Adjustable Frequency Controllers Research Articles

Test of KW Class Photonic Microwave Generation Using Vanadium-Compensated 6H-SiC PCSS and Burst-Mode-Operation Pulse Laser

Photoconductive semiconductors operating in linear mode can be used for adaptive high-power microwave (HPM) generators by modulating incident light. This paper presents the design scheme and preliminary test results of a narrowband kW class adaptive photonic microwave generator by employing a wide-bandgap semi-insulating 6H-SiC photoconductive semiconductor and a burst-mode laser. The experimental scheme of the generator is described along with the circuit simulation of the radio frequency generator. The laser operated at a wavelength of 532 nm with a pulse width of 100 ns and a repetition rate of 100 Hz. The laser modulates the frequencies of the generated microwave, and preliminary tests are conducted in the frequency range of 0.8–1.2 GHz. The maximum output microwave power of the designed scheme reaches up to 2.6 kW when the bias voltage is 10 kV. The results confirm that this method can be used for high-power frequency-adjustable microwave signal generation. The microwave source system presented in this paper has continuously adjustable frequency and flexible waveform control.

An adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system

An adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system

Design and Experimentation of a Self-Sensing Actuator for Active Vibration Isolation System with Adjustable Anti-Resonance Frequency Controller.

The vibration isolation system is now indispensable to high-precision instruments and equipment, which can provide a low vibration environment to ensure performance. However, the disturbance with variable frequency poses a challenge to the vibration isolation system, resulting in precision reduction of dynamic modeling. This paper presents a velocity self-sensing method and experimental verification of a vibration isolation system. A self-sensing actuator is designed to isolate the vibration with varying frequencies according to the dynamic vibration absorber structure. The mechanical structure of the actuator is illustrated, and the dynamic model is derived. Then a self-sensing method is proposed to adjust the anti-resonance frequency of the system without velocity sensors, which can also reduce the complexity of the system and prevent the disturbance transmitting along the cables. The self-sensing controller is constructed to track the variable frequency of the disturbance. A prototype of the isolation system equipped with velocity sensors is developed for the experiment. The experiment results show that the closed-loop transmissibility is less than −5 dB in the whole frequency rand and is less than −40 dB around, adding anti-resonance frequency which can be adjusted from 0 Hz to initial anti-resonance frequency. The disturbance amplitude of the payload can be suppressed to 10%.

A Study on Surge and Stall under the Interaction of Parallel Axial flow fan in Tunnel

In the ventilation design for tunnels above 10km, an axial flow fan of great power needs to be set in ventilation shafts. There are few provisions on the setting modes and less discussion of parallel axial flow fan mode in the Specifications for Design of Ventilation and Lighting of Highway Tunnels. All of these bring a lot of difficulties about the axial fan selection, layout and control design. There is no specialized research on axial flow fan for tunnels and no studies on surge and stall under the interaction of parallel axial flow fan in tunnel in spite of the more and more application of parallel axial flow fan. So, this paper conducts a study on surge and stall under the interaction of parallel axial flow fan in tunnels. Through the study on the operating principle and analysis of parallel axial flow fan, we can know that the noise will increase suddenly, which will in turn result in fan vibration and running instability once the stall occurs. When a fan surges, the air volume and pressure, the motor current will fluctuate sharply, which brings significantly increased vibration and noise. At the same time, the rotary blade and the shell are subject to considerable stress effects and the fan will possibly suffer from great damage. The surge will occur in the unstable zone of axial fan performance curve. The strong pulsation and periodic oscillation of the air flow will increase the noise, which is a serious damage to the fan. So an axial fan should avoid this zone in running. With two axial flow fans of the same power parallel, the mutual influence is not very great. Therefore this research will focus on the efficiency in the case of two fans with a high and a low power parallel. Stall will occur if the outside pressure is greater than the outlet pressure. Once the stall happens, the noise will increase suddenly, which will in turn result in fan vibration and running instability. When two fans parallel, i.e. when the power ratio of the parallel fans is over 5.3, the possibility of the small fan's stall is high, otherwise it is small. With regard to the running efficiency of parallel axial flow fans and the starting safety, it is better to parallel two fans, and the fans with adjustable movable vanes or frequency control or the ordinary nonadjustable fans can be used.

Bi-directional power electronic transformer with maximum power-point tracking capability for induction heating applications

A single-stage commercial low frequency to high AC frequency bi-directional power electronic transformer (PET) for induction heating applications is proposed here. The proposed PET can simultaneously track the maximum power point and improve the output power factor by using a phase locked loop adjustable switching frequency controller. The operating principle of the PET is discussed based on mathematical equations and equivalent circuits. The experimental results of laboratory prototype, which converts 110 V/3φ/50 Hz input voltage to 20 V/1φ/22 kHz output voltage, show the capabilities of the proposed PET.

Proper application of motors operated on adjustable frequency control

Most high-efficiency motors can withstand the rigors of adjustable speed drive (ASD) operation. However, there are significant differences between applications of motors operated on sinewave power and motors operated on adjustable frequency controls (AFCs). This is an ongoing subject, rapidly changing due to advances in the technology of the AFCs. Subsequently, many of the older problems associated with the application of motors on AFCs have been solved, while at the same time, new problems were introduced. In many cases, high-efficiency, low-voltage motors can be applied on AFCs with no or little modification. In order to do this successfully, however, basic motor operating principles and the affect of applying a motor on an AFC need to be understood. The proper application of a motor for use on an ASD is dependent on an understanding of: thermal motor limitation-from AFC harmonics and reduced-speed operation at constant load (i.e., constant torque); and upper-speed limitation (beyond base speed)-constant power electrical limitation and mechanical upper-speed limitation. This article targets the application of motors not specifically designed for AFC operation. Generally, NEMA motors (i.e., motors up to the 440 frame) are more apt to be indiscriminately applied on AFCs than above-NEMA (ANEMA) motors (i.e., motors larger than the NEMA frame sizes). The concepts/guidelines presented here are equally applicable to both NEMA and ANEMA motors.

Applying Adjustable Frequency Controllers to High-Starting-Torque Loads

Applying Adjustable Frequency Controllers to High-Starting-Torque Loads

Need for industry standards for AC induction motors intended for use with adjustable-frequency controllers

With the increased use of AC induction motors on adjustable-frequency controls (AFCs) offered in a wide variety of types, there is a need to develop industry standards to provide the guidance necessary for the proper selection of the motor, which will function as intended with the control. These new standards should establish requirements for both electrical and mechanical characteristics of the motor necessary to establish uniformity within the industry. The items that must be covered by such industry standards in order to assure successful applications on adjustable frequency are discussed. Proposals for the content of the standards are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Incremental method of pulse width modulation for three-phase inverters

Abstract A novel pulse-width modulation technique for three-phase voltage-controlled inverters is presented. Description of a microprocessor-based modulator capable of completing in real-time all the computations required for adjustable frequency, magnitude and phase control of the inverter output voltage is provided. Experimental results are given.

The application of adjustable-frequency controllers to forced-draft fans for improved reliability and energy savings

A method of utilizing an adjustable-frequency controller (AFC) with a line bypass, to provide the energy saving potential of an AFC coupled with the inherent reliability of a simple magnetic starter, is presented. The proposed system allows the transfer of the motor between the AFC and the power line, even after a controller fault or power interruption, without causing a significant loss of air. A specific operating application is reviewed. The operating experience for the first year for this AFC on a forced draft (FD) fan has met the expectations of the user and manufacturer. When operating this FD fan from the main control panel, the operating procedure remains the same in either the AFC or bypass mode.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Application of Adjustable Frequency Controllers to Forced Draft Fans for Improved Reliability and Energy Savings

A method for utilizing an AFC with a line bypass to provide the energy saving potential of the AFC coupled with the inherent reliability of the simple magnetic starter is presented. The proposed system allows transfer of the motor between the AFC and the power line, even after a controller fault or power interruption, without causing a significant loss of air. A specific operating application is reviewed.

Considerations in Testing and Stabilizing Frequency Beating of a Current Source Inverter

It is generally believed that the current-source inverter adjustable frequency controller with auto sequential commutation cannot be easily tested without a load motor connected. However, it is shown that the controller can, in fact, easily be tested without a load motor by adding some simple circuits in both the regulator and power circuit and by following step-by- step test procedures. The frequency beating phenomenon inherent in the current-source inverter and an effective compensating technique are also presented and explained.

Considerations in Applying Induction Motors with Solid- State Adjustable Frequency Controllers

Considerations in applying ac motors with solid-state adjustable -frequency controllers are discussed, and guidelines. are offered where possible. As a background, three commonly used at drive techniques are reviewed. Test data are provided for 100-hp standard and energy-efficient designs operated on each of the three types of drives.

Application Considerations for AC Drives

General application considerations for ac variable-frequency drives are discussed. A review of induction motor characteristics and adjustable frequency controller fundamentals is presented as a background for applying the drives. In addition, a brief review of the types of controllers available is provided. General application guidelines are then presented.

Digital Applications of AC Motor Controls

The rapidly developing field of adjustable frequency control of ac motors represents more than just the evolution of a technology for solving old problems in a different way. More importantly, it is bringing into being a power output element capable of doing new jobs and of dramatically simplifying many jobs that have been done in the past with considerable complexity and hardware and not very well. A key to its promise lies in its basic nature which is inherently more digital than analog and therefore capable of being readily integrated into digital systems and of interfacing easily with those sources of digital signals such as thumbwheels, digital tachometers, encoders, tape readers, and process computers which abound in modem industrial systems.

Adjustable frequency control of high-speed induction motors

The aviation industry has found numerous applications for high-speed squirrel cage motors to operate over a wide speed range. Elaborate power supply systems have been developed to provide the required range and accuracy of motor speed control. Applications of the systems probably will be found in other industries.

Adjustable Frequency Control of High-Speed Induction Motors

The aviation industry has found numerous applications for high-speed squirrel cage motors to operate over a wide speed range. Elaborate power supply systems have been developed to provide the required range and accuracy of motor speed control. Applications of the systems probably will be found in other industries.