A new induction motor drive based on the flux vector acceleration method

A novel control strategy for the induction motor drive, based on the field acceleration method, is presented. The torque is controlled through variations of the stator flux angular velocity. The stator flux is controlled by using a feedforward control scheme, with the stator flux reference vector adjusted so as to obtain the fixed rotor flux amplitude. The applied controller assures a fast torque response, low torque ripple in the steady state, and drive operation with a constant switching frequency. The algorithm includes the improved stator and rotor flux estimation that guarantees the stable drive operation in all operating conditions, even at low speeds. The experimental tests verify the performance of the proposed algorithm, proving that good behavior of the drive is achieved in the transient and steady-state operating conditions.     

Performance enhancement of an induction motor by secondaryimpedance control

The paper demonstrates the use of nonresistive secondary control of an induction motor to improve efficiency, power factor and torque. A mathematical algorithm is presented to predict the control requirements in terms of secondary capacitance. The required secondary capacitance is implemented by a novel electronic switching technique that effectively increases the value of the used capacitor. This overcomes the high-capacitance demand and provides a feasible solution. Experimental verification is presented in the results obtained from a small induction motor drive     

Speed and efficiency control of an induction motor withinput-output linearization

A combination of a composite adaptive speed controller and an explicit efficiency control algorithm is proposed to control the speed and power efficiency of the induction motor in this paper. First, the input-output linearization method is used to dynamically decouple the motor speed and rotor flux. Then, a composite adaptive control algorithm is designed to control the speed of the induction motor. At steady-state light-load condition, the magnetizing current command is adjusted on the basis of the product of magnetizing current command and torque current command such that the steady-state power loss is minimum. A PC-based experimental drive system has been implemented, and some experimental results are provided to demonstrate the effectiveness of the presented approach     

A stator resistance estimation scheme for speed sensorless rotor flux oriented induction motor drives

Accurate knowledge of stator resistance is of utmost importance for correct operation of a number of speed sensorless induction motor control schemes in the low speed region. Since stator resistance inevitably varies with operating conditions, stable and accurate operation at near-zero speed requires an appropriate online identification algorithm for the stator resistance. The paper proposes such an identification algorithm, which is developed for the rotor flux-based model reference adaptive system (MRAS) type of the speed estimator in conjunction with a rotor flux oriented control scheme. In this speed estimation method, only one degree of freedom (out of the two available) is utilized for speed estimation. It is proposed to utilize the second available degree of freedom as a means for adapting the stator resistance online. The parallel stator resistance and rotor speed identification algorithm is developed in a systematic manner, using Popov's hyperstability theory. It increases the complexity of the overall control system insignificantly and enables correct speed estimation and stable drive operation at near-zero speeds. The proposed speed estimator with parallel stator resistance identification is at first verified by simulation. Extensive experimentation is conducted next at low speeds of rotation and successful stator resistance identification is achieved down to 0.5-Hz frequency of rotation.     

Adaptive fuzzy-neural-network control for induction spindle motor drive

An induction spindle motor drive using synchronous pulse-width modulation (PWM) and dead-time compensatory techniques with an adaptive fuzzy-neural-network controller (AFNNC) is proposed in this study for advanced spindle motor applications. First, the operating principles of a new synchronous PWM technique and the circuit of dead-time compensator are described in detail. Then, since the control characteristics and motor parameters for high-speed-operated induction spindle motor drive are time varying, an AFNNC is proposed to control the rotor speed of the induction spindle motor. In the proposed controller, the induction spindle motor-drive system is identified by a fuzzy-neural-network identifier (FNNI) to provide the sensitivity information of the drive system to an adaptive controller. The backpropagation algorithm is used to train the FNNI online. Moreover, the effectiveness of the proposed induction spindle motor-drive system is demonstrated using some simulated and experimental results.     

Direct field oriented control scheme for space vector modulated AC/DC/AC converter fed induction motor

This paper investigates a Luenberger flux observer with speed adaptation for a direct field oriented control of an induction motor. An improved method of speed estimation that operates on the principle of speed adaptive flux and current observer has been proposed. An observer is basically an estimator that uses a plant model and a feedback loop with measured stator voltage and current. Simulation results show that the proposed direct field oriented control with the proposed observer provides good performance dynamic characteristics. The induction motor is fed by an indirect power electronics converter. This indirect converter is controlled by a sliding mode technique that enables minimization of harmonics introduced by the line converter, as well as the control of the power factor and DC-link voltage. The robustness of the overall system is studied using simulation for different operating modes and varied parameters.     

Passivity-based sliding mode position control for induction motor drives

In this paper, a passivity-based sliding-mode controller is proposed to control the motion of an induction motor. At first, the induction motor is proved to be a state strictly passive system. Then, a sliding-mode position controller with an adaptive load torque estimator is designed to control the position of the induction motor such that the chattering effects associated with a classical sliding-mode position controller can be eliminated. The stability analysis of the overall position control system is carried out by the passivity theory. The proposed approach is robust with regard to variations of motor mechanical parameters and load torque disturbances. Finally, experimental results are included to demonstrate that good position tracking can be obtained without the rotor flux observer.     

A microcomputer-based induction motor drive system using currentand torque control

This paper proposes an induction motor drive with current and torque control. The current control based on the current error with the current controller yields h_l signal. The torque control based on the torque error with the torque controller yields a h_l signal. According to the h_l signal, the h_l signal and the appropriate voltage vector is selected by using a look-up table to control the induction motor drive to obtain a rapid speed response. The torque controller, current controller, and d-q frame transform are constructed by the hardware which reduce the running time of the microcomputer to obtain a high performance drive. Computer simulations and experimental results demonstrate that the proposed method can obtain a high performance induction motor drive. Meanwhile, employing the advantages of the added zero voltage vector to reduce the inverter switching frequency greatly increasing the efficiency of the inverter     

A space vector modulation algorithm for torque control of inverterfed induction motor drive

After a short review of the vectorial torque control (VTC) strategy, the design and setup of a dedicated modulation hardware unit is described in detail. Experimental comparisons with traditional induction motor control techniques fully confirm the validity of the proposed system     

Speed observer system for advanced sensorless control of induction motor

This paper presents a sensorless control system for induction motors, which is realized on a fixed-point digital signal processor (DSP) and field programmable gate arrays (FPGAs). An observer system has been developed for estimation of speed and the other state variables. The proposed observer system is verified for different conditions of motor operation. Experimental results for the control system fed by voltage source inverter controlled using predictive current controller are presented.     

Design and implementation of PLC-based monitoring control system for induction motor

The implementation of a monitoring and control system for the induction motor based on programmable logic controller (PLC) technology is described. Also, the implementation of the hardware and software for speed control and protection with the results obtained from tests on induction motor performance is provided. The PLC correlates the operational parameters to the speed requested by the user and monitors the system during normal operation and under trip conditions. Tests of the induction motor system driven by inverter and controlled by PLC prove a higher accuracy in speed regulation as compared to a conventional V/f control system. The efficiency of PLC control is increased at high speeds up to 95% of the synchronous speed. Thus, PLC proves themselves as a very versatile and effective tool in industrial control of electric drives.     

A new DC-link converter for induction motor drives

In this paper, a new DC link power converter is proposed for induction motor drives. It consists of a three-phase adjustable AC/DC power converter as a pre-stage, a three-active-switch power converter to simplify the conventional six-active-switch inverter and eliminate the lock-out time circuit and an adaptive DC-link voltage controller to achieve the optimal DC voltage and minimize the switching frequency of the three-active-switch power converter. The simple rotor-flux-oriented control can also be implemented easily using the proposed power converter to achieve high performance. Finally a prototype circuit is constructed and some experimental results are presented for demonstration     

Combined vector control and direct torque control method for high performance induction motor drives

A new control method is proposed for three phase high performance induction motor drives. The control system enjoys the advantages of vector control and direct torque control and avoids some of the implementation difficulties of either of the two control methods. In particular, the proposed control system includes a current vector control in connection with a switching table. An extensive comparative performance evaluation of a motor under the proposed control method confirms the effectiveness of the method and its partial superiority over either vector control or direct torque control despite its relative structural simplicity.     

A new sliding mode position controller with adaptive load torqueestimator for an induction motor

A new sliding mode control algorithm with an adaptive load torque estimator is presented to control the position of the induction motor in this paper. First, the rotor flux is estimated with the simplified rotor flux observer in the rotor reference frame and the feedback linearization theory is used to decouple the rotor position and the rotor flux amplitude. Then, a new sliding mode position controller with an adaptive load torque estimator is designed to control the position of the induction motor such that the chattering effects associated with the classical sliding mode position controller can be eliminated. Stability analysis is carried out using the Lyapunov stability theorem. Experimental results are presented to confirm the characteristics of the proposed approach. The good position tracking and load regulating responses can be obtained by the proposed position controller     

Self-tuning control of induction motor drive using neural networkidentifier

This study presents a new self-tuning PI speed controller with load torque observer and feedforward compensation based on neural network identification for an induction motor. A two-layer neural estimator is also used to provide a real-time adaptive estimation of the unknown motor dynamics. The widely used projection algorithm is used as the learning algorithm for this network, to minimize the difference between the motor's actual response and that predicted by the neural estimator. The proposed neural estimator uses this learning to adjust PI speed controller with a load torque observer to generate the control signal online, thereby bringing the motor output to a desired reference trajectory. The theoretical analysis, simulation and experimental results demonstrate the proposed scheme's effectiveness     

A fuzzy adapted field-oriented mechanism for induction motor drive

The detuning of an indirect field-oriented induction motor drive due to variation of rotor resistance may lead to low efficiency and poor transient response. To improve this, an induction motor drive with a fuzzy adapted field-oriented mechanism is proposed. During steady state conditions, an adapted slip angular speed signal is synthesized by a fuzzy controller and used to adjust the original estimate of slip angular speed signal such that minimum stator current is obtained. When the transient due to command or load torque change occurs, the fuzzy tuning mechanism is temporarily inhibited and the final value of the adapted signal is held. A discrete two-degree-of-freedom controller (2DOF) is designed to yield good speed command tracking and load regulating responses. The effectiveness of the proposed motor drive is demonstrated experimentally     

Temperature rise of an induction motor during plugging

The problem of three-dimensional transient heat flow in the stators of induction motors is solved using a finite-element formulation employing arch-shaped elements. The shape functions and exact solutions are derived algebraically for the utmost economy in computation. The temperature distribution has been determined considering convection from the surface and the two ends. The temperature distribution has also been determined by specifying the temperature of the surface and the ends. A simple cylinder is used as an example. The temperature at different locations in the stator of the induction motor has been computed during transients     

A comparison of induction motor models for bus transfer studies

A study was undertaken to determine if improved accuracy can be obtained using different induction motor models for bus transfer simulations where the loads have low inertias. Bus transfer simulations are presented using five different models. Based on a comparison of these simulations, separate motor models for the disconnect period, the period immediately after reenergization, and the longer time period during which bus voltage and motor speeds are restored are recommended     

A capacitor start three phase induction motor

A scheme for the fast starting of three-phase induction motors is proposed. This scheme is based on starting the motor from a single-phase power supply with the help of a phase balancer properly selected for achieving maximum starting torque. As the speed reaches a predetermined value, a simple centrifugal switch is used to reconnect the motor to the three-phase supply. The feasibility of the proposed scheme is proven through the development of a rigorous state-space mathematical model and its associated digital simulation, followed by experimental verification     

Efficiency increase of an induction motor by improving coolingperformance

Improving the efficiency of induction motors, which are the most energy consuming electric machines in the world, saves much energy. The efficiency can be increased by improving cooling performance as well as by using better materials or by improving electromagnetic performance with better design. This paper presents the relationship between the efficiency or the losses and the temperature of coils with experiments as well as simulations by changing parameters such as the load and the flow rate of cooling air. The losses and the efficiency are calculated from an equivalent circuit method as well as experiments. Coil temperatures variation affects much on the efficiency. The internal cooling method is better than that of external cooling for the coil temperature reduction. Several cooling methods are compared focusing on the fan efficiency and performance, from which the values of the efficiencies of the motors are expected. The fan efficiency as well as the fan performance should be considered for the optimum fan design to increase the total efficiency of a motor. The simulations are validated by the comparison with the experiments