Pengaruh Harmonik Akibat Pengoperasian Motor Induksi Tiga Fasa Pada Sistem Tenaga Satu Fasa

Slip power recovery scheme is widely used for controlling the speed of a three-phase induction motor, but this method can also be used for increasing the efficiency of an induction motor. Here, a three-phase induction motor has been designed using vector-controlled induction motor drive and then the controlled strategy is introduced in this induction motor. The control strategy is based on feeding the slip power back to the rotor of a slip ring induction motor. The efficiency and torque of a three-phase induction motor depend upon the slip of the motor. This controller monitors the speed of the motor from no load to full load and takes the appropriate control action to maintain the speed of the motor. After implementation of this control strategy, it has been seen that the induction motor is trying to maintain the no load speed and as a result, the power output of the motor has been increased considerably.

The airgap flux density, and torque of a double three-phase induction motor using a special phase current waveform are investigated in this paper. The special current waveform proposed by the authors comprises of field and torque current components. The aim of using the special current waveform is to realize torque and field control of the motor separately, instead of using the conventional d-q transformation. Three methods are used to verify the flux density and torque of the motor namely conventional analytical calculation, finite element calculation and practical measurements. The practical measurements include field and torque control by means of two full-bridge converters under DSP current control. The results obtained from these methods show good agreement. The results furthermore show that the field and torque of the induction motor can be controlled effectively and in a very simple way by using the special current waveform.

Introduction. Single-phase power supply of induction motors is used in public utilities, in microclimate control systems for remote agricultural consumers, in water supply and pipeline transport systems, etc. In practice, there is the use of induction motors with three-phase stator winding in the conditions of single-phase power supply. Starting and operating capacitors are used to enable their operation when powered by a single-phase network. Problem. There are many fairly accurate methods for calculating the characteristics of an induction motor in asymmetric, including single-phase, modes of operation, but they are based on differential equations, which does not allow to obtain analytical expressions for preliminary analysis and synthesis of such systems. Goal. The purpose of this article is to develop the analytical method of definition of electromagnetic torque and energy losses of voltage-regulated three-phase induction motors working according to the scheme of single-phase inclusion with the phase-shifting capacitor. Methodology. The method is based on the theory of symmetric components and analysis of replacement schemes of induction machine in motor and generator modes. Results. The analysis of the obtained data shows that at a constant value of the phase-shifting capacitor capacity induction motor working according to the scheme of single-phase inclusion has a minimum of losses at one value of slip at different values of supply voltage. Therefore, if you keep this slip constant when the load changes, you can achieve a mode of minimizing losses at a constant value of the capacity, optimal for this slip. This shows that the thyristor voltage regulator can be used as an energy-saving element under variable load, while the capacitance of the phase-shifting capacitor can remain constant when changing the load in a wide range provided that this slip is stabilized. Originality. The developed method allows to obtain analytical expressions for comparative analysis of electromagnetic torque and energy losses of three-phase induction motors powered by a single-phase network at different values of the capacity of the phase-shifting capacitor, supply voltage for different variants of schemes for including three-phase induction motors in a single-phase network. Practical value. Based on the developed analytical method, the optimal parameters of phase-shifting capacitors and rational schemes for including three-phase induction motors in a single-phase network can be determined.

It is well known that the harmonic torques in squirrel cage induction motors are caused by the space harmonic waves in air-gap flux distribution. The soft ferrite magnetic wedges inserted into the stator slot openings reduce the ripple of air-gap permeance. Therefore, this wedges reduce the magnitude of harmonic torques. A trial was performed on prevention of harmonic torques in squirrel cage induction motors, by inserting a soft ferrite magnetic wedges into its stator slot openings. Results obtained were as follows; (1) The soft ferrite magnetic wedges made it possible to decrease by about 40% the 17th and 19th asynchronous torques. (2) The magnitude of 17th and 19th asynchronous torque on the induction motor with the soft ferrite magnetic wedges and the unskewed rotor is approximately equivalent to that on the induction motor with the rotor skewed through 0.4 stator slot pitch. (3) The soft ferrite magnetic wedges were incapable of decreasing the 5th asynchronous and synchronous torque. The authors suggest that the utilization of soft ferrite magnetic wedges will become important to prevent the harmonic torques in induction motors.

From the late nineteenth century to the present, Tesla's motor has been advantageously used in many applications where the torque capabilities, acceleration characteristics, power density, and high degree of reliability are indispensable. Nevertheless, in the design of high performance electrical drives, the choice of DC motor was preferable, since its torque and flux are controlled independently through two separate terminals. To match this suitable feature of a DC motor in servo applications, the concept of vector control was developed to enable decoupled control of the flux and torque of the induction motor; thus, Tesla's motor may enable control characteristics of a DC motor. In this paper, it is shown how Tesla's induction motor can be applied in the design of digitally controlled speed servo drive in the presence of immeasurable arbitrary torque disturbances. For rejection of effects of torque disturbance on the steady-state value of motor speed the principle of absorption is applied in the design of a disturbance estimator within the control portion of the system controlling structure.

Three-phase induction motors are still dominant operators for many modern industrial applications. Many control methods implemented to control the speed and torque of induction motors in applications such as electric vehicles. The main objective of this paper is to compare the performance of a three-phase induction motor controlled by using a novel Direct Torque Control (DTC) method and Indirect Field Oriented Control (IFOC) method. MATLAB/SIMULINK program is used to make a complete computer model of the induction motor. Then, the speed of the computer model is controlled using a novel DTC and IFOC respectively. It is concluded that the novel DTC is suitable for constant reference speed applications, and IFOC method is suitable for applications that required variable reference speed.

Due to sensor limitations in some applications, induction motors state estimators are widely used in industries. One of the most powerful tools available for estimation is the Kalman filter. In this paper, unscented Kalman filter (UKF) and extended Kalman filter (EKF) is used to estimate the speed and torque of an induction motor. In the UKF algorithm, three types of unscented transformation (UT): basic, general and spherical types are presented and compared. It will be shown that the spherical UKF presents good estimation performance. Speed and torque Estimation approach is applied at both steady state conditions and at the time of sudden and rapid change in the motor input voltage. It will be shown that, EKF cannot trace the motor speed at the time of a large disturbance. Finally, experimental validation is presented to show the effectiveness of UKF for continuous estimation of torque and speed of induction motors.

AC motors, especially the squirrel cage induction motors have the advantages of simple structure, good reliability and low cost. They are more suitable to be used as electrical dynamometers to provide dynamic load for bench test systems. But, the speed and torque of induction motors are not easy to be controlled accurately. In this work, an electrical dynamometer based on the induction motor is proposed. In order to get better control performance of torque and speed of induction motor, an improved direct torque control method (DTC) is also developed based on the space vector modulation (SVM) technique. The performance of the proposed dynamometer system is validated in the Matlab/Simulink platform. The simulation results show that the new dynamometer has good torque and stator flux response. And the torque and stator current ripples of it are reduced significantly compared with using the conventional DTC method.

Most of the researches for adjustable speed drive focused on voltage amplitude control. However, its only control speed in the constraint limits. Adjustable frequency drives have not been widely used with single-phase induction motors. The scalar control law used for many three-phase inductions motor cannot be used in all operating regimes of the single-phase motor. Calculations show that the slip of the single-phase induction motor is not constant with changes in frequency at a constant load torque. A constant 'volts per hertz' law is found to give approximate rated torque over a portion of the upper speed range, but the maximum available torque decays rapidly below 50% of the base frequency. This paper aims to study the behavior of the single phase induction motor's torque and slip characteristic under variable frequency operation. By holding the level of magnetization constant, a control law can be achieved. This method is implemented for the practical adjustable speed of the single-phase induction motor. If time permit, the final draft paper includes the practical experimental results to compare the simulation results in order to achieve satisfactory agreement for torque and slip behavior of single-phase induction motors driven from variable frequency supplies

Induction motor is widely used due to advantages in terms of performance, size, maintenance and efficiency compared to dc motor. Induction motor is either Scalar Controlled or Vector Controlled. Magnitude of voltage and frequency is controlled in scalar control and drive has better performance under steady state. The coupling effect of flux and torque makes the drive sluggish. In vector control of induction motor drive, the flux and torque producing currents are independent of each other, making the transient response of the system better. Direct and indirect vector control is classified depending upon how the magnitude and position of the flux vector are determined. The specifications or parameters of the induction motor have least effect on the performance of the induction motor drive. This is because the measured or estimated flux is processed in the feedback loop for speed control operation of the drive. However, use of flux sensor within the machine which makes the drive uneconomical. In indirect vector control, rotor position signals are used for instantaneous rotor flux magnitude and position estimation. Motor parameters, used for estimation of flux vector vary with frequency, magnetic saturation and temperature. Vector Control is achieved using any of the rotating flux vectors in the induction motor. The vector control must have independent control of flux and torque, rotor flux orientation provides the independent control or natural decoupling. This decoupling leads to improved stability and enhanced dynamic response. Sensitivity is the problem associated with terminal quantities based flux observers. Research has been carried out to overcome the aforementioned problems by implementing accurate estimation of rotor flux. The selection criterion for the control principle depends upon the cost, accuracy, reliability and stability requirements. The uncertainties in the system parameters give way to a more robust and dynamic controller. The sliding mode control is one of the popular control techniques used to handle the uncertain system parameters, model uncertainties and external load variations which exist in induction motor drives. The induction motors used in traction require low speeds only during starting and low speed operations. The power output of the motor can be maximized by limiting the current drawn by the motor to rated value and lowering the reference voltage. The sliding mode control offers a robust tracking of a given speed demand when subjected to disturbances from both input and output side. This gives better performance compared to other techniques. Control Algorithm: Sliding Mode Controlled three-phase induction motor is shown in Fig. 1. It consists of three-phase rectifier converting the ac grid voltage into dc voltage which forms dc bus for PWM Inverter. Sliding mode algorithm is used for controlling the inverter which powers the three-phase induction motor.The aim of the control algorithm is to control the inverter voltage so that the induction motor tracks the desired speed. Two-line voltages and phase currents are sensed into the controller. These line quantities are converted to α-β components by the conventional 3-phase to 2-phase transformation. Synchronous speed is determined using frequency estimator and then estimated mechanical speed is compared with speed reference to give speed error. This error forms the input for the Sliding Mode control. In addition to this, torque current reference and actual torque current component are compared to give the voltage reference Vds. The voltages are converted to Va, Vb and Vc using the reverse transformation. By conventional Sine-triangle comparison, switching pulses are generated. SIMULATION RESULTS: Motor response with Indirect Field Oriented Control is as shown in Fig. 2. It can be observed that the motor accelerates at the starting with maximum torque. As the motor reaches the desired speed, the generated torque becomes minimum. At t = 0.5 sec, load torque is applied on the motor resulting in the transient shown.Fig. 2 - Electromagnetic torque and Speed of the three phase induction motor with IFOC algorithm. For the same transient conditions, motor is controlled using Sliding Mode control algorithm. The results are shwon in Fig. 3. The motor torque and speed response shows lower ripple which which validates the robustness of the algorithm.Fig. 3 - Electromagnetic torque and speed of the three phase induction motor with Sliding Mode Control.

The conventional method of a single phase induction motor windings design usually constructed the main and auxiliary windings in both slot. So, there was a complicated winding design if that compare to the three-phase induction motor. Because of that, this study was aimed to design a new windings design of a single phase induction motor that construction like a three-phase induction motor. This study was focused to design a 24 slot capacitor-start capacitor-run induction motor. The windings in the motor are divided in 3 group like a three-phase induction motor. The two windings act as a main windings and the other winding act as auxiliary winding. The current rating of the winding of the proposed single-phase induction motor was 2.74A. The performances of the proposed method were compared with the performances of a three-phase induction motor that had the same current rating. The motor used as a comparator was a three-phase induction of 380/220V, 2.74/4.7A, Y/Δ, cage rotor, 4 poles, 1.5 HP, 1400 RPM, 50Hz. The result of this study showed that the proposed design of single phase induction motor could be operated with better performances than the three-phase comparator induction motor’s.

Induction motors has wide application in industries because of its rugged, easy operation and requires less maintenance characteristics. Besides the fact that they are reliable, they are exposed to different types of faults from which Unbalanced voltage supply is one such external fault. This fault can bring about issues like excessive warming due to huge amount of losses, over-voltages, mechanical oscillations, audile noise and so on. Here, the impact of unbalanced voltage supply on the induction motor performance is studied. The analysis has been done to find the unbalanced voltage effect on the induction motor current and torque. For this, 16 different voltage unbalance cases have been picked with 8 different voltage unbalance type and 2 different voltage unbalance factor (VUF). Matlab Simulink is the tool used here for performing the experiment and its analysis.

This paper presents a platform for illustrating the speed- torque characteristics of a vector controlled three-phase induction motor. The methodology is based on acquiring the estimated torque and actual speed of a three-phase induction motor and plotting the speed-torque characteristic in real time. The platform contains a graphic interface to drive the motor and acquire the data, an induction motor, an AC drive, a communication protocol between the computer and the AC drive, and a loading system for the motor based on the claw pole alternator. LabVIEW has been used for designing the control interface. This control interface includes speed adjustment, stop command, direction of rotation, and drawing the speed-torque characteristic in real time to make the student able to notice the performance of the induction motor in the vector control mode.

Electrical variable speed drives (VSDs) are the most widely used power-electronics-based equipment in the industry that controls the performance (speed and torque) of AC induction motors (IMs). One of the main tasks of the VSDs is soft starting the IM. VSDs are usually programmed to start the IM from standstill (zero speed). In many industrial applications, due to high inertia of load or external forces such as wind, the IM may spin while the drive is in standby or off state. In such cases, high electrical and mechanical shock will be applied to the IM (and VSD) if the start command is sent. However, in cases that the IM rotation speed and direction is estimated, the VSD can control the IM from the estimated speed without any stress. The starting method without any sensor (or encoder) is called sensorless flying start (SFS). In this paper, a new SFS method for VSDs is introduced and verified in MATLAB/SIMULINK environment.

Neuro-Fuzzy Approach to Estimate the Torque in Three-Phase Induction Motors with Unbalanced Power