James Patrick Lyons

The auxiliary quasi-resonant DC link inverter

A quasi-resonant DC link converter topology is proposed. The basic topology of the auxiliary quasi-resonant DC link (AQRDCL) is derived from the auxiliary resonant commutated pole (ARCP) converter and is closely related to the active clamped resonant DC link (ACRDCL) circuit. The operation and gating control strategy of the AQRDCL converter, which ensures zero voltage switching of all inverter switches and zero current switching of the auxiliary switches, is presented. The proposed circuit utilizes auxiliary switches to trigger the LC resonance of the DC link to create a zero voltage switching opportunity for the inverter switches. The waveform quality and the performance of the AQRDCL inverter, which has PWM capability, is compared with the DPM strategy of the ACRDCL inverter.<<ETX>>

Control of three phase power supplies for ultra low THD

Current regulators are proposed and investigated for high-power three-phase power supplies with ultra-low total harmonic distortion (THD) (less than 0.5%). Two valid approaches to realize three-phase power supplies can be proposed. In the first approach, current regulated pulse-width-modulated (PWM) inverters along with high bandwidth voltage control loops are proposed. In the second approach, an internal voltage synthesizer under closed loop current control is used. Both approaches have mechanisms to decouple the LC filter interactions and to lower the THD. The tradeoffs of these two basic approaches are investigated. The influence of different current regulators in case of the current-regulated PWM (CRPWM) converter is investigated as well as different approaches to control the voltage synthesizer under current control. The study compares the effectiveness of these current regulator in soft-switching PWM inverters and describes a method to measure accurately ultra-low THDs.<<ETX>>

Innovation IGCT main drives

The paper introduces the new IGCT drives which feature three-level NPC full regenerative power converters-the initial 3300 V product is rated up to 10 MVA. The drives utilize IGCT devices-new hard driven GTOs achieving unprecedented switching performance and effective PWM carrier frequencies up to 1 kHz. The converters use diodes formulated for soft recovery and efficient clamp snubbers to allow commutation of up to 4000 A. Under development is a 6600 V drive employing series connected IGCT elements to achieve up to a 20 MVA rating. These high performance drives, targeted at heavy-duty rolling mill applications, employ a DSP based three-level space vector modulation algorithm with active charge balance neutral point control. The drive system includes a high bandwidth feed forward synchronous motor control algorithm achieving unprecedented torque performance at these power levels. The PWM load converter is capable of achieving output frequencies up to 75 Hz. A mill resonance compensation algorithm has been developed to take advantage of the available torque response for mill stand control. The IGCT PWM source converter technology eliminates the need for the expensive VAr compensation and harmonic filtering required by cycloconverter main drives. The source converter controls feature synchronous reference frame current regulators that maintain a nominal unity power factor grid interface. The controls offer the opportunity to fix mill power quality issues by adding features such as VAr compensation, harmonic optimization, active damping of grid resonances, and flicker control.

Integration of Magnetic Bearings in the Design of Advanced Gas Turbine Engines

Active magnetic bearings provide revolutionary advantages for gas turbine engine rotor support. These advantages include tremendously improved vibration and stability characteristics, reduced power loss, improved reliability, fault-tolerance, and greatly extended bearing service life. The marriage of these advantages with innovative structural network design and advanced materials utilization will permit major increases in thrust to weight performance and structural efficiency for future gas turbine engines.However, obtaining the maximum payoff requires two key ingredients. The first key ingredient is the use of modern magnetic bearing technologies such as innovative digital control techniques, high-density power electronics, high-density magnetic actuators, fault-tolerant system architecture, and electronic (sensorless) position estimation. This paper describes these technologies and the test hardware currently in place for verifying the performance of advanced magnetic actuators, power electronics and digital controls. The second key ingredient is to go beyond the simple replacement of rolling element bearings with magnetic bearings by incorporating magnetic bearings as an integral part of the overall engine design. This is analogous to the proper approach to designing with composites, whereby the designer tailors the geometry and load carrying function of the structural system or component for the composite instead of simply substituting composites in a design originally intended for metal material. This paper describes methodologies for the design integration of magnetic bearings in gas turbine engines.Copyright