Torque equation of three phase induction motor pdf

What are the torqueslip characteristics of a 3phase. Sep 07, 2017 maximum torque three phase induction motor electrical capsule. Find the starting current of 10 hp, three phase 220 v a class motor. Since the rotor currents cannot be measured with cage motors, this current is replaced by an equivalent quantity described in a rotating coordinate system called d,q.

The induction motor block implements a three phase induction motor. The frame provides the structural support for all other motor components. The singlephase induction motor is more subtle and less efficient. The torque is produced in induction relays due to the interaction of one alternating flux with eddy currents induced in the rotor by another alternating flux.

Design a is a generalpurpose design used for industrial motors. 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. Torque equation of three phase induction motor electrical4u. This curve is called the torquespeed characteristic curve. So by substituting s r 2 x 2 in full load torque expression, we get the maximum torque expression. An induction mot or o r asynchronous mot or is an ac ele ctric mo tor in which the electric current in the rotor needed to produce to rque is obtained by electr omagnetic induc tion from the magnetic field of the stator winding. Maximum torque condition in the equation of torque, so, for torque to be maximum, 10. The threephase induction motor is the easiest motor of this type to understand so these notes start with that type. Torqueslip characteristics in three phase induction motor. If are given and the time function is also given, then the above equations unambiguously define the motor currents. In these relays, a metallic disc is allowed to rotate between the two electromagnets. Speed torque characteristics of 3 phase induction motor duration.

The present invention relates to a three phase induction motor and, more particularly, to a three phase induction motor having a relatively low capacity, e. The torque produced in the induction motor depends on the following factors. Torquespeed characteristics of three phase squirrel cage. Its starting torque is somewhat inferior to that of a d. The induction type relays are also called magnitude relays. In fact, an induction motor can be treated as a rotating transformer i. Physical layout of induction motor in an induction motor induction refers the field in the rotor is induced by the stator currents and asynchronous refers that the rotor speed is not equal to the stator speed.

We can derive an equation from the equivalent circuit that allows the calculation of the torque for a given value of slip. Torque equation of an induction motor starting torque circuit globe. More expensive than three phase motors of the same output. An ind u ction motors rotor can be either wound type or squirrelcage type. The threephase induction motor is the extensively used for various kinds of industrial drives. Torque formula for induction motor your electrical guide. This torque is differs from the torque actually available at the terminals by the friction and windage torque in the induction motor. The part of rotating magnetic field which reacts with the rotor and is responsible to produce induced e. Torque equation of 3 phase induction motor duration. One singlephase wattmeter plus miscellaneous apparatus as needed. The torque t is developed in a three phase induction motor depends upon the following three factors.

The torque produced by three phase induction motor depends upon the following three factors. Jul 11, 2019 so, the equation of starting torque is easily obtained by simply putting the value of s 1 in the equation of torque of the three phase induction motor, the starting torque is also known as standstill torque. Its main function is to support the stator core and the field winding. The part of rotating magnetic field which reacts with the rotor. Jul 11, 2019 torque slip characteristics of three phase induction motor the torque slip curve for an induction motor gives us the information about the variation of torque with the slip. A three phase induction motor runs on a three phase ac supply. An induc t ion motor can therefore be made without electrical connections t o the rot o r. So putting s 1 in the torque equation we can write expression for the starting torque t st as. The block uses the threephase input voltages to regulate the individual phase currents, allowing control of the motor torque or speed. The 3phase set of currents, each of equal magnitude and with a phase difference of 120 o, flow in the stator windings and generate a rotating field will constant magnitude. The 3phase set of currents, each of equal magnitude and with a phase. The single phase induction motor is more subtle and less efficient. From the equation 10, it is clear that by changing the starting torque can be controlled. This is the principle used in case of slip induction motor to control the starting torque t st.

A threephase stator similar to that of an induction motor. Construction an induction motor consists essentially of two main parts. We only have three regions or three cases to illustrate and predict variation and they are. In twopole singlephase motors, the torque goes to zero at 100% slip zero speed, so these require alterations to the stator such as shadedpoles to provide starting torque. This design exhibits normal torques and fullload slip of approximately 3 percent and can be used for many types of industrial. The block uses the three phase input voltages to regulate the individual phase currents, allowing control of the motor torque or speed. The rotor of the squirrel cage three phase induction motor is cylindrical in shape and have slots on its periphery. The three phase induction motor is the easiest motor of this type to understand so these notes start with that type. So, the equation of starting torque is easily obtained by simply putting the value of s 1 in the equation of torque of the three phase induction motor, the starting torque is also known as standstill torque. The national electrical manufacturers association nema provides design letters to indicate the torque, slip, and starting characteristics of threephase induction motors they are as follows. The basic idea of an electric motor is to generate two magnetic fields. There are three basic types of small induction motors. In the equation of torque, the rotor resistance, rotor inductive reactance and. Torqueslip characteristics in three phase induction motor as the induction motor is located from no load to full load, its speed decreases hence slip increases.

A wound rotor rotating field which has the same number of poles as the. The synchronous speed of the motor is given by equation 1. Maximum torque condition for three phase induction motor. The two fluxes have the same frequency but are displaced in time and space. The part of rotating magnetic field which reacts with rotor and is responsible to. By default, the block sets the simulation type parameter to continuous to use a continuous sample time during simulation. A single phase induction motor requires separate starting circuitry to provide a rotating field to. Jan 11, 2018 where s start rated hp of the motor code factor code factor is a number which is reserved for class for example, all motors of class a have a fixed code factor which should be multiplied with rated hp in the above equation.

Lecture 6 three phase induction motors cairo university. Torque equation of an induction motor the developed torque or induced torque equation in a machine is defined as the torque generated by the electric to mechanical power conversion. The slip is defined as the ratio of the difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. Starting torque is the torque produced by induction motor when it is started. How an induction motor works by equation s and physics. The maximum torque is denoted by t m and occurs at s r 2 x 2. Maximum torque three phase induction motor electrical capsule. Dynamic simulation of a threephase induction motor using. Stator frame it is the outer most part of the three phase induction motor.

The stator carries a distributed winding in the slots cut around the inner periphery. The electric torque of an ac induction motor can be described by the interaction between the rotor currents and the flux wave resulting from the stator current induction. Record all nameplate information for the induction motor. Torque of a three phase induction motor is proportional to flux per stator pole, rotor current and the power factor of the rotor. Maximum torque three phase induction motor electrical. As shown in equation, the developed torque depends on the air gap power and synchronous speed. Induction motor torque, torque equation, starting torque, torque at synchronous speed, condition for maximum torque is explained in this. The first industrial motors of this type were constructed at the end of the nineteenth century and soon gained the favor of users who appreciated their raggedness, simplicity and relatively low manufacturing cost compared to dc commutator motors. So, the equation of starting torque is easily obtained by simply putting the value of s 1 in the equation of torque of the three phase induction motor, maximum torque condition for three phase induction motor. Dec 17, 2018 the speed of the induction motor is characterized by the term known as the slip. The magnetic field in the air gap from the voltage applied to the stator. Torque slip characteristics of induction motor full guide. Ss 120 x f p 120 x 60 8 900 rpm rotor speed motor slip is known, equation 2.

Generally three phase induction motor is treated as rotating transformer. Torque equation of 3 phase induction motor youtube. Equation of starting torque of three phase induction motor. Torque equation of three phase induction motor electrical. The coils of the electromagnets are energised with the help of alternating currents.

Figure 1 characteristic curves of an induction motor. The motoring region of the induction machine torquespeed curve is the region of greatest interest. Torque equation of an induction motor starting torque. If is not known or not given and must be calculated from the torque or motion equation, then the above equation system becomes nonlinear. Magnitude of rotor current in motor running condition i2, the power factor of rotor of. The value of slip which corresponds to maximum torque is denoted by s m. Starting torque is nothing but the torque produced by an induction motor as start. Torque equation of threephase induction motor electrical article.

That is why such motors are known as induction motors. The synchronous speed is independent of loading condition and it is constant. The operation range of an induction motor can be divided into three regions according to the output torque capability as constant torque region. Ac induction motors are also the most common motors used in main powered home appliances.

Three phase induction motor performance electrical academia. Torque of a three phase induction motor is proportional to flux per stator pole, rotor current and the power factor of the rotorthe torque. The torque is also known as electromagnetic torque. Therefore maximum torque formula for induction motor is as follows. Variable voltage variable frequency vf control theory an induction motor compared to a dc motor has some major advantages such as. They form a linear differential equation system with time dependent coefficients. How an induction motor works by equations and physics. The frame must be made up of the rigid material that can absorb vibration as well as noise in the induction motor. Using the induction machine power and torque equations it is possible to. Induction motor aim to obtain the torquespeed characteristics tn r of a three phase squirrel cage induction motor using 1. Synchronous motors synchronous motors are threephase ac motors which run at synchronous speed, synchronous motors have the following characteristics. You should also make a dc measurement of stator winding linetoline resistance using a dmm.

The power produced by the motor depends on the speed of the motor and is. The starting torque is obtained by putting s 1 in equation hence, it is clear from the above equation that the starting torque is proportional to the square of the stator applied voltage. Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. More expensive than threephase motors of the same output. Multiple solutions of the above equation for torque at different slips can be made simpler by simplifying the equivalent circuit model. This developed torque in the motor differs from the actual torque available at the terminals of the motor, which is almost equal to the friction and windage. The rotor will constantly be turning to align its magnetic field with that of the stator field. Comparing both the equations, we get, constant k 3 2. A 3 phase, 400 v, 50 hz, 4 pole induction motor has star connected stator winding.

A 480v, 60 hz, 6pole, threephase, deltaconnected induction motor has the. Review of modeling and dynamic analysis of three phase. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. Torqueslip characteristics of three phase induction motor dont have big difference than of the main induction motor. Now, the electrical power generated in the rotor is given by the equation shown below. Torque equation of threephase induction motor electrical. These relays work on the principle of the induction motor or an energy meter. Full load torque formula for induction motor is as follows starting torque formula for induction motor the starting torque of a motor is that torque which is produce by it at start. The change in r 2 at start is possible in case of slip ring induction motor only. Torque equation the torque produced by three phase induction motor depends upon the following three factors.

The torque is the twisting force that makes the motor running and the torque is active from 0% to 100% operating speed. 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. Single phase induction motor is very simple and robust in construction. May 20, 2018 torque slip characteristics of three phase induction motor.

The main objective of this paper is to simulate the induction motor model in matlab simulink and study the effect of speed, torque, stator and rotor currents on three. Torque slip characteristics of induction motor electrical4u. Figure 1 showed a plot of induction motor torque vs speed from zero to synchronous speed. In twopole single phase motors, the torque goes to zero at 100% slip zero speed, so these require alterations to the stator such as shadedpoles to provide starting torque. The three phase induction motors are simple in construction, rugged, low cost and easy to maintain. Slip is the ratio between the slip speed and synchronous speed. The induction motor block implements a threephase induction motor. One single phase wattmeter plus miscellaneous apparatus as needed.