Slip ring motor conversion to vsd driven standard squirrel. Speed control of threephase slip ring induction motor by rotor resistance. Diagnostics of rotor and stator problems in industrial induction motors by fang duan b. One benefit to doing so is that, if an eccentric air gap is suspected, the electrical noise will still be present. Blow dry air though the rotor and the stator in both directions, i. Induction motor parameters locked rotor test the locked rotor. 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. Slip frequency is calculated by subtracting the actual operating speed of the motor from the synchronous speed. The load test on induction motor is performed to compute its complete performance i. Generally we all are know induction motor is most widely used motor in industrial. Three phase induction motors electric motors bharat bijlee. The rotor will constantly be turning to align its magnetic field with that of the stator field. Slip ring induction motor working principle electrical. In this test, the alternator is run with the prime mover i.
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. The rotor of an induction motor is like the secondary winding of a transformer, with the motor stator being the primary. Note locations relative to a reference point on the collector ring where runout is excessive. Record all nameplate information for the induction motor. Noload and blocked rotor test on an induction machine aim. Induction motor is one of the most important motor used in industrial applications. 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. 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 to determine that it is. You can find manuals and other product documents in pdf format on the internet. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. 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%. 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.
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. Slip ring induction motor working principle electrical mastar. This paper aims to represent routine test performing in three phase induction motor. Slipring collector tester a slip ring in electrical engineering terms is a method of making an electrical connection through a rotating assembly. The slip ringsbrushes allow external resistors to be connected in series with the winding. This is easiest to visualize at motor startup, when the rotor. What happens if slip rings are short circuited in a 3. Adjusting the resistance allows control of the speedtorque characteristic of the motor. 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. Mixedfrequency testing of induction machines using inverters. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. Slip ring induction motor application slip ring induction motor provides high starting torque.
Selecting the correct squirrel cage motor to replace a slip ring motor has been challenging for those doing the selection. Squirrel cage induction motors a stator construction. The stationary part of the induction motor windings stator connects to. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrelcage rotor. The squirrel cage induction motor is the most popular type of ac motor. In order to start a slip ring motor, the accelerating torque has to be sufficiently higher than the resisting torque. The rotor terminals are connected to three slip rings which turn with the. 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. I will tell about the construction of a wound rotor later in this article. Department of electrical engineering national institute of. Today, i am going to tell you about a wound rotor induction motor, which is also a type of 3 phase induction motor. Slipring induction motor connection and testing youtube. The rotor of the slip ring induction motor is connected to the external resistances.
Smooth starting of slip ring induction motors article pdf available in ieee transactions on energy conversion 124. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. The test results with an induction motor load reveal that the proposed method is able. Supplement acs800 igbt based slip power recovery system. Dec 01, 2017 slipring induction motor also known as rotor resistance start motor. 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. You should also make a dc measurement of stator winding linetoline resistance using a dmm.
The construction of stator of the induction motor is almost the same as other motors. All motors comply with the following indian and international standards. 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. So the main idea behind motor maintenance is to prevent breakdown rather than repairs them. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. First noload test the noload test, like the open circuit test on a transformer, gives information about exciting current and rotational losses. Starting of slip ring induction motor explained in an easy.
Generally, induction motor provides low starting torque as compared to d. Wound rotor induction motor the engineering projects. 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. A low current supply mixedfrequency testrig has been proposed. This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. The induction motor is started by itself that we know. Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. The induction motor stator resembles the stator of a revolving field, three phase alternator. Starters limit the starting current in an induction motor which goes 56 times of full load current as slip remains 1. 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. What happens if slip rings are short circuited in a 3 phase. Motor current monitoring and analysis mcsa is a straight forward tool to diagnosing problems with large inductive motors.
Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. And determine the full load regulation of a three phase synchronous generator by synchronous impedance method 3. 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. It is well known that induction motor testing standards vary significantly in their defined methodologies, instrumentation accuracy, and testing procedures. Connect the resistor loading rack at the generator armature terminals. A squirrelcage motor with this type of rotor construction is called nemadesign class d. If the slip ring induction motor is started with all the slip rings or the rotor terminals. Connection for load testing of a threephase induction motor. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles.
The basic idea of an electric motor is to generate two magnetic fields. Each motor is given a routine test as required by bs4999, as59 or nema mg 1. Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound rotors having three windings each connected in star. Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. 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. Testing facility iec has adopted testing procedure from csa, ieee 112method b i. Disconnect any mechanical load connected to the induction motor.
Percent slip is a way to measure the speed performance of an induction motor. Slipring induction motor also known as rotor resistance start motor. Operating characteristics of a woundrotor slipring. By far the most commonly used ac motor is the induction motor. Home operating characteristics of a woundrotor slipring induction motor fig. 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. Also record the manufacturers acceptable collector ring runout. 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. They are especially suitable for heavy load inertia applications. So, this motor is used in applications like lifts, pumps, mills where we require high starting torque. To study and measure direct and quadrature axis reactance. The 3phase set of currents, each of equal magnitude and with a phase.
What are the type of starter used for slip ring induction. The slip ring motor has very little application in industries. The rotor of an induction motor can be a squirrel cage rotor or wound. But at the starting of the induction motor, starting current is very large which may damage motor windings. The ld language enables the description of tests and modifications of. According to the execution of brushes and sliprings the motors are classified into two.
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. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. May 20, 2014 2 rocar arm field armature commutator carbon brush with holder slipring commutator centre fugal swit duration. The static kramerdrive converts the slip power of an induction motor into ac power and supply back to the line. A wound rotor, has a 3phase winding similar to the stator winding. The windings receive current through some kind of slipring arrangement. Whats worse than a slip ring flashover on a critical wound rotor motor. Induction machines are considered relatively reliable and robust due to their simple design and welldeveloped manufacturing technology. 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.
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. Stator winding can be either star or delta connected depending upon the design. The slip ring induction motor has two distinctly separate parts, one is the stator and other is the rotor. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. The tendency of the rotor teeth to remain under the stator teeth due to direct magnetic attraction is reduced. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. The oil ring lubrication process can be easily modified for flood lubrication.
The main difference in a slip ring induction motor is on the rotor construction and usage. For a motor with slip rings, measure and record the collector ring wear and concentricity. 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. Since here we are talking about maintenance of induction motor, and it is of two types. Slip ring motors electrical calculations and induction. Some sections may explain explicitly between the three configurations, but have different requirements for each. Draw the torque slip characteristics of 3 phase slip ring induction motor.
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. Explain starting methods of 3 phase induction motor. Safe area motors motors for general application cga1d standard squirrel cage tefc motors. Show full abstract to determine the margin of stability and.
Abstract condition monitoring of slipring induction motor have been a challenging task. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. Control of motorcharacteristics by squirrelcage rotordesign. The stator is the same as is used with a standard squirrel cage motor. Condition monitoring of slipring induction motor ijirae. 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. Pdf design and analysis of drive system with slip ring. Gradually apply three phase voltage across motor stator terminals via the autotransformer d. Number of poles, frequencies and synchronous induction motor speed. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. But the rotor construction differs with respect to the type of motor. Depending on type of workload there are various type of starters for a slip ring induction motor.
Some sections may explain explicitly between the three configurations. 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. The terminals of the rotor windings of the slipring motors. If it was not caused by an operator tapping the button, it could be a weak magnetic holding coil allowing. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals.
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. 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. The mcemax performs tests on electric motors while the motor is running or when. Note down the machine ratings and calculate rated current of the machine noload test. Slip ring induction motor fundamentals pnpntransistor. Slip in electrical induction motors engineering toolbox.
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. Rotating electrical machinery natural graphite brush for slipring in wound rotortype induction motor application information. Diagnostics of rotor and stator problems in industrial. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below. An optional test is to connect the stator leads together, and run the motor by energizing the rotor leads at the rated secondary voltage. If it was not caused by an operator tapping the button. Because of the large rotor resistance, this motor has a pullout torque occurring at a high slip, and its starting torque is quite high. Pdf rotor side control of high power slip ring induction motor. Testing of a squirrel cage rotor requires some understanding of how the rotor functions. On request, motors can also be constructed and tested according to other.
Testing 100% routine test quality is emphasised at each step as a motor proceeds through each stage of design, assembly and testing. O remove as much dust as possible with a vacuum cleaner. The rotor of the slip ring induction motor is also cylindrical or constructed of lamination. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Examine the slip ring helical groove edge chamfering.
It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. 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. Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. Learn more about the construction and operation of a slip ring induction motor. The rotor winding terminals are connected to three slip rings which turn with the rotor. 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. Squirrel cage induction motor requires significantly less maintenance as it does not contain brushes, commutators, slip rings. 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. This is easiest to visualize at motor startup, when the rotor is not yet turning. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Three phase slip ring induction motor my tech info. Wound rotor induction motors ac motors electronics textbook. Slip is also expressed as a dimensionless ratio calculated as.
Lecture 6 three phase induction motors cairo university. The stator or the stationary part consists of three phase winding held in place in the slots of a laminated. Slip ring motor fundamentals bright hub engineering. When the 3 phase supply is provided to the stator, a magnetic field is produced which rotates the rotor and motor starts. The test is performed by applying balanced rated voltage on the stator. The slip ring rotor chamber has two modification openings.