scispace - formally typeset
Search or ask a question
Author

Fred G. Turnbull

Bio: Fred G. Turnbull is an academic researcher from General Electric. The author has contributed to research in topics: AC motor & Inverter. The author has an hindex of 13, co-authored 22 publications receiving 500 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this article, a trade-off study was performed for many transistor and thyristor circuits and configurations and the weighting criteria included full and part load efficiency, size, weight, reliability, ease of control, injected harmonics, reactive power requirements, and parts cost.
Abstract: An investigation into power conditioners that interface with photovoltaic arrays and utilities has been recently completed. The ratings for this investigation include residential systems (5-30 kW) that interface with a 240-V single-phase utility connection and intermediate systems (30-200 kW) that interface with a 480-V three- phase utility connection. Both systems mandated that an isolation transformer be provided between the array and the utility interface. A trade-off study was performed for many transistor and thyristor circuits and configurations. The weighting criteria included full- and part-load efficiency, size, weight, reliability, ease of control, injected harmonics, reactive power requirements, and parts cost. As the result of this study, a 10-kW high-frequency PWM transistor inverter feeding a high-frequency isolation transformer with a sinusoidally shaped current wave was selected. The output of the transformer is rectified with a diode bridge rectifier. Four thyristors, used as 60-Hz switches, reverse the polarity of the rectified current on every other half-cycle of the utility voltage. This reversal is accomplished slightly before the natural zero crossing of the voltage, thereby providing commutation for the thyristors. The results in the intermediate rating study targeted on a 100-kW design using power transistors in a full-bridge circuit connected to a 60-Hz three-phase transformer. Three bridge circuits are provided to interface with the polyphase utility. The switching strategy for the power transistors is based on a sine wave shape of current with a controlled deadband.

71 citations

Journal ArticleDOI
TL;DR: In this paper, the state-variable formulation is applied to the analysis of two widely used drive systems incorporating square-wave inverters with 180° and 120° firing logic, and the results are compared to an analytical solution.
Abstract: The application of adjustable frequency static inverters to induction motor speed control has resulted in a diversity of inverter designs. In this paper, the state-variable formulation is applied to the analysis of two widely used drive systems incorporating square-wave inverters with 180° and 120° firing logic. Measured characteristics of an actual drive system are included, and the results are compared to an analytical solution. Steady-state speed-torque curves for each inverter supplying three markedly different types in induction motors are given. Performance of the two inverter drives are compared by a thorough investigation of typical operating points.

66 citations

Journal ArticleDOI
TL;DR: In this article, a load-commutated inverter consisting of two bridges connected in parallel is used to provide two-way power flow by reversing the dc current. But the control system described does not use shaft position sensing, but senses the motor terminal voltage and the ac line current to determine the motor internal operating conditions.
Abstract: Synchronous motor drives are beginning to enjoy renewed popularity for certain applications such as flywheel energy storage. One of the reasons is that a synchronous motor drive can be made self-commutating so that the inverter becomes equivalent to a conventional phase-control bridge converter without large commutating components. The drive to be controlled consists of an inductor alternator coupled to a flywheel that will be used for temporary energy storage. The flywheel speed will vary over a two-to-one range; thus full performance can be achieved using a load-commutated inverter. A simple auxiliary commutating circuit is provided only for initial starting. The drive must operate both from a fixed dc voltage source (battery) and from a variable dc voltage source (dc motor), as it is intended for use in a battery-powered vehicle for load leveling. The load-Commutated inverter consists of two bridges connected in parallel so as to provide two-way power flow by reversing the dc current. The control system described does not use shaft position sensing, but senses the motor terminal voltage and the ac line current to determine the motor Nare internal operating conditions. This control method maintains the silicon-controlled rectifier (SCR) turn-off time as a constant percentage of the period of the generated back electromotive force (EMF) as speed and current are varied during operation. The inverter turn-off time is thus maintained by feedback control rather than the use of special function generators. A 20-kVA laboratory development drive system has been built and successfully tested using this control strategy.

58 citations

Patent
22 Feb 1990
TL;DR: In this paper, a method and apparatus for controlling the switching devices in a switched reluctance machine bridge inverter having at least two switching devices per phase is presented. But the method is not suitable for the use of a flyback diode.
Abstract: A method and apparatus are provided for controlling the switching devices in a switched reluctance machine bridge inverter having at least two switching devices per phase. One switching device is used for hysteresis band current chopping to regulate phase current magnitude, while the other switching device, in combination with a flyback diode, provides a circulating path for phase current. Alternatively, current chopping and circulating are alternated between both switching devices during each conduction interval of the corresponding machine phase. Ripple current is decreased, thereby reducing the required size of the DC link capacitor. Switching losses are also reduced.

47 citations

Patent
05 Apr 1982
TL;DR: In this paper, a three-phase regenerative rectifier provides power flow from ac to dc using a three phase rectifier bridge, where a power transistor or field effect transistor is coupled in inverse parallel with each rectifier device to provide a path for current from the dc output of the rectifier back to the ac supply during regeneration.
Abstract: A three-phase regenerative rectifier provides power flow from ac to dc using a three-phase rectifier bridge. The reversal of the input ac voltage at the input frequency commutates current in the rectifier devices. A power transistor or field-effect transistor is coupled in inverse parallel with each rectifier device to provide a path for current from the dc output of the rectifier back to the ac supply during regeneration. The rectifier devices can be phase controlled thyristors or diodes. Control means sense the three-phase voltage and switch the transistors in phase with the ac supply. Commutation of the transistors is provided by their self-contained turn-off capabilities.

32 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this paper, power quality problems associated with distributed power (DP) inverters, implemented in large numbers onto the same distribution network, are investigated, and a complete network simulation study on an existing residential network with large penetration of photovoltaics (PV) on rooftops of houses and commercial buildings is included.
Abstract: Power quality problems associated with distributed power (DP) inverters, implemented in large numbers onto the same distribution network, are investigated. Currently, these power quality problems are mainly found in projects with large penetration of photovoltaics (PV) on rooftops of houses and commercial buildings. The main object of this paper is to analyze the observed phenomena of harmonic interference of large populations of these inverters and to compare the network interaction of different inverter topologies and control options. These power quality phenomenons are investigated by using extensive laboratory experiments, as well as computer modeling of different inverter topologies. A complete network simulation study on an existing residential network with large penetration of PVs, is included.

801 citations

Patent
16 Apr 1992
TL;DR: In this article, a surgical handpiece comprises a motor energizable for moving a tool member, electric energy supply actuable for energizing the motor and a manually actuable trigger actuable to control motor operation.
Abstract: A compact surgical handpiece comprises a motor energizable for moving a tool member, electric energy supply actuable for energizing the motor and a manually actuable trigger actuable to control motor operation. A motor control circuit interconnects the motor electric energy supply and trigger for running and braking the motor in response to actuation and release of the trigger. The control circuit includes a compact regulated voltage supply, a motor overcurrent limiting feature and a motor braking feature which is effective even if the operator fails to fully disconnect the electrical supply to the motor upon releasing the trigger.

697 citations

Journal ArticleDOI
Kenichi Iizuka1, Hideo Uzuhashi1, Minoru Kano1, Tsunehiro Endo1, Katsuo Mohri1 
TL;DR: In this article, the motor voltage is chopped by commutator transistors to change the motor speed, and the motor rotor position is determined by the back electromotive force induced in the stator windings.
Abstract: The microcomputer control of a brushless motor without a shaft position sensor is studied. A method which permits the determination of the permanent magnet rotor position by the back electromotive force (EMF) induced in the stator windings and the starting technique which uses the motor as a synchronous motor at standstill are explained. The motor voltage is chopped by commutator transistors to change the motor speed. The control system consists of a 4-b single-chip microcomputer and two quad-comparators.

455 citations

Journal ArticleDOI
TL;DR: In this paper, a microcomputer-based control of a residential photovoltaic power conditioning system is described, which is responsible for array current feedback control, maximum power tracking control, array safe zone steering control, phase-locked reference wave synthesis, sequencing control, and some diagnostics.
Abstract: Microcomputer-based control of a residential photovoltaic power conditioning system is described. The microcomputer is responsible for array current feedback control, maximum power tracking control, array safe zone steering control, phase-locked reference wave synthesis, sequencing control, and some diagnostics. The control functions are implemented using Intel 8751 single-chip microcomputer-based hardware and software. The controller has been tested in the laboratory with the prototype power conditioner and shows excellent performance.

339 citations

Proceedings ArticleDOI
02 Oct 1994
TL;DR: In this paper, a position sensorless control scheme for a doubly excited induction machine is proposed, which uses only the rotor voltages and currents as the feedback signals, which substantially reduces the costs and enhances the reliability.
Abstract: A novel control strategy to realize decoupled control of torque and reactive power for a doubly excited induction machine using a position sensorless scheme is proposed. The critical issues related to the torque angle estimation and control for a doubly excited induction machine are discussed. Compared to the other position sensorless schemes for a doubly fed machine, the proposed control method uses only the rotor voltages and currents as the feedback signals, which substantially reduces the costs and enhances the reliability of the position sensorless control of a doubly fed AC machine. Computer simulation and experimental results are given to verify the position sensorless control scheme. >

317 citations