Showing papers in "Canadian Electrical Engineering Journal in 1977"
TL;DR: A step-by-step procedure is developed in this paper to fully model an angle controlled CSIM drive, which includes such critical factors as commutation delay and the system equations are derived and cast in state-space form to employ advanced control techniques for the synthesis of stabilizers for CSIM drives.
Abstract: Current source inverter-fed induction motor drives (hereafter referred to as CSIM drives) have found wide application due to their reliable operation. They are unstable on open-loop operation over the normal speed-torque region. A step-by-step procedure is developed in this paper to fully model an angle controlled CSIM drive. The model includes such critical factors as commutation delay. The system equations are derived and cast in state-space form to employ advanced control techniques for the synthesis of stabilizers for CSIM drives.
18 citations
TL;DR: In this paper, it is shown that the numerical solution of electromagnetic scattering problems using moment methods can be carried out in a progressive manner by dividing the scattering surface into several small regions.
Abstract: It is shown that the numerical solution of electromagnetic scattering problems using moment methods can be carried out in a progressive manner by dividing the scattering surface into several small regions. The technique reduces the large matrix of the conventional moment method into several small matrices on the regions and enables one to solve easily the problem of scattering by very large objects. The accuracy of the method and the criteria for controlling computational errors are examined by its application to two-dimensional problems. Both parallel and perpendicular polarizations are assumed and the behaviour of the solutions for both smooth and singular field distributions on circular cylinders and prisms is studied. It is found that the surface distributions, such as induced currents, may be obtained more accurately by this method than the conventional moment method. The accuracy of the far fields, however, are generally of the same order for both methods. For convenience and brevity, the term PNM is used to refer to the method throughout this paper.
17 citations
TL;DR: An induction micro powered synchronous telemetry implant for myoelectric control of a powered prosthesis is described in technical detail and surgical implantation in a human, subsequent control of the prosthesis and future implications are discussed.
Abstract: An induction micro powered synchronous telemetry implant for myoelectric control of a powered prosthesis is described in technical detail. Surgical implantation in a human, subsequent control of a powered prosthesis and future implications are discussed.
12 citations
TL;DR: In this article, four synthetic rod insulators and two classical cap stem insulators were subjected to the simultaneous effects of freezing rain and high tension and the leakage current was shown as a function of the time elapsed before the radial thickness of ice accumulated on a pilot conductor reaches 1 3/4″.
Abstract: Four synthetic rod insulators and two classical cap stem insulators were subjected to the simultaneous effects of freezing rain and high tension. The thickness of ice on the insulators and the type of formation is measured at regular intervals. The leakage current is shown as a function of the time elapsed before the radial thickness of ice accumulated on a pilot conductor reaches 1 3/4″. This is the limit of ice load proposed for Hydro-Quebec's future 735 kV lines. With a view to cutting down on accumulation time in this first section of research programme on ice-covered insulators, the tests were performed at a temperature of − 10°C. The results show that the weight and thickness of accumulated ice are related to the geometry of the insulator. The leakage current increases with the thickness of ice accumulated. Because of the small distances between their skirts, the synthetic insulators favour the formation of lumps of ice which create considerable peaking in the discharge current, liable to cause flashover when the accumulation becomes considerable.
7 citations
TL;DR: In this paper, the effects of intermodulation noise in a satellite transponder were analyzed using an extension of a method which has been described previously and which is simpler to use than other methods in current use.
Abstract: Weak signals are suppressed and intermodulation noise is generated when a number of carriers having different amplitudes are amplified by a TWT. These effects are analyzed using an extension of a method which has been described previously2 and which is simpler to use than other methods in current use4,5,6,7. This paper describes the calculations and includes a comparison of the results with experimental observations. The results are useful in the design of a satellite communications system in which a TV signal and multiple radio or two-way voice signals are present in one satellite transponder. The calculations show that for each 1 dB signal suppression of the small carriers due to the presence of a large carrier at saturation, the suppression of intermodulation noise is by more than 2 dB. Based on these results, it would be advantageous to operate with a single carrier saturating the transponder when multiple unequal carriers are present.
6 citations
TL;DR: In this article, the results of a comparative study of digital modulation techniques for experimental work using the CTS system have been conducted in three phases, under contract to the Communications Research Centre, Ottawa.
Abstract: The Communications Technology Satellite (CTS), launched on 17 January, 1976 from Cape Canaveral, provides a very powerful and versatile vehicle for the experimental testing of new communications technology. The Communications Research Laboratory (CRL) of McMaster University has since 1972 been conducting a comparative study of digital modulation techniques for experimental work using the CTS system. This study which has been conducted in three phases, under contract to the Communications Research Centre, Ottawa is the subject of the present paper. The first phase consisted of the comparative evaluation by means of computer simulation of a variety of digital modulation techniques using a satellite type of channel. The results of this show that the best performance in terms of digital error-rate as a function of signal to noise ratio is obtained using the so-called fast-frequency shift keying (FFSK) modulation type. The second phase of the study consisted of the design and construction of a fast frequency-shift keying modem (modulator/demodulator) at a nominal data rate of 60 Mbits/sec. The details of this design and the results of preliminary testing of the modem are presented in the paper, and show that when the modulator and demodulator are operating back-to-back there is a performance degradation from theoretical of 1 dB in signal to noise ratio at a bit error-rate of 10−4. The third phase of the study consisted of the detailed laboratory testing of the modem under a variety of channel conditions preparatory to actual satellite testing. Some of the results of this testing are presented in the paper, and indicate that the FFSK is a very viable modulation type for use in high rate data communications via satellite.
6 citations
TL;DR: It is shown that in addition to speech interpolation, substantial savings can be achieved through the use of redundancy-reducing transcoding schemes, one for voiced and one for unvoiced sounds.
Abstract: This paper focuses on the efficient transmission of digital telephone-quality speech in a multichannel situation. It is shown that in addition to speech interpolation, substantial savings can be achieved through the use of redundancy-reducing transcoding schemes, one for voiced and one for unvoiced sounds. Specific waveform properties and coding schemes for both types of sounds, as well as the means for the discrimination, are discussed. The performance of two experimental systems which, respectively, triple and quadruple digital carrier capacity are presented.
4 citations
TL;DR: By developing a Pseudo Error Region (PER), the on-line error rate can be estimated much more rapidly without distrubing the data.
Abstract: This paper deals with the problem of monitoring the performance of digital communication links, with the objective of detecting the on-line signal failures as rapidly as possible. The problem of monitoring the performance of data communication links is inherent to data transmission. This paper describes a method of generating a measurable pseudoerror that can be used in a variety of applications. Some of the theoretical ideas of this technique were taken from Ref. 1. By developing a Pseudo Error Region (PER), the on-line error rate can be estimated much more rapidly without distrubing the data. The design of hardware and measurement results are presented, along with a comparison with theoretical predictions.
4 citations
TL;DR: The measured performance of a binary PSK and a Fast PSK modem are presented, compared, and discussed and modem lock-up times are presented for the Fast FSK modem.
Abstract: The measured performance of a binary PSK and a Fast PSK modem are presented, compared, and discussed. The modem tests were performed at 16 Kbps, a rate suitable for delta modulation and tactical satellite communications voice service. The performance of the modems was examined when they were in turn subjected to wide-band gaussian noise, channel band restriction, adjacent channel interference, co-channel interference, and finally impulsive noise. Modem lock-up times are presented for the Fast FSK modem.
3 citations
TL;DR: A brief review of the current state of research in the field of fusion is presented in this paper, where predictions being made as to when fusion might become a commercial reality as an energy source are discussed and an attempt is made to put the differing predictions into better perspective.
Abstract: A brief review of the current state of research in the field of fusion is presented. The predictions being made as to when fusion might become a commercial reality as an energy source are discussed and an attempt is made to put the differing predictions into better perspective. It is pointed out that there is a lack of research on the question of how the fusion energy is to be converted to useful forms of energy. It is mainly the failure to deal with this matter that is producing the wide ranges of predictions to be found in the literature.
2 citations
Abstract: This report gives some particular characteristics of the synthetic test circuit of the High-Power Laboratory of IREQ (Hydro-Québec). This circuit will make possible a multiplication of the testing power of the station when applied to circuit breakers and surge diverters.
TL;DR: In this article, the effect of the time constants of the regulators and the exciter circuits on the performance of a nonlinear power system was investigated. And it was concluded that the effective method of obtaining a markedly improved dynamic response is the optimal control of input power.
Abstract: Non-linear power system optimization studies commonly deal with optimal control of field excitation only and neglect the effect of regulator time constants and the presence of feedback loops. Studies reported in this paper show that the time constants of the regulators and the exciter circuits render the control of the field excitation less effective in obtaining an improved optimal response and that the closed loop operation provides only a limited improvement. Optimization studies of a power system simulated to different degrees of sophistication are described here. From these studies it is concluded that the effective method of obtaining a markedly improved dynamic response is the optimal control of input power. The desired level of improvement in system response can be obtained despite the governor loop time lag, particularly in systems incorporating doubly excited synchronous machine.
TL;DR: In this paper, the flux distribution in a two-dimensional ferromagnetic structure is obtained by a finite-difference technique, where the quasi-Poissonian partial differential equation describing the magnetic vector potential is transformed into a set of partial difference equations which are solved by a successive line-overrelaxation scheme.
Abstract: The flux distribution in a two-dimensional ferromagnetic structure is obtained by a finite-difference technique. The quasi-Poissonian partial differential equation describing the magnetic vector potential is transformed into a set of partial difference equations which are solved by a successive line-overrelaxation scheme. The numerical procedure converged quite well even under high saturation levels of the ferromagnetic material.
TL;DR: In this article, a nouveau circuit conçu pour effectuer des essais de fonctionnement sur des parafoudres limiteurs de courant utilisés dans les réseaux à Haute Tension.
Abstract: Cette publication présente un nouveau circuit conçu pour effectuer des essais de fonctionnement sur des parafoudres limiteurs de courant utilisés dans les réseaux à Haute Tension. Les résultats analytiques obtenus à date ont démontré que ce circuit est acceptable et très économique et qu'il présentera l'avantage unique de pouvoir effectuer des essais de fonctionnement sur des parafoudres complets à Haute Tension.
TL;DR: An overview of Datapac is presented including network structure, subscriber services, switching equipment, network performance, and network control.
Abstract: Datapac is a nation-wide public packet-switched data communications network operated by the Trans-Canada Telephone System. All communications over Datapac require the establishment of a virtual circuit between subscriber terminals. In order to accommodate applications where throughput is critical without penalizing applications where response-time is critical, the most appropriate of two delivery priorities may be specified for each virtual circuit. Datapac initially supports simple asynchronous interactive terminals as well as packet-mode terminals. The packet-mode interface conforms to the international standard CCITT Recommendation X.25. This paper presents an overview of Datapac including network structure, subscriber services, switching equipment, network performance, and network control.
TL;DR: In this article, a simplified model for obtaining a.c. resistance is proposed in the form of a solution algorithm, which is checked against direct experimental measurements and indicate satisfactory agreement, especially the difficulties associated with analyzing electrical performance.
Abstract: This paper critically examines various aspects of the performance of single layer ACSR, especially the difficulties associated with analyzing electrical performance. A simplified model for obtaining a.c. resistance is proposed in the form of a solution algorithm. Computed results are checked against direct experimental measurements and indicate satisfactory agreement.
TL;DR: An efficient and accurate method of simulating network changes such as outage or switch-in of transformers or lines which may be necessary both at the planning stage and in connection with operation of power systems is presented.
Abstract: This paper presents an efficient and accurate method of simulating network changes such as outage or switch-in of transformers or lines which may be necessary both at the planning stage and in connection with operation of power systems. The method involves sensitivity analysis around a base case state. Network changes are simulated subject to the condition of meeting scheduled demands of end buses of either the outaged elements or switched-in elements. The proposed technique has been applied to a medium size utility system and to the AEP standard test system with 118 buses. Simulation errors and execution times by the proposed method are compared with those of the standard Newton-Raphson method.
TL;DR: Some statistical properties of the main unvoiced phonemes are given along with three compact transcoding schemes for bit-rate reduction of unvoicing speech segments in multichannel PCM telephony.
Abstract: Some statistical properties of the main unvoiced phonemes are given along with three compact transcoding schemes for bit-rate reduction of unvoiced speech segments in multichannel PCM telephony.