Stator Winding Resistance Research Articles

Indirect temperature protection of an asynchronous generator by stator winding resistance measurement with superimposition of high-frequency pulse signals

The article deals with the indirect methods for calculating the temperature of asynchronous generators with the introduction of a pulse component in the power supply circuit of the stator windings of asynchronous generators with squirrel-cage rotor. The relevance of this issue is determined by the need to improve asynchronous energy converters to increase their reliability and safety. The object of the study is an asynchronous generator with squirrel-cage rotor, which consume 40 % of the total electricity generated, and are the most affordable. One of the dangerous modes of asynchronous generators is their overheating as a result of increased currents and temperatures. The thermal protection of the stator winding of asynchronous generators relies primarily on measuring or determining the winding temperature. An indirect method for determining temperature based on measuring the resistance of the stator of an asynchronous generator with squirrel-cage rotor is proposed. The method is based on superimposing pulse signals of small amplitude and high frequency of 600 Hz on an alternating sinusoidal voltage with a frequency of 50 Hz. A simulation model for a 3 kW asynchronous generator has been developed. There were given the simulation results. The estimated values of the active resistances of the stator can be used to indirectly determine the temperature of the windings in thermal protection devices of asynchronous generators, as well as for control, monitoring and diagnostics of the technical condition. The research results confirm the possibility of indirect temperature determination and the creation of a thermal protection system for asynchronous energy converters based on the use of estimation methods.

PF-MRAC-Based Elimination of Sensors in Solar-Powered PMSM Drive-Based Water Pumping System

The water pumping system powered by solar photovoltaic (PV) array and driven by permanent magnet synchronous motor demands a current-sensor to operate PV array at its maximum power and an encoder to implement field-oriented control of motor. Reduction in reliability and increment in system cost are the two major drawbacks that demands their elimination. Even the application of system for locations with high ambient temperature is limited as these sensors are temperature sensitive. In this work, power-factor based model-reference adaptive-control (PF-MRAC) to remove encoder as well as current-sensor is presented. Even stator winding resistance and rotor flux linkage are estimated by PF-MRAC. Thus, presented MRAC is independent of parameter uncertainty contrary to conventional MRAC. Besides, developed PF-MRAC does not contain integral and derivative operators, and hence it is free from saturation and noise problems. The estimated speed is used for estimation of PV power, which is then used for extracting maximum power from PV array, thereby removing current sensor. Besides, an additional converter is not required for realization of presented maximum power point tracking method. The developed PF-MRAC is realized on dSPACE Microlab box platform, and test results are acquired for various operating scenarios on laboratory prototype.

Development of Integrated Softcomputing Approach for Stator Resistance Estimation of Three Phase Induction Motor

In this paper, an integrated quantum inspired GA (QGA) based generalized neural network (QGA–GNN) has been developed. The QGA–GNN is used for estimation of stator resistance of a 5 hp three phase induction motor (3Φ I.M.) under different healthy and unhealthy working conditions. The experimentation is performed in the laboratory for estimating stator winding resistance under healthy and faulty (i.e., 10, 20, 30, or 40% short circuited) conditions. The motor current and motor speed are considered as input and stator resistance as output of the proposed technique. The results obtained from QGA–GNN are compared with the ANN and GNN. QGA–GNN is giving good results under different working conditions.

Doğrudan moment kontrolüne stator direncinin etkisinin incelenmesi ve sürekli mıknatıslı senkron motora uygulaması

Permanent magnet synchronous motors are a type of motor that is becoming more and more popular due to some superior features together with the technological developments in power electronics. The fact that these motors can produce maximum torque even at zero speed, low maintenance costs and high power/weight ratio has increased their use. In this study, the direct torque control method from vector control methods was used. This method has been investigated by considering the change in the stator winding resistance caused by the temperature increase depending on the operation of the motor and has been applied to a permanent magnet synchronous motor by using a voltage-sourced voltage-controlled inverter circuit. The modeling of the electric motor has done with the d-q model and this model has used in the simulation study. In order to realize the direct torque control of the motor, torque and flux calculations have been made using the current and voltage data applied to the motor. The obtained flux and torque errors have been applied as input to the hysteresis comparator. The switching strategies in the pulse width modulation method used in the inverter control have realized the torque and speed control of the permanent magnet synchronous motor by using the data obtained from the hysteresis output. The variation of winding resistance with temperature and its effect on different speeds and torque control of the motor has been investigated by keeping all other motor parameters constant. The effect of the stator winding resistance on the speed and torque control of the motor has been shown in simulation studies.

Effects of induction machine parameters on its performance as a standalone self excited induction generator

A squirrel cage induction machine (SCIM) when aggregated with relevant capacitances and a prime mover, acts as self-excited induction generator (SEIG). As it hosts energy conversion the parameters of SCIM have considerable impact on the power extraction capability of SEIG. An aspect which is missing from the available research on SEIGs is evaluation of the affects of its rotor’s moment of inertia (J) and per-phase stator winding resistance (Rs) on performance indices. This work investigates the impacts of these factors on a SCIM’s performance as series compensated, short shunt SEIG. The study considers two distinctly designed SCIMs, in terms of J and Rs, operated as SEIG. In order to simulate their performance a stationary reference frame dq model including non-linear saturation and cross coupling effects is developed and verified experimentally. Several key investigations based on series capacitance selection, losses and efficiency, on-load performance with different power factor loads, transient performance with load perturbation and variable speed operation are carried out. The study reveals that SEIG with high J and lower Rs gives considerably better performance than its counterpart. The conclusions reported in the study are important especially for standalone/off grid application of SEIGs.

Multiparameter Identification of Permanent Magnet Synchronous Motor Based on Model Reference Adaptive System—Simulated Annealing Particle Swarm Optimization Algorithm

The accurate identification of permanent magnet synchronous motor (PMSM) parameters is the basis for high-performance drive control. The traditional PMSM multiparameter identification method experiences problems with the uncertainty of the identification results and low identification accuracy due to the under-ranking of the mathematical model of motor control. A multiparameter identification of PMSM based on a model reference adaptive system and simulated annealing particle swarm optimization (MRAS-SAPSO) is proposed here. The algorithm first identifies the electrical parameters of the PMSM (stator winding resistance R, cross-axis inductance L, and magnetic linkage ψf) by means of the model reference adaptive system method. Second, the result is used as the initial population in particle swarm optimization identification to further optimize and identify the electrical and mechanical parameters (moment of inertia J and damping coefficient B) in the motor control system. Additionally, in order to avoid problems such as premature convergence of the particle swarm in the optimization search process, the results of the adaptive simulated annealing algorithm to optimize multiparameter identification are introduced. The simulation experiment results show that the five identification parameters obtained by the MRAS-SAPSO algorithm are highly accurate and stable, and the errors between them and the real values are below 2%. This also verifies the effectiveness and reliability of this identification method.

Пускові режими асинхронних електроприводів з урахуванням опору лінії системи електропостачання

The issues of the influence of the active resistance of the power supply line on the starting characteristics of asynchronous electric drives are considered. In long-distance low-voltage distribution networks, the voltage at the end consumers may decrease due to a significant drop in the power line. This voltage drop will depend on the amount of current in the line. Starting unregulated induction motors with short-circuited rotor is characterized by a relatively small value of starting torque at high starting current values, which will increase the voltage drop in the transmission line during start-up and, consequently, reduce starting torque proportional to the square of applied voltage. Thus, the mode of operation of the electric drive with frequent starts will negatively affect the operation of other consumers of electricity. A comparison of starting characteristics using a serial asynchronous motor with a short-circuited rotor and modified with massive end ferromagnetic screens of rotor circuit elements outside the working air gap, which provides the formation of mechanical characteristics of the “excavator” type. The influence of the active resistance of the transmission line on the values of starting torques and currents for electric drives with both types of motors is investigated. It is established that the modified asynchronous motor due to the larger value of the starting torque allows to start the electric drive at static torque equal to the nominal torque of the motor at the studied change of line resistance to 1.5 relative to the active resistance of the motor stator winding, while in electric drive serial motor starting torque becomes less than the nominal with additional resistances greater than 0.8 relative to the active resistance of the stator winding. In turn, higher values of starting torque provide the electric drive with the modified asynchronous motor much less time of start and consumption of active energy, than at application of the serial car with identical conditions of start. Thus, the electric drive with an induction motor with massive end ferromagnetic screens of fragments of the rotor circuit outside the working air gap has significant advantages over the serial motor in the case of operation with frequent starts.

Estimation of temperature in turbo-molecular pump based on motor resistance online identification

The temperature of the turbo-molecular pump (TMP) system has to be monitored in real-time for long stable operation in a high vacuum environment. Since the high-speed motor is the major heat source of the TMP system, the thermal sensors such as Pt100 are widely used to measure the temperature via being embedded in the motor stators. However, these thermal sensors require extra wires and signal conditioning circuits, which increase the complexity of installation. In order to solve this problem, a real-time online estimation method for the temperature of the TMP driven motor is proposed in this paper. First of all, the resistance identification model of the high-speed motor used in TMP system is built. After that, an improved recursive least squares (RLS) algorithm, which introduces a discount factor to overcome the problem of data saturation and weak dynamic tracking, is used to identify the resistance of the motor stator windings. Then, the temperature of the TMP could be estimated indirectly based on the linear relationship between the motor stator resistance and the temperature. At last, the proposed method is tested in a self-developed magnetically levitated turbo-molecular pump (MLTMP) system, and the experimental results verify its validity and reliability.

DC-Current Injection With Minimum Torque Ripple in Interior Permanent-Magnet Synchronous Motors

Several proposals based on dc-current injection have been reported for estimating the stator winding resistance in induction machines, and recently extended for synchronous machines. Tracking this resistance can be very useful, e.g., for thermal monitoring or preserving control dynamics. In surface-mounted permanent-magnet synchronous machines (PMSMs), it is possible to inject a dc component in the $d$ -axis, without perturbing the torque. However, it has been claimed that, for synchronous machines with saliency, it is not possible to avoid the torque ripple due to such injection. This letter proposes optimum reference currents to impose dc current in three-phase interior PMSMs while minimizing to practically zero its associated torque ripple. Namely, the dc signal is injected in combination with a suitable second-order harmonic so that the stator current space vector follows the constant-torque locus, while the fundamental is set according to the maximum-torque-per-ampere strategy. Experimental results validate the theory.

Estimation Method of Stator Winding Resistance for Induction Motor Drives Based on DC-Signal Injection Suitable for Low Inertia

Thermal protection is an important aspect that should be considered in ac machines to prevent reduction of the lifetime. For economic reasons, temperature estimation is preferable than the installation of thermal sensors. Thus, several proposals based on dc-signal injection have been reported. Their main drawback is that a certain torque ripple is produced during the injection. On the other hand, the already published filtering techniques proposed to extract the dc components from the phase voltages and currents are based on transforming the per-phase variables to a synchronous reference frame where the fundamental component is eliminated. For this transformation, the rotor position is needed. It is shown in this paper that, due to the disturbance caused in the position due to the torque ripple, the stator resistance estimation is deteriorated when the inertia is not high enough to make this perturbation negligible. In addition, a new technique is also presented to segregate the dc components from the phase currents and voltages, which is robust in terms of accuracy even when the speed/position is perturbed due to the injection. Experimental results validate the theory.

Modeling of Sensorless Determination of the Resistance and Temperature of the Stator and Rotor Windings of an Asynchronous Motor

A brief survey of the existing sensorless methods of determination of the temperature of the stator and rotor windings of the asynchronous motors (AMs) is given. It is stated that one of such methods is indirect determination of the temperature by measuring the active resistance of the AM windings. on the AM equivalent circuit, the possibility of determining the resistance by introducing the additional components of the stator winding voltage is theoretically justified. The conditions for the correct determination of the parameters when introducing the ac voltage component are stated. The features of the AM mathematical model and method of modeling of determination of the winding resistance in the Matlab packet are studied. The results of modeling determination of the stator winding resistance by introducing the direct voltage component and rotor winding resistance by introducing direct and high-frequency voltage components are presented. The influence of the introduced voltages on the electromechanical coordinates of the electric drive is analyzed. Proposals on selection of the frequency of the ac voltage component are given. An estimation of feasibility of the suggested method in modern electric drive control systems is made.

Coreless AFPM Pulsed Alternator With Low Internal Inductance

The linear induction launcher consists of two parts: the barrel section and the projectile section. The barrel contains of a long coaxial sectionalized group of coils that are energized by a capacitor bank or generator sets. This paper deals with the design, implementation, and experimental test of a coreless axial-flux permanent magnet (AFPM) pulsed alternator with a flywheel system as an energy source for linear induction coil launchers. The proposed coreless AFPM generator has a low internal inductance and resistance of stator windings without compensation windings when compared with the conventional iron core machines. This paper describes the coreless AFPM generator configuration and shows the simulation findings.

Analysis and Improvement of Adaptive Coefficient Third Harmonic Voltage Differential Stator Grounding Protection

This paper presents a novel third harmonic voltage differential stator grounding protection (THV-DSGP) method combining the adaptive coefficient and fixed coefficient. It can solve the protection sensitivity degradation problem when the insulation resistance of stator winding to ground is slowly declining. This protection method retains the advantages of the adaptive coefficient, which is to maintain high sensitivity in case of an instantaneous ground fault. Moreover, the fixed coefficient can remember the initial insulation state of the stator winding and prevent relay failure when the stator insulation is slowly declining. In addition, due to zero-sequence voltage disconnection (ZSVD) often leading to malfunctioning of the THV stator ground protection, the existing criterion of the ZSVD was improved according to the electrical characteristics of the generator when ZSVD happens. THV-DSGP with both adaptive coefficient and fixed coefficient was simulated in the Matlab/Simulink. The simulation results show that the proposed protection can be applied to the slow ground fault of the stator winding. Furthermore, the improved criterion of ZSVD can effectively distinguish the stator metal earth fault and the secondary loop break of the zero-sequence voltage.

Novel Flux Linkage Estimation Algorithm for a Variable Flux PMSM

This paper presents a novel algorithm for online rotor flux linkage estimation for a variable flux interior permanent magnet synchronous machine drive system at different flux density levels. A modified adaptive nonlinear filter is used to instantaneously estimate the amplitude, phase angle, and frequency of the major back EMF harmonic components, from which the total air-gap flux linkage is estimated. The algorithm avoids the averaging method that depends only on the fundamental back EMF component in estimating the air-gap flux linkage. The d -axis inductance versus current measurement test is performed at variable magnetization states to account for the d -axis inductance variation when estimating the rotor flux linkage. Since the stator winding resistance is temperature dependent, a thermocouple is used to obtain the actual stator winding temperature for accurate stator winding resistance measurement. The core loss resistance has been neglected for simplicity. The method was experimentally evaluated for different magnetization states and showed a good performance in tracking the rotor flux linkage variations. The method was tested for field-oriented control (FOC) schemes ( ${\boldsymbol{i}_{\boldsymbol{d}}} = 0$ ) and for FOC with the negative $d$ -axis current operation as well.

Application of Adaptive PSO and Adaptive Fuzzy Logic Controllers to Speed Control PMSM Motor Servo Systems

Three phases Permanent Magnet Synchronous Motors (PMSM) are non-linear resistors, resistance of stator winding, air gap flux, cross-coupling, saturation variable times and cogging torque in operation. Due to the nonlinear nature of PMSM, it is a challenge to control exactly the speed, torque and position. This paper presents two methods for speed control stabilization of the PMSM using the Adaptive Fuzzy Logic - Proportional Integral Derivative controller (AFL-PID) and Adaptive Particle Swarm Optimization - Proportional Integral Derivative controller (APSO-PID). The response results of the speed control PMSM Servo Systems use AFLC-PID and APSO-PID methods are compared and the conclusions are given.

Online temperature monitoring of a grid connected induction motor

This paper proposes a novel method for continuous temperature measurement of the stator winding of an induction machine. The method is based on measuring stator winding resistance by injecting a DC current test signal into the motor neutral point without interrupting its normal operation. The entire stator winding is used as a sensor without additional thermal sensors, while DC voltage and current need to be measured solely. Virtually equal currents are injected in each phase thereby minimizing the influence on the motor torque inherent to contemporary signal injection-based methods. The measurement results obtained using the proposed method are compared to results obtained using the standard resistance-based method and direct measurements obtained from thermocouples embedded in the windings. An excellent match is achieved under various loading levels and variable cooling conditions, thus proving the accuracy and robustness of the proposed method.

Novel Compensation Method to Reduce Rotor Position Estimation Error and Torque Reduction in Signal Injection Based PMSM Drives

High frequency signal injection techniques are widely used to extract rotor position information from low speed to stand still. Accuracy of estimated rotor position is decreased when stator winding resistance is neglected. Position estimation error also results in output Torque reduction. Parasitic resistance of stator winding causes significant position estimation error <br /> and Torque reduction, if not compensated. Signal injection techniques developed in the literature does not provide detailed analysis and compensation methods to improve rotor position estimation of PMS Motors, where stator winding resistance cannot be neglected. This work analyzes the stator winding resistance effect on position estimation accuracy and proposes novel compensation technique to reduce the position estimation error and torque reduction introduced by stator winding resistance. Prototype hardware of a self-sensing PMSM drive is developed. The effectiveness of the proposed method is verified with the MATLAB/Simulink simulations and experimental results on a prototype self-sensing PMSM drive.

Stator and Rotor Faults Monitoring of the Inverter-Fed Induction Motor Drive using State Estimators

The paper deals with the application of the Extended Kalman Filter and the Extended Luenberger Observer algorithms for the stator and rotor fault detection of the induction motor fed by PWM inverter. The induction motor conditions are analyzed using estimated rotor and stator-winding resistance. Mathematical models of the extended state estimators are presented, in which the stator and rotor resistances are added as additional electromagnetic state variables. Experimental results for the inverter-fed induction motor, with shorted stator-turns and broken rotor bars, are presented and analysed.

Estimating the parameters of induction motors in different operating regimes from a set of data containing the rotor cage temperature

The purpose of this paper is to propose a method for accurate estimation of the equivalent circuit parameters of induction motors at different operating regimes from a set of measurement data containing the rotor cage temperature and rotor resistance at 25 $$^{\circ }$$ C. Besides these rotor quantities, the method requires the measurement of supply voltage, stator current, frequency, speed, load torque, stator winding temperature and stator winding resistance at 25 $$^{\circ }$$ C. It is assumed that stator leakage reactance, core-loss resistance, friction and windage losses and stray load losses corresponding to the nominal operation are known. The proposed method iteratively determines air gap voltage, power factor and some other parameters. The effects of temperature change, frequency change, magnetic saturation and stray load losses are taken into consideration. The application of the method is discussed within the existing examples of five different motors. Excellent accuracy is achieved using the proposed method.

Simulation of an interturn fault in a stator winding of a synchronous condenser

A method of simulation of interturn faults in a stator winding in steady state operating conditions of synchronous condenser is proposed. The method is based on a mathematical model with the equations of the mesh current method for phase-to-phase voltages. Expressions for active and reactive impedances of the windings are presented. The initial data for calculation of resistance and reactance of stator and rotor windings are obtained experimentally. Experiments proved that the proposed method simulates interturn faults in a stator winding with a maximum error of 5–10%.