Jun 05, 2018 main motor stator terminal is connected to the supply main and the slip power of main motor is fed to the stator terminals of auxiliary induction motor through slip ring as shown in figure below. Keywords cycloconverter, split phase induction motor i. Voltagefrequency vf control of induction motor drives. This is the constant torque region where vf control can be applied, with low frequency voltage boosting. This is why using vfd to control an induction motor was a good idea.
Software platform namely siemens ladder logic programming s7200 was comprehended, analyzed and implemented. Methods of speed control of induction motor electrical. Braking of induction motor with the technique of discrete. Three phase induction motor was fully automated using a plc. The control is more difficult but this is solved by the constant improvement of the speed and calculating power of modern processors. Induction motor parameters locked rotor test the locked rotor. While there are different methods for control, variable voltage variable frequency vvvf or vf is the most common method of speed control in open loop. This speed control method is known as volts per hz. Speed control of three phase induction motor by variable frequency drive 1madivalappa. Speed control of three phase induction motor drive using. When ratio is constant, constant air gap flux is obtained. Variable frequency drive for induction motor elprocus. In this way, the slip power of main motor is fed to the auxiliary induction motor at a frequency of f 2 s 1 f 1 let us now assume that p 1, p 2 and s 1, s 2 be the number of poles and slips respectively.
Scalar control of induction motor drives using dspace ds1104. Any variable frequency drive or vfd incorporates following three stages for controlling a three phase induction motor rectifier stage. For our knowledge, in textbooks and literature, the unique description of designing slipregulator using analytical approach was described in. A modified approach to induction motor stator voltage and. Thyristorized soft starters are being used as induction motor starters in fan or pump drives, etc, the principle of which is based on the control of variable voltage and constant frequency. The control used must be such that the air gap flux is constant at all operating points. Furthermore, the measurements of slip compensation parameter change influence on motor speed and motor load dependence are performed, as well as measurements of power factor correction attained by frequency converter. Speed control of induction motor by variable frequency control.
Speed and frequency control of ac induction motor using. However, asynchronous motors do not inherently have the capability of variable speed operation. The most popular type is the 3phase, squirrelcage ac induction motor. Variable frequency drive or vfd is the way that enables controlling of the speed of induction motor by applying varying frequency of ac supply voltage. Nov 30, 2016 speed of a 3 phase induction motor can be controlled by these methods. Variable voltage variable frequency control of threephase induction motor in closed loop is the significant feature of the thesis work. Oct 01, 2016 the speed control of three phase induction motor from stator side are further classified as. 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. They can be used in control of motors used in conveyors and other machinery. The parameters of equivalent circuit of induction machines are crucial when considering advanced control techniques i. Typically in centrifugal pump and fan applications perhaps as much as 90% of the vfd applications out. Jan 09, 2017 speed control methods of induction motor. Speed control of induction motor using cycloconverter.
Block diagram of variable frequency control of induction motor drive scheme is shown in fig. If the triac circuit is operated in a motor control mode where it conducts for full line cycles, but not every line cycle. Firstly threephase induction motor drive system is simulated in various modes using matlabxilinx, then finally closed loop control of induction motor is. 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. Two induction motors are cascaded for the purpose of speed control. In the beginning frequency converter control of induction motor is explained. V and f are voltage and frequency commands for vfvs. Analysis of variable frequency three phase induction motor drive. We already know that if we change the frequency of supply then we can easily change the speed of induction motor by the. A variable voltage, variable frequency drive is capable of operating over a wide speed range. In this method of speed control of three phase induction motor rheostat is added in the stator circuit due to this voltage gets dropped. Induction motor is now called the racehorse of the industry 1. In this post let us see what are the various methods to control the speed of induction motor.
There are three distinct operating modes, illustrated in the diagrams below. Lets talk about two different load one is high load and other low load. The synchronous speed of an induction motor is given by the relation shown below. The present work was motivated to develop a scheme to monitor and control by using plc. The motor is fed from a variable frequency variable voltage source vfvs. As we already know that the torque developed is proportional to the square of the supply voltage and the slip at the maximum torque is independent of the supply voltage. The system was investigated, tested and simulation results are shown and discussed. The main motor has 6 poles and the other motor has 4 poles. Speed control of induction motor using variable frequency. Dec 17, 2019 any variable frequency drive or vfd incorporates following three stages for controlling a three phase induction motor rectifier stage.
Speed control of 3 induction motor using volts hertz control. Scalar control is the term used to describe a simpler form of motor control, using nonvectorcontrolled drive schemes. You should also make a dc measurement of stator winding linetoline resistance using a dmm. Induction motor using volts hertz control method 233 frequency. This paper presents design and analysis of a three phase induction motor drive using igbt.
Theres not a right answer to this question it depends too much on the application, the driven motor and the particular drive youre using. Variable frequency control of induction motor drive. Dec 17, 2019 therefore by changing the number of poles we can easily change the speed of three phase induction motor. We know that t he speed of the induction motor is given by, from the above equation, the speed of the motor can be controlled by changing supply frequency and by changing number of poles in the stator. Speed control of three phase induction motor electrical4u. The name itself suggests that vfd uses voltage and frequency to control the speed of induction motor. The amount of slip depends on the input power, the applied load, and the characteristics of the specific motor. It is a 16 bit highperformance digital signal controller dsc. Optimal control of induction motor using high performance frequency converter jerkovic vedrana, spoljaric zeljko and valter zdravko faculty of electrical engineering department of electromechanical engineering, osijek, croatia, email. Cycloconverters are used in very large variable frequency drives with ratings from few.
By controlling the output ac frequency, it is possible to drive the motor at different speeds based on the requirements. Depending on the motor, there can be significant torque pulsations when a singlephase induction motor is run at low speeds. Speed control of induction motor using variable frequency drive. The speed control of induction motor is done at the cost of decrease in efficiency and low electrical power factor. The system may include transformers for high voltage system. Hence, the synchronous speed changes with change in supply frequency. At low load motor is delivering the load with some current and thereby torque is maintained.
Then for the main motor, synchronous speed is 120f 1. To simulate an electric vehicle drive with an induction motor, a frequency converter is needed. Induction motor control is complex due to its nonlinear characteristics. The speed of an induction motor can be easily controlled by varying the frequency of the 3phase supply. Aug 08, 2014 induction motor is constant speed motor at a particular frequency and consumes almost same power irrespective of load demand. The complete control circuitry depends on only one parameter i. Singlephase motors can also be used, but they have limited performance in the lowspeed range. Speed and frequency control of ac induction motor using variable frequency drive 1syed usama hassan, 2hafiz bilal akram department of electrical engineering, institute of space technology, islamabad, pakistan bilalakram. The threephase motor gives good torque performance at all operating speeds. The most common ways, to manually determine induction motor.
Why use variable frequency drive for 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. Investigation in induction motor starting and speed. In this way, the slip power of main motor is fed to the auxiliary induction motor at a frequency of f 2 s 1 f 1. On the input side, voltage doublers are used and on the output side an hbridge, or 2phase inverter, is used as shown in figure 2.
Stator voltage control of an induction motor circuit globe. Svpwm algorithm for induction motor control and to improve the efficiency of vfd drive. Nov 26, 2015 this is a brief discussion about variable frequency drive of an induction motor. Depending on the motor, there can be significant torque pulsations when a singlephase induction motor is.
Variable frequency control vf of induction motor 1. The inverter used to supply an variable frequency induction motor must be capable of providing a variable voltage, variable frequency supply. The application serves as an example of ac induction vector control drive design using a motorola dsp with sdk support. Stator voltage control is a method used to control the speed of an induction motor. 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. An984, an introduction to ac induction motor control using. Variable frequency control vf of induction motor 1 youtube. Some say that the speed can even be reduced by using a triac while others say that a resistor in series can destroy an induction motor. Design and control of the induction motor propulsion of an electric vehicle b. A three phase induction motor is basically a constant speed motor so its somewhat difficult to control its speed. For variable voltage variable frequency vvvf drives, there is a need to control the fundamental voltage of the inverter if its frequency and therefore the frequency of the induction motor. Induction motor is constant speed motor at a particular frequency and consumes almost same power irrespective of load demand.
Around rated frequency it is valid that stator voltage. An843, speed control of 3phase induction motor using. Speed control of induction motor by variable frequency control variable frequency control is a method which is used to control the speed of an induction motor. The rotor is unblocked and allowed to run unloaded at rated voltage and rated frequency. The speed control of three phase induction motor from stator side are further classified as. Ac drive vfd is capable of adjusting both voltage and speed of an induction motor, synchronous motor and etc. A fullwave power diode based solidstate rectifier converts threephase 50 hz power from a standard 220, 440 or higher utility supply to either fixed or adjustable dc voltage. Speed control of three phase induction motor by variable.
There are several methods for the speed control of induction motor. Accidentally these are also uncertain parameters when the machine is released from production. Speed control of variable frequency induction motor. Introduction speed control of induction motor is necessary in industrial applications. Variable voltage variable frequency speed control of. Various methods of speed control in three phase induction. When motoring the rotor frequency is always lower than the stator frequency. Three phase induction motor drive using igbts and constant v. Speed of a 3 phase induction motor can be controlled by these methods. Vfd variable frequency drive referred to variety of names, such as adjustable speed drives, adjustable frequency drives or variable. It is widely used in industry due to low cost and rugged construction. The speed of a three phase induction motor can be varied by varying the supply voltage. It gives the possibility to use it to show people about the control of an induction motor and the step towards electric cars is easily made.
The speed torque curves of the motor for this type of control are shown in fig. Firstly threephase induction motor drive system is simulated in various modes using matlabxilinx, then. Aspalli department of electrical and electronics engineering, pdace, gulbarga, karnataka, india abstract there are several terms used to describe devices that. This is a brief discussion about variable frequency drive of an induction motor. Variable speed drive of single phase induction motor using. The synchronous speed and therefore, the speed of the motor can be controlled by varying the supply frequency. What is the range of frequency in vf speed control of. Methods of speed control of induction motor electrical concepts. Analysis of variable frequency three phase induction motor. Asynchronous motors are the most widely used electrical motors due to their reliability, low cost, ruggedness and robustness. A vfd variable frequency drive is a controller used to control and monitor parameters of induction motor such as speed.
A three phase induction motor is basically a constant speed motor. Various induction motor speed control methods advantages. Determination of inductionmotor parameters at noload, the speed is very close to synchronous speed the slip is 0, causing the current in r2s to be very small, and will be ignored i the calculations. It also illustrates the usage of dedicated motor control libraries that are included in the sdk. Control of induction motors by using programmable logic. When the motor is conducting current, its voltage and frequency are matched and the motor produces normal operating torque. The previous control strategies good steadystate but poor.
The difference between these two frequencies is called the slip. This combination of motor and converter led to many possible experiments. Actual speed of an induction motor is given as n ns 1 s. Variable frequency drives, induction motor, speed control, pulse width modulated inverter. Design and control of the induction motor propulsion of an. Calculate the possible speed that can be obtained if the set is run on asupply of 50 hz frequency. Record all nameplate information for the induction motor. Before discussing the methods to control the speed of three phase induction motor one should know the basic formulas of speed and torque of three phase. Speed control of 3 induction motor using volts hertz. Due to this reason, earlier dc motors were applied in most of the electrical drives. But the recent developments in speed control methods of the asynchronous motor have led.
An843, speed control of 3phase induction motor using pic18 mcus. In case of three phase induction motor torque produced is given by t. Out of the several methods of speed control of an induction such as pole changing, frequency variation, variable rotor resistance, variable stator voltage, constant vf control, slip recovery. Vectorcontrolled induction motor drives the previous control strategies good steadystate but poor dynamic response oscillation resulted from the air gap flux vector control fieldoriented control is related to the phasor control of the rotor flux. Research about the control of electric motors is by that become a hot topic. How to control the speed of 3 phase induction motor quora. Application circuit to control the speed of single phase induction motor the approach is relatively easy as far as the power circuit and control circuit are concerned. It may be used where, the induction motor is supplied by a dedicated generator so that frequency can be easily varied by changing the speed of prime mover. Voltage frequency vf control of induction motor drives. According to equation 3 air gap flux is directly proportional to vsf. Optimal control of induction motor using high performance. An introduction there are various methods for the speed control of an induction motor. It has been more than a century since the principle of the operation of induction motors was discovered.