A Temperature-Compensation Technique for Improving Resolver Accuracy

Variation in the ambient temperature deteriorates the accuracy of a resolver. In this paper, a temperature-compensation technique is introduced to improve resolver accuracy. The ambient temperature causes deviations in the resolver signal; therefore, the disturbed signal is investigated through the change in current in the primary winding of the resolver. For the proposed technique, the primary winding of the resolver is driven by a class-AB output stage of an operational amplifier (opamp), where the primary winding current forms part of the supply current of the opamp. The opamp supply-current sensing technique is used to extract the primary winding current. The error of the resolver signal due to temperature variations is directly evaluated from the supply current of the opamp. Therefore, the proposed technique does not require a temperature-sensitive device. Using the proposed technique, the error of the resolver signal when the ambient temperature increases to 70 °C can be minimized from 1.463% without temperature compensation to 0.017% with temperature compensation. The performance of the proposed technique is discussed in detail and is confirmed by experimental implementation using commercial devices. The results show that the proposed circuit can compensate for wide variations in ambient temperature.

EXPERIMENTAL STUDY OF STATIC CHARACTERISTICS ASYNCHRONOUS MACHINE IN DYNAMIC BRAKING MODE WITH INDUCTION RESISTANCE IN THE ROTOR WINDING

The article discusses the results of a study of the static electromechanical characteristics of an asynchronous machine (AM) when prototypes of induction resistances (IR) with improved parameters are included in its rotor circuits. The dynamic braking (DB) of asynchronous machines, which is widespread in practice, provides for the dissipation of the kinetic energy of the rotating parts in the resistance boxes included in the rotor winding. In the process of stopping, to maintain a constant average braking torque AM, a bulky relay-contactor circuit for shunting rotor resistances is used. However, it is not possible to eliminate significant fluctuations in the electromagnetic torque in this way. To optimize the DB AM process, it is proposed to include a three-phase IR in the rotor winding instead of resistance boxes, the value of which automatically decreases along with the rotor current frequency. This approach allows you to abandon contact equipment and ensure smooth braking of the machine with fluctuations in the electromagnetic moment in narrower limits. The known IR designs are designed for starting modes of induction motors with a wound rotor, but they cannot ensure the constancy of the torque on the AM shaft in the DB mode. Therefore, the purpose of the study is to develop and experimentally confirm the effectiveness of simple control circuits of an induction machine in the specified mode with improved contactless induction rheostats in the rotor. The paper presents a diagram of a pilot plant and a figure explaining the design features of the IR. The studies were carried out for an asynchronous machine of the MTB-412-8 type, equipped with a thyristor exciter and a tachogenerator. The three phases of the AM rotor included ICs connected by a "star". The experiments were carried out in the direction of obtaining the necessary braking characteristics of the AM by varying the switching circuit of the stator phases and the value of the current supplying them. The figures show the mechanical characteristics of AM, obtained in the process of studying the influence on them of three typical circuits for switching on the phases of the stator winding and two values ​​of the fixed supply current. The research results show that the desired form of the mentioned AM characteristics is achieved only when using the stator phase switching in a function of the rotor speed and a constant supply current value.

Spectral analysis of the supply current of the rl load with a voltage regulator based on a pulse-line converter

Pulse-width voltage regulators are gaining increasing use in industry, especially in variable speed drives. At the same time, little research has been done in the field of electromagnetic compatibility (spectral composition of current consumption). The aim of the study is to determine, using computer simulation, the nonsinusoidality of the current consumption with an RL-load from a voltage regulator based on a pulse-width conversion. The study of the spectral composition of the supply current of an active-inductive load with a pulse-width voltage regulator was carried out using the provisions of the theory of electrical circuits of sinusoidal and non-sinusoidal periodic current using computer simulation. To analyze the spectral composition of the supply current of the RL-load with the selected voltage regulator, a simulation computer model was created, which consisted of a three-phase power supply and an RL-load, a rectifier with a transistor switch. The regulation of the applied voltage to the consumer was carried out according to the principle of a pulse-width voltage converter. As a result of studying a model of a regulated power supply based on a pulse-width converter and working on an active-inductive load, it was found that even with an initial voltage of the fundamental harmonic regulator of 34 V, the nonsinusoidality of the consumption current is 0.19%, which corresponds to the quality standard for electricity. It is advisable to use this regulator for a controlled electric drive of ventilation systems with an increased slip motor, for example, in "Climate-4M" units. Key words: semiconductor voltage converter, pulse-width converter, higher harmonics, RL-load

Application of Transient Electromagnetic in Detection of Water Accumulation in Broad Coal Mine

In view of the problem of serious water accumulation and frequent accidents in the coal mine mining area, the distribution range of Yuzhou Shenhuo Kuanfa Mining Coal (hereinafter referred to as Kuanfa Coal Mine) is detected by transient electromagnetic method. The transient electromagnetic emission wire frame is 480m × 480m, frequency is 8Hz, power supply current is 16A. The research conclusion preliminarily determines that the transient electromagnetic and controllable source audio earth electromagnetic method is applicable for the exploration of the mined space area in Yuzhou mining area, and the construction parameters provide a reliable reference for the accurate exploration of the mined space area in Kuanmining area.

A new flowchart for parameters calculation of Hybrid Active Power Filter with Injection Circuit

This paper presents a new flowchart for parameters calculation of Hybrid Active Power Filter with Injection Circuit (IHAPF). The first is the necessity to use the IHAPF model and the parameters of the IHAPF needed to search have been shown. Next, the constraints of the parameters to be searched and the objective function to be reached are given. Since then a flowchart is designed to look for parameters of IHAPF using the Jaya optimization algorithm. The Jaya algorithm has the advantage of simplicity, few parameters, and good performance. Therefore it reduces search time. Compared to the flowchart using the firefly algorithm, particle swarm optimization algorithm, and simulated annealing algorithm, the simulation results performed on an IHAPF 10kV-50Hz model have proven that: the proposed flowchart gives better results in minimizing the compensation errors, minimum phase shift angle between supply current, and source voltage, minimum total harmonic distortion of supply current.

Design of the Class-E Power Amplifier with Finite DC Feed Inductance under Maximum-Rating Constraints

This paper proposes an analytical expression set to determine the maximum values of currents and voltages in the Class-E Power Amplifier (PA) with Finite DC-Feed Inductance (FDI) under the following assumptions—ideal components (e.g., inductors and capacitors with infinite quality factor), a switch with zero rise and fall commutation times, zero on-resistance, and infinite off-resistance, and an infinite loaded quality factor of the output resonant circuit. The developed expressions are the average supply current, the RMS (Root Mean Square) current through the DC-feed inductance, the peak voltage and current in the switch, the RMS current through the switch, the peak voltages of the output resonant circuit, and the peak voltage and current in the PA load. These equations were obtained from the circuit analysis of this ideal amplifier and curve-fitting tools. Furthermore, the proposed expressions are a useful tool to estimate the maximum ratings of the amplifier components. The accuracy of the expressions was analyzed by the circuit simulation of twelve ideal amplifiers, which were designed to meet a wide spectrum of application scenarios. The resulting Mean Absolute Percentage Error (MAPE) of the maximum-rating constraints estimation was 2.64%.

Stability Analysis of Shunt Active Power Filter with Predictive Closed-Loop Control of Supply Current

This paper presents a shunt active power filter connected to the grid via an LCL coupling circuit with implemented closed-loop control. The proposed control system allows selective harmonic currents compensation up to the 50th harmonic with the utilization of a model-based predictive current controller. As the system is fully predictive, it provides high effectiveness of the harmonic reduction, which is proved by waveforms achieved in performed tests. On the other hand, the control system is prone to loss of stability. Therefore, the paper is focused on the stability analysis of the discussed control system with the additional outer control loop of the supply current with predictive control of this current. The conducted stability analysis encompasses the assessment of system stability as a function of the coupling circuit parameter identification accuracy, whose values are implemented in the current controller, as well as parameters such as the sampling frequency and proportional–integral (PI) controller coefficients. The obtained results show that the ranges of the LCL circuit parameter identification accuracy for which the system remains stable are relatively wide. However, the most effective compensation of the supply current distortion is achieved for the parameters identified correctly, and the greatest impact on the compensation quality has the value of L1 inductance.

Влияние термических сопротивлений на холодильный коэффициент термоэлектрической системы охлаждения

A thermoelectric cooling and temperature control system consisting of a thermoelectric module and devices for supplying and removing heat is considered. Based on a mathematical model that uses the operating characteristics of a serial thermoelectric module as initial data, the cooling coefficient of the cooling system was calculated taking into account the thermal resistances of the devices for supplying and removing heat. The dependences of the cooling coefficient on the current strength for different values of the cooling parameters are obtained. The analysis of optimal values of the power supply current of the thermoelectric module is carried out.