be done for the low rated dc machines. What is dynamic braking or rheostatic braking of dc motor. To draw the performance characteristics of the given dc shunt motor by conducting load test. It is supplied with one ms powder coated electrical panel fitted with high insulation bakelite sheet. Dc machines can be tested by three different methods namely direct method, indirect method and regenerative method. It is a machine which converts electrical energy into mechanical energy. This test overcomes the drawback of swinburnes test, which. The connection diagram for dc shunt machine is shown in the figure below. Aug 03, 2018 hopkinsons test is another useful method of testing the efficiency of a dc machine.
The characteristics of a shunt motor reveal that it is an approximately constant speed motor. Scribd is the worlds largest social reading and publishing site. To obtain the performance characteristics of a dc shunt motor by load test. This is the complete theory of brake test on dc shunt motor including laboratory manual. In a shunt motor, the field winding, as we ll as the armature winding, is connected in parallel shunt directly to the dc supply lines. When the losses of dc machine wellknown, then we can find the efficiency of a dc machine in advance at any desired load. No load test on dc shunt generator 1 connect the circuit as shown in figure 1 with switches s1 and s2 open. Before starting the experiment the motor field rheostat must be at minimum position and generator field rheostat must be at maximum position. It also include with dynamic braking function or regenerative braking to obtained with dc motors for quick stops application. Dc starter face plate type suitable for above motor. As you know that the construction of any type of dc motor is very similar to a dc generator. Brake test, swinburnes test, hopkinsons test or back to back test, retardation test or running test, fields test, applications of dc motors.
Hopkinsons test is another useful method of testing the efficiency of a dc machine. For dynamic braking, the series motor is disconnected from the supply. In mechanical system, speed varies with number of task so speed control is necessary to do mechanical work in a proper way. Since they are connected in parallel, the armature and field windings are exposed to the same supply voltage. Jul 11, 2019 a dc shunt motor also known as a shunt wound dc motor is a type of selfexcited dc motor where the field windings are shunted to or are connected in parallel to the armature winding of the motor. When a shunt dc motor reaches its full speed, the armature current is directly related to the motor load. Swinburnes test and speed control of dc shunt motor. Connects the armature and fields windings shunt and series combination give characteristics both shunt and series dc. In this test the efficiency of the machine at any load is predetermined. Electrical machines 1 viva questions and answers in this post we had collected some of the most frequently asked electrical machines 1 viva questions with detailed answers.
In addition to the above eight experiments, at least any two of the experiments from the fo owing list are required to be conducted. Thus the speed of dc motor is given by, eb v i a r a. To find the various parameters such as torque, input power, output power etc. One end of the rope is fixed to the floor via a spring balance s and a known mass is suspended at the other. Introduction to dc motors 4 assuming shunt connected dc motor, compute back emf, field resistance, armature resistance, field loss, armature loss, power efficiency, starting torque, and noload speed.
The brake test is the one kind of load test on dc shunt motor. It is a full load test and it requires two identical machines which are coupled to each other. Dec 29, 2015 the shunt field windings of a dc shunt motor are made of smaller gauge wire, but they have many more turns than a serieswound dc motor. Third is the serieswound dc motor and fourth is the compoundwound brushed dc motor which is a combination of both the shunt and series wound brushed dc motors. C motor field windings 25092011 by lemau 2 comments d. In case of dc shunt motors, armature is disconnected from the supply and a rheostat variable resistor is connected across it. Analog ammeter and voltmeter are provided on the front panel sheet. What is a dc shunt motor and its advantage and disadvantage. Depending on the motors design a tachometer system should be included. One end of the rope is fixed to the floor via a spring balance s and a known mass is suspended at the other end.
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