In this circuit, four steps of speed control are possible. Speed control of induction motor is possible in two sides. In this paper the speed control problem is considered for an induction motor with wound rotor. Historically, it has been used for hardtostart, high inertia fans, or where power system requirements demand a soft start. The wound rotor induction motor or slip ring motor is widely used for applications requiring speed control or low starting currents. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. Speed control of wound rotor induction motor using rotor. The control of dc machines are found to be more expensive over the rotating machines and. Speed control of wound rotor induction motor using rotor resistance control aim to use variable resistance in the rotor circuit to control wound rotor induction motor speed theory polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith sliprings.
Today, i am going to tell you about a wound rotor induction motor, which is also a type of 3 phase induction motor. From the equation 1 it is clear that the motor speed can be changed by a change in frequency f, a number of poles p, and slip s. Wound rotor induction motors ac motors electronics textbook. Test results of induction motor broken rotor bar fault 1 page v. The speed of induction motor can be varied by changing supply voltage. Rotor as the name suggests it is a rotating part of an electrical machine, in which current is induced by transformer action from rotating magnetic field. Frequency converters, for variable speed control of threephase induction motors. Construction of three phase induction motor electrical4u. Chapter 3 induction motor and different speed control methods page no 3. This method is applicable to squirrel cage induction motor only. Diagnostics of rotor and stator problems in industrial.
The technique of starting woundrotor motors with resistance in the rotor circuit is also used for speedcontrol applications. Rotor resistance controls the speed of wound rotor induction motor. Four separate push buttons permit selection of the operating speed of the motor. Therefore, it is customary to combine them in to a single reactance. Speed control of an induction motor there is a various method of speed control of an induction motor. Wound rotor induction motor the engineering projects. A wound rotor induction motor has a stator like the squirrel cage induction motor. They are commonly used on fans, pumps, conveyors and crane systems. 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. Adjusting the resistance allows control of the speedtorque characteristic of the motor. It is shown that one of simple ways to regulate the speed of wound rotor induction motor is variation of the additional resistance in the rotor circuit. The rotor speed of an induction motor is given by the equation shown below.
This type of rotor has a 3phase, doublelayer, distributed. At lower speeds, either power is wasted in rotor resistances or power is pumped back from the rotor circuit to grid using different standard energy. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below. Speed control of vector controlled induction motors using. The individual forces in the rotor rods combine to form the torque t on the motor. Post glover wound rotor motor resistors wound rotor motors, as opposed to ac induction motors, generate the same torque in both forward and reverse. Speed control of wound rotor induction motors by ac.
We can change the speed at the stator by, changing the supply frequency, changing the supply voltage and changing the number of stator poles. Woundrotor motors, wound rotor induction motors, wound rotor motor. The basic idea of an electric motor is to generate two magnetic fields. When power is supplied to an induction motor at the recommended specifications, it runs. Wound rotor motors deliver speed control of heavy and hightorque loads. The torque developed in this method is proportional to the square of the supply voltage. In this article, we will learn about squirrel cage and slip ring induction motors.
What makes the wound rotor motor a unique induction machine is its rotor. Are there single phase wound rotor induction motors. Jzr2 yzr series ac crane lifting wound rotor slip ring motors. A different behavior is obtained for constant rotor current control. 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. Speed control methods for wound rotor ims electric. Wound rotor induction motor applications how it works wound rotor motors are an extremely versatile breed of induction motors. When the rotor of ims is provided with a wound rotor, speed control is performed by adding a variable resistor to the rotor circuit connecting a power converter to the rotor to introduce or extract power from the rotor. Home operating characteristics of a woundrotor slipring induction motor fig.
Changing rotor slip important to match the motor to the load ensure that a change in motor power gives a desired change in load speed load should have a substantial inertial components inertial torque can carry the load through brief periods when motor torque. Various induction motor speed control methods advantages. Abstract in this project, two kinds of induction motor faults, stator short circuit fault and bro. Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. It consists laminated cylindrical core which has a semiclosed slot at the outer periphery and carries threephase insulated winding.
Wound rotor induction motor is also used in fans, blowers and mixers. The motors are rated according to their primary and secondary windings. An induction motor is practically a constant speed motor, that means, for the entire loading range, change in speed of the motor is quite small. It is possible to combine a dahlander winding with a single. Wound rotor induction motor is used in applications which require smooth start and adjustable speed. In this study, the speed and torque of a wound rotor induction motor wrim have been controlled by adjusting the rotor resistance using a microcontroller.
An843, speed control of 3phase induction motor using. Speed control of wound rotor motors electric motors. If the rotor moved at synchronous speed, then each conductor in the rotor would be moving at the speed of the field. It will be shown that when we choose a synchronous reference frame in which rotor flux lies on the daxis, dynamic equations of the induction motor is simplified and analogous to a dc motor 47. Conclusion the speed control of induction motors is one of the most important engineering problems. Featuring a rugged design, these machines provide the unique ability to gradually bring up to speed highinertia equipment and large loads smoothly and easily.
The conductor and the field would appear stationary and not var. Speed control methods for wound rotor ims electric equipment. Speed of a dc shunt motor can be varied very easily with good efficiency, but in case of induction motors, speed reduction is accompanied by a corresponding loss of efficiency and poor power factor. Be specially designed for energy saving purpose which is totally enclosed and fancooled type. The speed of an electric motor is an important element that depends on many factors. Speed control works well with variable speed loads like elevators and printing presses. The proposed drive system uses a matrix converter to transfer the slip energy from the rotor into the mains instead of using acdcac. Slip energy recovery of a rotorside field oriented.
Operating characteristics of a woundrotor slipring. Speed control of wound rotor induction motor pdf objective. In the case of a squirrel cage induction motor, the rotor resistance is very low so that the current in the rotor is high. The wound rotor motor is particularly effective in applications where using a squirrelcage motor may result in a starting current thats. Wound rotor speed control a time operated controller circuit is shown in figure 44 8. Good performance, such as high safety, energy saving, compact design, low noise, little vibration, big breakaway torque, reliable. Percent slip is a way to measure the speed performance of an induction motor. The speed torque curves of the wound rotor induction motor, 2892016 lutfi alsharif. Recently the performance of woundrotor induction motor has been greatly enhanced by combination of input voltage control and rotor resistance control simultaneously 9, 10. Problems in industrial induction motors by fang duan b. What are the methods to control speed of wound rotor. The rotor will constantly be turning to align its magnetic field with that of the stator field. The motor which employing the wound rotor is known as a slip ring induction motor or phase wound motor.
Induction motors combine outstanding performance with an advanced longlife design. Wound rotor motors are an old system for providing relatively efficient operation of a relatively large e. Synchronous speed is the rate at which the magnetic field rotates. Woundrotor induction motor the magnetizing branch can not be neglected i0 may be 40% of ip due to the air gap for motors greater than 2 hp, the magnetization branch can be shifted to the input terminals for a motor running at a slip s, the rotor speed is ns1s this will modify the values of e1, i1, e2 and i2. Some of the advantages like low cost, rugged design less complex, and easy to maintain ac motors results in many of the industrial operations are performed with the use of ac drives than dc drives.
Record all nameplate information for the induction motor. A 3 phase vsi with a dynamic capacitor is connected in. This type of 3phase induction motor has high starting torque, which makes it ideal for applications where standard nema design motors fall short. The 3phase set of currents, each of equal magnitude and with a phase. Squirrel cage rotor wound type rotor or slip ring type rotor squirrel cage rotor in this type. The torque of an induction motor is the torque produced at the rotor.
This paper investigates rotorside field oriented control of a woundrotor induction motor using the slip energy recovery principle. In three phase induction motor, the power is transferred from stator to. Hcs can also generate reports in html or pdf format. Facts worth knowing about frequency converters k2 drives. Some of the applications of this motor include cranes, mills, hoists and conveyors. Almost 80% of the mechanical power used by industries is provided by three phase induction motors because of its simple and rugged construction, low cost, good operating characteristics, the absence of commutator and good speed regulation. 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 however, no power is applied to the slip rings. The speed regulation is poor with respect to changing torque loads. With a liquid rheostat, or a static secondary speed control, the wound rotor is an important alternative drive where limited range adjustable speed is required. You should also make a dc measurement of stator winding linetoline resistance using a dmm. Speed control of wound rotor induction motors by ac regulator based optimum voltage control abstract. In this type of three phase induction motor the rotor is wound for the same number of poles as that of stator but it has less. The speed torque curves of the wound rotor induction motor. Squirrel cage induction motor is used in lathes, drilling machine, fan, blower printing machines etc.
The three phase induction motor is the most widely used electrical motor. In the electrical model, the voltage, v, and the slip, s, determine the rotor current. A wound rotor induction motor has a stator like the squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. This speed control technique is only useful over a range of 50% to 100% of full speed. Rotor induction motor at noload and fullload to observe speed control using an. Let us call this procedure additional voltage to the rotor. Why the rotor speed is less than the synchronous speed. Speed control at the rotor side we can change the speed at the rotor by,by adding some external resistance in the rotor circuitby cascade connection of the motor. Wound rotor induction motors ac motors electronics. Speed control of induction motor detailed explanation. Woundrotor induction motors are generally used for high torque and adjustable speed conditions. 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 wound rotor induction motor has some distinct application advantages. Threephase motors wound for 50 hz can also be connected. Speed control of wound rotor induction motor using rotor resistance control aim to use variable resistance in the rotor circuit to control wound rotor induction motor speed theory polyphase induction motors are mainly of two types by construction, squirrel cage and wound rotor with sliprings. Performance enhancement of wound rotor induction motor by vsi. Pdf torque and speed control of wound rotor induction. A wound rotor induction motor has a stator like a squirrel cage induction. Speed regulation of induction motors with wound rotor. The summation of all torques acting on the motor shaft comprises the mechanical model. These motors are having the difference in rotor construction. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting. Improving motor and drive system performance esr motor systems. Motor analysis block diagram induction motor starting can be analyzed using electrical, mechanical, and thermal models which interact as diagrammed in figure 1. Induction motors are the most widely used motors for appliances, industrial control, and automation. Instead of a series of rotor bars, a set of insulated rotor coils is.
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