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Electric Power Applications, IEE Proceedings B

Issue 3 • Date May 1983

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Displaying Results 1 - 16 of 16
  • Digital computer simulation of variable-speed PWM inverter-machine drives

    Page(s): 149 - 160
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1709 KB)  

    It is predicted that, with the increasing availability of digital computing facilities, computer-aided design will play an increasingly important and cost-effective role in the design of variable-speed drives (VSD). The paper describes the detailed development of an extremely versatile PWM VSD package which has the potential for investigating a wide range of operational modes. The capabilities of the package are demonstrated, using a number of examples of typical operational modes of PWM inverter-machnine systems, which serve to highlight the potential use of the package. The validity and accuracy of the computer simulations are confirmed, using experimental results obtained from a microprocessor-controlled PWM inverter -drive system. View full abstract»

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  • Impedance and phase balancing of mains-frequency induction furnaces

    Page(s): 161 - 170
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (976 KB)  

    The impedance presented to the supply by coreless and channel induction furnaces used for melting and holding metals is not constant. Many such furnaces are designed for single-phase working and their power supplies often include components to enable a balanced load to be taken from a 3-phase system. Owing to the varying furnace impedance, such balancing components are designed to be variable and are often operated by the furnaceman. Variation in furnace impedance is largely due to the condition of the furnace-lining refractory for a given metal charge, and it is useful to the foundry user to monitor this condition by assessing changes in impedance. The basic action of the induction furnace and approximate formulas for the calculation of furnace impedance, together with methods of phase balancing, are described in an attempt to assist furnace users in monitoring the condition of their plant. Examples of calculation and the use of a furnace-condition diagram are given. However, the formulas used are intended to serve as a guide and by no means do they fully describe the complex electromagnetic conditions which exist, normally requiring solutions to magnetic-flux problems in three dimensions. View full abstract»

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  • Optimum design of a new DC-SC circuit

    Page(s): 171 - 180
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (980 KB)  

    Detailed analysis and optimum design of the commutating circuit of the recently proposed DC-side commutated current-source inverter are given. Analysis was performed for each topology mode during a step transition interval under certain assumptions and using various normalised quantities. Using the analysis results, optimum design of the commutating circuit was studied with an aim to maximising the turn-off time with a minimum commutating energy. Experimental results showed reasonably good agreement with the theoretical results. View full abstract»

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  • Energy-transfer mechanism and current waveforms of parametric transformers

    Page(s): 181 - 185
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (671 KB)  

    The paper presents a graphical approach to the description of the nonlinear and time-varying phenomena involved in the operation of a parametric transformer. A relationship between the mechanism by which energy is transferred through the transformer and the corresponding primary and secondary winding currents is established through the concept of a relative magnetisation characteristic. Current waveforms obtained by this approach are substantiated by waveforms measured on an experimental unit, and the concept is further extended to discuss the various protection properties inherent in a parametric transformer. View full abstract»

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  • Twin-armature rotary-linear induction motor

    Page(s): 186 - 192
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    The twin-armature, rotary-linear induction motor is one of several types of motors with two degrees of mechanical freedom. Its rotor can perform either separately or simultaneously linear and rotary motions. In the paper, the performance characteristics of the rotary-linear induction motor are presented. A theory is derived based on the Fourier-series method which takes into account the end effects of the twin motor's armatures. Results obtained from the calculations are compared with experimental measurements. View full abstract»

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  • Book review: Stepping Motors: a Guide to Modern Theory and Practice

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    Freely Available from IEEE
  • Microprocessor control of triac cycloconvertor

    Page(s): 193 - 200
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1014 KB)  

    On account of drive-system requirements, convertor performance and cost, it is becoming more and more desirable to replace the relatively complex control circuits of solid-state cycloconvertors by microprocessor-based controllers. A dedicated-microprocessor controller for triac cycloconvertors, making use of the MC6809 family of components, is described, which relies on software for timing and delay-angle computation as well as for convertor selection and blanking control. Provision for smooth transition in changing the output frequency and amplitude is included as an added feature. Descriptions of the hardware and software designs of the controller are given and experimental results are presented to illustrate the performance achieved. View full abstract»

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  • AC characteristics in AC/DC/DC conversion

    Page(s): 201 - 206
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (541 KB)  

    The use of line commutated static converters can cause significant problems in power-supply networks, owing to the reactive power and the harmonic components generated. Technological improvements in power transistors suggest that DC/DC convertors supplied by diode rectifiers could be applied more profitably than phase-controlled AC/DC convertors. This especially holds true for applications where inversion of the power flow is not required. The paper considers the AC characteristics of a double conversion system composed of a 3-phase bridge diode rectifier loaded by a PWM chopper. The relationships between the AC currents, chopper modulator parameters and pulse number of the AC/DC rectifier are investigated. The chopper operating conditions, which provide a balanced system of alternating currents are determined: consequently, an improvement in the overall power factor is obtained. View full abstract»

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  • Determination of optimum operating frequency of a current-source inverter-controlled asynchronous machine by measurement of stator voltages

    Page(s): 207 - 212
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (511 KB)  

    Theory and experimental results are given, concerning a control law for a current-fed asynchronous machine, defining frequency on the basis of the machine's stator voltages. This law means that the speed sensor is no longer essential; it also allows estimation of rotor-current frequency and, hence, the rotation speed: An experimental model shows that the system is stable and also demonstrates good performances in the steady-state condition. View full abstract»

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  • Calculation of arc-circuit asymmetry in electric-arc furnaces

    Page(s): 213 - 217
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    A method is described to determine the arc voltages on a per-phase basis of a 3-phase direct electricarc furnace. Having determined the arc voltages, other arc parameters, such as arc resistance, length and power, can then be obtained. By using the procedure outlined, in conjunction with experimental data on a 100 t, 5¿m diameter shell furnace having a triangulated secondary electrical system, it will be shown that controlling arc powers by means of the impedance control method still results in asymmetric furnace operation. Sample calculations are included, illustrating actual conditions for this furnace. View full abstract»

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  • Mathematical model and electric-circuit simulation of DC machines

    Page(s): 218 - 225
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1035 KB)  

    A general mathematical model of the DC machine is developed. This model accounts for magnetic saturation. The intrinsic nonlinearity of the set of differential equations is also taken into account. From this nonlinear mathematical model, which is highly parameterised, a general multiport model and its dual for electric-circuit simulation are presented. The dual model is suitable for system analysis. View full abstract»

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