Walter Kaiser

Comparison of fluorescent lamp stabilization methods in the current-fed push-pull inverter

The high frequency current-fed push-pull resonant inverter is suitable for fluorescent lamp electronic ballasts supplied by low DC voltages. The lamp stabilization can be either inductive or capacitive. This paper provides a comparative analysis, an analytical step-by-step design procedure and a sensitivity analysis of lamp power due to component tolerances for both methods. A current crest factor analytical expression for capacitive stabilization is derived. Design performance is evaluated by measurements on a prototype.

Hybrid electronic ballast operating the HPS lamp at constant power

A hybrid solid-state ballast that operates high-pressure sodium (HPS) lamps at main frequency with constant power through rated life is described. The system utilizes two inductors connected in series and a bidirectional semiconductor switch connected in parallel to one of them. A lamp starting circuit has also been included in the ballast. The static switch, with phase angle control provided by power feedback, actuates on lamp current, compensating variations of the main voltage and increases of lamp arc voltage. The system offers the following: (1) an increase of lamp life and system lumen maintenance; (2) power factor and total harmonic distortion of line current comparable to conventional lag ballast; and (3) operating cost savings, both in terms of energy cost and lamp replacement cost.

Speed Neuro-fuzzy Estimator Applied To Sensorless Induction Motor Control

This work proposes the development of an Adaptive Neuro-fuzzy Inference System (ANFIS) estimator applied to speed control in a three-phase induction motor sensorless drive. Usually, ANFIS is used to replace the traditional PI controller in induction motor drives. The evaluation of the estimation capability of the ANFIS in a sensorless drive is one of the contributions of this work. The ANFIS speed estimator is validated in a magnetizing flux oriented control scheme, consisting in one more contribution. As an open-loop estimator, it is applied to moderate performance drives and it is not the proposal of this work to solve the low and zero speed estimation problems. Simulations to evaluate the performance of the estimator considering the vector drive system were done from the Matlab/Simulink software. To determine the benefits of the proposed model, a practical system was implemented using a voltage source inverter (VSI) to drive the motor and the vector control including the ANFIS estimator, which is carried out by the Real Time Toolbox from Matlab/Simulink software and a data acquisition card from National Instruments.

Impact of Current Crest Factor at High and Low Frequency Operation on Fluorescent Lamp Electrodes

The current crest factor (CCF) is a measure of wave shape distortion and indicates the potential for high peak current, which can damage the lamp electrode and reduce lamp life. The value of 1.7, which is regarded as an acceptable limit by the American National Standards Institute (ANSI) and International Electricity Commission (IEC) ballast performance standards is based on 50/60 Hz operation. High frequency operation involves different electrode operating conditions and the validity of this limit could be questionable. This paper evaluates the relative effect of waveform distortions at high-frequency and the low frequency amplitude modulation of high frequency sinusoidal waveforms on electrode emitter depletion with respect to 60 Hz sinusoidal current steady state operation. The emission of electrode mix is evaluated by barium line measurements and cathode fall monitoring on special-made lamps with clear ends

Open-loop neuro-fuzzy speed estimator applied to vector and scalar induction motor drives

Abstract Scalar and vector drives have been the cornerstones of control of industrial motors for decades. In both the elimination of mechanical speed sensor consists in a trend of modern drives. This work proposes the development of an adaptive neuro-fuzzy inference system (ANFIS) angular rotor speed estimator applied to vector and scalar drives. A multi-frequency training of ANFIS is proposed, initially for a V / f scheme and after that a vector drive with magnetizing flux oriented control is proposed. In the literature ANFIS has been commonly proposed as a speed controller in substitution of the classical PI controller of the speed control loop. This paper investigates the ANFIS as an open-loop speed estimator instead. The subtractive clustering technique was used as strategy for generating the membership functions for all the incoming signal inputs of ANFIS. This provided a better analysis of the training data set improving the comprehension of the estimator. Additionally the subtractive cluster technique allowed the training with experimental data corrupted by noise improving the estimator robustness. Simulations to evaluate the performance of the estimator considering the V / f and vector drive system were realized using the Matlab/Simulink ® software. Finally experimental results are presented to validate the ANFIS open loop estimator.

Current pulse fed high-pressure-sodium lamps

Spectral and photometric time-averaged measurements at nominal lamp power rating are presented for pulse operated HPS lamps of several manufacturers and different sodium concentrations. The choice of pulse and cycle parameters, which determine the optimal ratio between pulse and simmer powers are discussed. Spectra at various operating conditions as well as curves relating CCT, luminous flux and color rendering index with pulse cycle parameters are presented. Acoustic emissions were measured and are briefly discussed.

Tap-Off Power From the Overhead Shield Wires of an HV Transmission Line

In recent years, there was an increase of ancillary service loads, such as signaling systems, inspection robots, surveillance cameras, and other monitoring devices distributed along high-voltage transmission lines which require low-power dc voltage supplies. This paper investigates the use of the induced voltage in the shield wires of an overhead 525 kV transmission line as a primary power source. Since phase current variations throughout the day affect the induced voltage in the overhead ground wire, a step-down dc-dc converter is used after rectification of the ac voltage to provide a regulated dc output voltage. The initial encouraging results obtained indicate that this form of power supply can be a feasible and cost-effective alternative for feeding small ancillary service loads. The simulation results are validated by field measurements as well as the installation of a 200 W voltage stabilization system prototype.

Thyristor Controlled Rectifiers for Subway Substations

This paper presents the analysis of subway thyristor controlled rectifier substations. The classical analysis developed for 12 pulse diode bridges is adapted to consider thyristors and simulated. This simulation considers the simultaneous operation of several rectifiers connected to the same distribution network. Simulation results show that the harmonic impact of these rectifiers on the distribution network is considerable and is amplified by the cable capacitances. Measurements taken on a 12 pulse diode rectifier substation confirm this amplification effect

Design of a hybrid ballast with magnetic shunts: application to control of HID lamps

A procedure to design a lag ballast with magnetic shunts for HID lamps is proposed. A bidirectional semiconductor switch with phase angle control, connected in parallel to one of the ballast coils, acts on lamp power. The static switch control signal is provided by a power feedback loop that actuates on lamp current, compensating variations of the main voltage and/or lamp parameters. This system saves energy and extends lamp life. Measurements on a 70 W high-pressure sodium (HPS) lamp prototype ballast are presented. The dependence of the inductances on the magnetic circuit parameters is emphasized. Power factor and total harmonic distortion of line current are comparable to a conventional lag ballast.

Sound Emissions From Pulse Operated High-Pressure-Sodium Lamps

Current-pulse-fed high-pressure-sodium lamps generate audible noise even if lamp power frequency does not excite longitudinal acoustic resonance modes inside the arc tube. This noise is caused by magnetostriction in conductive parts of the arc tube-supporting frame and in the wires passing through the seal of the outer glass envelope. Conductor dimensional changes effectively couple mechanical energy to the jacket. Photoacoustic effects also cause noise due to pressure waves in a thin air layer surrounding the lamp. This paper investigates experimentally both phenomena and quantifies their contribution in order to minimize acoustic emissions.