Speed control of three phase slip ring induction motor. There are two types of losses occur in three phase induction motor 1. A slip ring motor also requires a larger space for the motor and its. If it was not caused by an operator tapping the button, it could be a weak magnetic holding coil allowing.
But the rotor construction differs with respect to the type of motor. Nov 02, 2016 load test on 3 phase induction motor 1. Motor current monitoring and analysis mcsa is a straight forward tool to diagnosing problems with large inductive motors. If the slip ring induction motor is started with all the slip rings or the rotor. Record the specifications of the induction motor im arrange and measure the resistance of the load rack in the same manner as in the previous experiment for 6 different readings. The speed of a pair of slipring motors can be controlled by a cascade connection, or concatenation. Large slip ring motor drives, termed slip energy recovery systems, some still in use, recover energy from the rotor circuit, rectify it, and return it to the power system using a vfd. Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. Dec 01, 2017 slipring induction motor also known as rotor resistance start motor.
Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound rotors having three windings each connected in star. During this test, the motor is operated at rated voltage and frequency and normally loaded mechanically by brake and pulley arrangement. Diagnostics of rotor and stator problems in industrial. No load test of induction motor your electrical guide. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. To conduct the load test on 3phase 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. Note that applying brake on any motor amounts to loading it. A reduced voltage, nearly 15% of normal voltage is applied to the stator winding. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. What is the break test on a 3phase induction motor. Noload and blocked rotor test on an induction machine aim theory.
A slip ring motor is expensive, as are its controls, compared to a squirrel cage motor. And determine the full load regulation of a three phase synchronous generator by synchronous impedance method 3. 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 full load slip, say for example 10%. What external resistance per phase must be added in the rotor circuit so that the motor now runs ate a slip of 17. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. Note down the machine ratings and calculate rated current of the machine no load test. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. 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 no load test of an induction motor is similar to the opencircuit test of a transformer.
These tests are performed to check the electrical or mechanical defects of the induction motor. A squirrel cage motor is thus preferred to a slipring motor. The motor is not connected from its load, and the rated voltage at the rated frequency is applied to the stator to run the motor without a load. The load test on induction motor is performed to compute its complete performance i. Therefore slip ring induction motors are generally employed where load requires high starting torque or good speed control. Abstract in this project, two kinds of induction motor faults, stator short circuit fault and broken rotor bar fault, are investigated by using motor current signature analysis mcsa. Starting of slip ring induction motor explained in an easy.
As its name indicates stator is a stationary part of induction motor. Note down the machine ratings and calculate rated current of the machine noload test. The no load current i 0 is simulated by a pure inductive reactor x 0 taking the magnetizing component i and a noninductive resistor r 0 carrying the core loss. For large motors, the slip is less than 1% because an induction motor consists of short circuit rotor winding having small resistance therefore small slip will induce the large current in the rotor which can produce sufficient torque. Disconnect any mechanical load connected to the induction motor. Machine will rotate at almost synchronous speed, which makes slip nearly equal. Mixedfrequency testing of induction machines using inverters. Dec 30, 2018 these tests are performed to check the electrical or mechanical defects of the induction motor. Noload and blocked rotor test on an induction machine aim. At full rated load, slip varies from more than 5% for small or special purpose motors. To determine the equivalent circuit parameters of an induction motor. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. A stator winding is placed in the stator of induction motor and the three phase supply is given to it. Speed control of threephase slip ring induction motor by rotor resistance control.
Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. Therefore, small current is applied to the machine due to which there is a fall in the statorimpedance value and rated voltage is applied across the magnetizing branch. The aim behind the development of the project is to limit the current at starting of motor and to develop the high starting torque. Three phase slip ring induction motor my tech info. The slip ring motor has very little application in industries. 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. Slipring induction motor connection and testing youtube. It also requires meticulous and periodic maintenance of the brushes, brush gear, sliprings, external rotor resistances etc.
A slip ring is also used in applications where the load require good speed control. The test is performed by applying balanced rated voltage on the stator. Induction motors generally will have low starting torque compared to dc series motor. Number of poles, frequencies and synchronous induction motor speed. Induction motor parameters locked rotor test the locked rotor. Wound rotor induction motors ac motors electronics textbook. If an induction motor is tested at various loads and the stator. The slip ring induction motor has two distinctly separate parts, one is the stator and other is the rotor. Load test on single phase squirrel cage induction motor aim. Deducing rotor inertia and torquespeed curves of the motor. Learn more about the construction and operation of a slip ring induction motor.
The slip ring rotor chamber has two modification openings. It also requires meticulous and periodic maintenance of the brushes, brush gear, slip rings, external rotor resistances etc. 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. Perform no load and block rotor test on 3 phase induction motor. The stator circuit model of an induction motor consists of a stator phase winding resistance r 1, stator phase winding leakage reactance x 1 as shown in the circuit diagram below. A slipring motor is expensive, as are its controls, compared to a squirrel cage motor. Theory of no load test of induction motor the impedance of magnetizing path of induction motor is large enough to obstruct flow of current. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Compute torque, output power, input power, efficiency, input power factor and slip for every load.
Full load slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. 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. To study and measure direct and quadrature axis reactance. 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%. No load and blocked rotor test on 3 squirrel cage induction. Slip ring motor fundamentals bright hub engineering. Slip ring induction motor advantages disadvantages and. An 8 pole, 50 hz slip ring induction motor runs at a slip of 2. In this test, a rated, balanced ac voltage at a rated frequency is applied to the stator while it is running at no load. Brake test is basically a load test of induction motor. There are different methods of starting of 3phase slipring induction motor. In this test, the alternator is run with the prime mover i. To conduct the load test on single phase squirrel cage induction motor and to draw the performance characteristics curves. When a motor starts to rotate the slip is 100 % and the motor current is at maximum.
Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. If the motor slip is known, the rotor speed can be expressed by the equation. This test is performed on only one motor of a batch of similar motors and called a type test. Load test of induction motor to determine how speed, efficiency, power factor, stator current, torque and slip of an induction motor vary with load, the load test on an induction motor is performed. The no load test is similar to the open circuit test on a transformer. Record all nameplate information for the induction motor. The construction of stator of the induction motor is almost the same as other motors.
Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below. Slip ring induction motor fundamentals pnpntransistor. Variable losses constant or fixed losses fixed losses are considered to remain constant over normal working range of a induction motor. Therefore slip ring induction motors are generally employed where load. First no load test the no load test, like the open circuit test on a transformer, gives information about exciting current and rotational losses. A squirrel cage motor is thus preferred to a slip ring motor. The voltage is so adjusted to allow full load current to the stator windings. The noload test of an induction motor is similar to the opencircuit test of a transformer. Three phase slip ring induction motor drive with slip power control analysis for different load torque using microsoft excel as software tool. Generally, induction motor provides low starting torque as compared to d.
Gradually apply three phase voltage across motor stator terminals via the autotransformer d. 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. They are employed in hoists, elevators, compressors, printing presses, large ventilating fans, loads requiring speed control such as for driving lifts and pumps. Induction motor testing and evaluation summary as energy costs rise, more emphasis is being placed on determining the health of large inductive motors. Slip in electrical induction motors engineering toolbox. No load test and locked rotor test in an induction motor my. Circuit diagram for no load and blockedrotor test on 3 phase induction motor a. If it was not caused by an operator tapping the button. 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. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. The rotor resistance per phase of the winding is 0. Load test on threephase squirrel cage induction motor.
To obtain the variation of no load power and current and blocked rotor power and current with changes in the applied voltage to the stator. Effects of rotor asymmetry conference paper pdf available june 1997 with 3,082 reads how we measure reads. There are different methods of starting of 3phase slip ring induction motor. If i sc full load current of motor, then p sc is total copper loss on full load. Department of electrical engineering national institute of. Pdf three phase slip ring induction motor drive with slip power.
Aug 25, 2018 theory of no load test of induction motor the impedance of magnetizing path of induction motor is large enough to obstruct flow of current. They are especially suitable for heavy load inertia applications. A variable inertia test for full load temperature rise testing of induction machines has been. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. During this test, the motor is operated at rated voltage and frequency and normally loaded mechanically by brake and pulley arrangement from the observed data, the performance can be.
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