In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. When inspecting a wound rotor motor and the rotor lead is the point of failure, the transient caused by a rapid restrike is a strong contender for the root cause of the failure. Some sections may explain explicitly between the three configurations. Adjusting the resistance allows control of the speedtorque characteristic of the motor. The windings receive current through some kind of slipring arrangement. The stator of slip ring induction motor is very much the same as that of the squirrel cage induction motor, but the construction of its rotor is very much different. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. It is well known that induction motor testing standards vary significantly in their defined methodologies, instrumentation accuracy, and testing procedures. A woundrotor motor, also known as slip ringrotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. Today, i am going to tell you about a wound rotor induction motor, which is also a type of 3 phase induction motor. Motor runs smoothly as the magnetic hum is reduced b. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below.
Connect the resistor loading rack at the generator armature terminals. And determine the full load regulation of a three phase synchronous generator by synchronous impedance method 3. Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. One benefit to doing so is that, if an eccentric air gap is suspected, the electrical noise will still be present. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor.
Induction motor testing and evaluation summary as energy costs rise, more emphasis is being placed on determining the health of large inductive motors. Each motor is given a routine test as required by bs4999, as59 or nema mg 1. But the rotor construction differs with respect to the type of motor. Record all nameplate information for the induction motor. Some sections may explain explicitly between the three configurations, but have different requirements for each. Dec 30, 2018 testing of induction motor december 30, 2018 february 24, 2012 by electrical4u demand of energy is growing day by day and along with it cost of energy rising abruptly, so now it is necessary that the health of large motors which consumes maximum power should be taken care off.
Slip frequency is calculated by subtracting the actual operating speed of the motor from the synchronous speed. Slipring induction motor also known as rotor resistance start motor. The main difference in a slip ring induction motor is on the rotor construction and usage. I will tell about the construction of a wound rotor later in this article. Testing motors with motor circuit evaluation detecting rotor defects with mce testing technology is one of the newest forms of rotor testing in todays market.
Dec 01, 2017 slipring induction motor also known as rotor resistance start motor. The slip ring motor has very little application in industries. It utilizes a low voltage, high frequency signal to measure the inductance l reading for each of the stator windings in a threephase ac induction motor. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrelcage rotor. When the 3 phase supply is provided to the stator, a magnetic field is produced which rotates the rotor and motor starts. Telecommunication engineering, southwest jiaotong university, china, 2005 thesis submitted for the degree of masters of engineering science in school of electrical and electronic engineering the university of adelaide, australia august 2010. All motors comply with the following indian and international standards. By far the most commonly used ac motor is the induction motor. Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound rotors having three windings each connected in star. Induction machines are considered relatively reliable and robust due to their simple design and welldeveloped manufacturing technology.
Slipring collector tester a slip ring in electrical engineering terms is a method of making an electrical connection through a rotating assembly. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. If the external controller is set at zero resistance, the motor operates almost exactly the same as the squirrelcage motor, since the rotor is shortcircuited. Starters limit the starting current in an induction motor which goes 56 times of full load current as slip remains 1. O remove as much dust as possible with a vacuum cleaner. Abstract condition monitoring of slipring induction motor have been a challenging task. Explain starting methods of 3 phase induction motor. Slip ring induction motor working principle electrical. The stationary part of the induction motor windings stator connects to. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. The oil ring lubrication process can be easily modified for flood lubrication. What happens if slip rings are short circuited in a 3 phase.
Blow dry air though the rotor and the stator in both directions, i. Stator winding can be either star or delta connected depending upon the design. What are the type of starter used for slip ring induction. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Depending on type of workload there are various type of starters for a slip ring induction motor.
Noload and blocked rotor test on an induction machine aim. For a motor with slip rings, measure and record the collector ring wear and concentricity. Pdf rotor side control of high power slip ring induction motor. Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. Slip in electrical induction motors engineering toolbox. The rotor of the slip ring induction motor is also cylindrical or constructed of lamination. Wound rotor induction motor the engineering projects. The speed of an ac motor depends on the frequency of the input power and the number of poles for which the motor is wound. Note locations relative to a reference point on the collector ring where runout is excessive. Slip ring motors electrical calculations and induction. Draw the torque slip characteristics of 3 phase slip ring induction motor. Mixedfrequency testing of induction machines using inverters.
The tendency of the rotor teeth to remain under the stator teeth due to direct magnetic attraction is reduced. Learn more about the construction and operation of a slip ring induction motor. The basic idea of an electric motor is to generate two magnetic fields. You can find manuals and other product documents in pdf format on the internet. If it was not caused by an operator tapping the button.
The load test on induction motor is performed to compute its complete performance i. The slip ring rotor chamber of the ic 411 slip ring induction motor is separated by what is known as a labyrinth seal, which prevents contamination from coal dust. To study and measure direct and quadrature axis reactance. In addition to conventional squirrel cage rotor testing methods such as the growler test, also covered will be techniques such as the use of a core loss tester, high current excitation, and spectrum analysis of vibration. Slip ring testing slipring collector tester a slip ring in electrical engineering terms is a method of making an electrical connection through a rotating assembly. Percent slip is a way to measure the speed performance of an induction motor. Squirrel cage induction motors a stator construction. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. The rotor of an induction motor can be a squirrel cage rotor or wound. Connection for load testing of a threephase induction motor. Whats worse than a slip ring flashover on a critical wound rotor motor.
This paper aims to represent routine test performing in three phase induction motor. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque. Generally, induction motor provides low starting torque as compared to d. The static kramerdrive converts the slip power of an induction motor into ac power and supply back to the line. Slip is also expressed as a dimensionless ratio calculated as.
Supplement acs800 igbt based slip power recovery system. Rotating electrical machinery natural graphite brush for slipring in wound rotortype induction motor application information. The construction of stator of the induction motor is almost the same as other motors. Slip rings, also called rotary electrical interfaces, rotating electrical connectors, collectors, swivels, or electrical rotary joints, are commonly found in electric motors, electrical generators for ac systems. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. An optional test is to connect the stator leads together, and run the motor by energizing the rotor leads at the rated secondary voltage.
So the main idea behind motor maintenance is to prevent breakdown rather than repairs them. Examine the slip ring helical groove edge chamfering. Smooth starting of slip ring induction motors article pdf available in ieee transactions on energy conversion 124. Some changes in the stator may be encountered when a slip ring motor is used in a cascaded system, as the supply for the slave motor is controlled by the supply from the rotor of the other slip ring motor with external resistance mounted on its rotor. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. Gradually apply three phase voltage across motor stator terminals via the autotransformer d. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. Induction motor parameters locked rotor test the locked rotor. The slip ring or wound rotor motor is an induction machine where the rotor comprises a set of coils that are terminated in sliprings to which external impedances can be connected.
A low current supply mixedfrequency testrig has been proposed. Testing 100% routine test quality is emphasised at each step as a motor proceeds through each stage of design, assembly and testing. Selecting the correct squirrel cage motor to replace a slip ring motor has been challenging for those doing the selection. Slip ring induction motor fundamentals pnpntransistor. The slip ring rotor chamber has two modification openings. Three phase slip ring induction motor my tech info. It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. Induction motor is one of the most important motor used in industrial applications. Diagnostics of rotor and stator problems in industrial induction motors by fang duan b. When the motor is started the total external resistance get added in the rotor winding resistance and the value of the resistances get gradually decreased with th. Lecture 6 three phase induction motors cairo university. A wound rotor, has a 3phase winding similar to the stator winding.
They are especially suitable for heavy load inertia applications. Also record the manufacturers acceptable collector ring runout. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. So, this motor is used in applications like lifts, pumps, mills where we require high starting torque. The rotor winding terminals are connected to three slip rings which turn with the rotor. There are two types of induction motors, one with wound type rotor, also called slip ring motor and another one with squirrelcage rotor. Slipring induction motor connection and testing people education online. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements.
But at the starting of the induction motor, starting current is very large which may damage motor windings. The rotor terminals are connected to three slip rings which turn with the. Slip ring motor conversion to vsd driven standard squirrel. Number of poles, frequencies and synchronous induction motor speed.
Over a number of years slip ring motors have largely been replaced by standard squirrel cage ac induction motors, often in conjunction with ac variable speed drives vsds. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. The stator or the stationary part consists of three phase winding held in place in the slots of a laminated. Testing of a squirrel cage rotor requires some understanding of how the rotor functions. Note down the machine ratings and calculate rated current of the machine noload test. This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. Once the rotor reaches final speed, the rotor poles get switched to a short circuit, thus becoming electrically the same as a squirrel cage rotor.
Testing of induction motor december 30, 2018 february 24, 2012 by electrical4u demand of energy is growing day by day and along with it cost of energy rising abruptly, so now it is necessary that the health of large motors which consumes maximum power should be taken care off. In order to start a slip ring motor, the accelerating torque has to be sufficiently higher than the resisting torque. According to the execution of brushes and sliprings the motors are classified into two. Motor current monitoring and analysis mcsa is a straight forward tool to diagnosing problems with large inductive motors. The slip ringsbrushes allow external resistors to be connected in series with the winding.
Speed control of threephase slip ring induction motor by rotor resistance. For load sharing to take place automatically, the motor speed should drop considerably as the load increases and this is ensured by using a motor having a high fullload slip, say for example 10%. The 3phase set of currents, each of equal magnitude and with a phase. A squirrelcage motor with this type of rotor construction is called nemadesign class d. The rotor will constantly be turning to align its magnetic field with that of the stator field. What happens if slip rings are short circuited in a 3. Higher is the inertia, higher has to be the accelerating torque, otherwise the start will be very long and the motor can be damaged by the heating. Disconnect any mechanical load connected to the induction motor. The mcemax performs tests on electric motors while the motor is running or when. May 20, 2014 2 rocar arm field armature commutator carbon brush with holder slipring commutator centre fugal swit duration. Slip ring induction motor application slip ring induction motor provides high starting torque. This is easiest to visualize at motor startup, when the rotor is not yet turning. If the slip ring induction motor is started with all the slip rings or the rotor terminals.
Three phase induction motors electric motors bharat bijlee. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. On request, motors can also be constructed and tested according to other. The induction motor is started by itself that we know.
The rotor of an induction motor is like the secondary winding of a transformer, with the motor stator being the primary. The stator is the same as is used with a standard squirrel cage motor. The slip power recovery scheme also plays a proactive role as there can be substantial savings of energy in case of a wound rotor induction motor as the slip power recovered can be used to drive. Testing facility iec has adopted testing procedure from csa, ieee 112method b i. Since here we are talking about maintenance of induction motor, and it is of two types. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. Slip ring induction motor working principle electrical mastar. In this test, the alternator is run with the prime mover i. Control of motorcharacteristics by squirrelcage rotordesign.
Slip ring motor fundamentals bright hub engineering. Show full abstract to determine the margin of stability and. With each load value, record the reading of v t, i a, w 1, w 2, v dc the speed n and i dc 10 amp scale in table 5. Slipring induction motor connection and testing youtube. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. The ld language enables the description of tests and modifications of. The test results with an induction motor load reveal that the proposed method is able. Pdf design and analysis of drive system with slip ring. Safe area motors motors for general application cga1d standard squirrel cage tefc motors. Operating characteristics of a woundrotor slipring.
The slip power is the air gap power between the stator and the rotor of an induction motor which is not converted into mechanical power. Department of electrical engineering national institute of. First noload test the noload test, like the open circuit test on a transformer, gives information about exciting current and rotational losses. If it was not caused by an operator tapping the button, it could be a weak magnetic holding coil allowing. Condition monitoring of slipring induction motor ijirae.
This is easiest to visualize at motor startup, when the rotor. Generally we all are know induction motor is most widely used motor in industrial. Wound rotor induction motors ac motors electronics textbook. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. Home operating characteristics of a woundrotor slipring induction motor fig. In the induction motors used in lift and hoists, you will see a type of rotor called a slip ring rotor, whereas in most of the other applications you. The terminals of the rotor windings of the slipring motors. Because of the large rotor resistance, this motor has a pullout torque occurring at a high slip, and its starting torque is quite high. The slip ring induction motor has two distinctly separate parts, one is the stator and other is the rotor. Diagnostics of rotor and stator problems in industrial. The test is performed by applying balanced rated voltage on the stator. Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. Starting of slip ring induction motor explained in an easy.
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