Improving the reliability of semiconductor converters for supplying electric drives of exhausters

This article analyzes the existing methods of increasing reliability through multiple overstatement of the installed power of electric equipment according to the criterion of minimum total yearly costs. The proposed method of optimization of power circuits of semiconductor converters includes stages of choosing the configuration of power circuits on the basis of the limit of semiconductor switches and choosing the optimal number of phases and redundant units. The distinguishing characteristic of the method is the criterion used, namely, the probability of failure-free operation. This new method reduces the cost of installed power of a semiconductor converter compared to the known synthetic method on the level of total annual costs. It is shown that this method has some degree of flexibility; e.g., the development of the element base can be considered on the basis of the corresponding coefficients that depend on the operating temperature of power semiconductor valves. The proposed method can be successfully used in the design of semiconductor converters for supplying powerful electric drives, where, in the general case, the number of phases of a power circuit is not three. In this case, multiphase windings of an electric machine are connected according to a scheme with potential phase separation, which can be considered as an equivalent multiple redundancy system.     

Improving the energy efficiency of electric drives of reciprocating rolling mills

Components of power losses in electric drives of reciprocating rolling mills with an extremely irregular load diagram are considered. Energy efficiency is increased in the electric drive of reciprocating rolling blocks by improving electric drive components, methods, and control systems. It is confirmed that there is a high level of efficiency of the proportional control of the armature and excitation currents in the low loading area. The capabilities of both traditional systems of slave regulation and fundamentally new systems of the ac electric drive are analyzed. The nature of the benefits related to use of an electric drive with a field-regulated reluctance machine is explained—use of the whole of the armature winding coils during creation of electromagnetic torque and lack of a number of nodes with large current (compensating winding, auxiliary pole and excitation winding).     

Improving asynchronous electric drives of machines with a periodically varying load

A method of active influence on electric and mechanical transient processes during the operation of machines is proposed. The influence, which is performed by varying key parameters of the main electric drive, allows for the extension of the useful operating life and a reduction in the energy consumption of machines with periodically varying loads. A specific application of this method is shown, using as an example machines with cyclic impact loads and machines with pulsating loads.     

Improving response in control of adjustable electric drives of mechanisms with elastic links

A new method of combining control and regulation in order to improve the response of electromechanical systems with elastic mechanisms is proposed. Analytical dependences for the adjustment of regulators are derived elastic oscillation dampening taken into account. A solution to the problem of searching for achievable levels of physical (amplitude) limitations is proposed.     

Experience in introducing automation equipment for electric drives and industrial systems into the educational process

The use of industrial facilities for educational purposes is considered. Original solutions implemented in the design and construction of laboratory installations at the Department of Electrical Drives and the Automation of Industrial Installations of the Ural State Technical University Ural Polytechnical Institute (USTU-UPI) are described.     

Asynchronous electric motors for variable-frequency electric drives of drilling rigs

Operation peculiarities of the main drilling rig mechanisms are considered. The key specification requirements to asynchronous variable-frequency electric motors of the main drives are presented. The possibility of designing and developing the batch production of competitive, domestically produced drilling electric motors at enterprises of RUSELPROM concern is grounded.     

Increasing the reliability of electric networks

A review of Russian and American periodicals on the reliability of electric networks is carried out. New measures to increase the reliability of electric power supply of consumers are described.     

Multilevel converters for large electric drives

This paper presents transformerless multilevel power converters as an application for high-power and/or high-voltage electric motor drives. Multilevel converters: (1) can generate near-sinusoidal voltages with only fundamental frequency switching; (2) have almost no electromagnetic interference or common-mode voltage; and (3) are suitable for large voltampere-rated motor drives and high voltages. The cascade inverter is a natural fit for large automotive all-electric drives because it uses several levels of DC voltage sources, which would be available from batteries or fuel cells. The back-to-back diode-clamped converter is ideal where a source of AC voltage is available, such as in a hybrid electric vehicle. Simulation and experimental results show the superiority of these two converters over two-level pulsewidth-modulation-based drives     

SPICE-assisted simulation of controlled electric drives: anapplication to switched reluctance drives

An example of simulation of a closed loop controlled electric device that shows the feasibility of simulating the equipment by means of a general-purpose electronic circuit analysis program is described. The SPICE program was used because of its well-known facilities for simulating electronic circuits. A method for extending the SPICE facilities to simulate the electromechanical energy conversion and the drive control is reported. The simulation of a switched reluctance motor drive with closed loop speed control is considered, and the results were validated by experimental tests executed on an industrial drive     

Modelling of induction machines for electric drives

The author presents several linear and nonlinear models suitable for transient and steady-state analyses of induction machine drives. The models are presented in equivalent circuit form to preserve the identity of nonlinear parameters. The circuits, designated as Γ or inverse Γ form, are simpler than the conventional T-form circuit. Their parameters are readily determined from terminal measurements. The major effects of magnetic nonlinearity are included in the models in a way that is more accurate than that usually obtained with the conventional T-form circuits. Modeling of time harmonics is also discussed     

High-speed electric drives: technology and opportunity

This article provides background on the development and installation of high-speed electric motors (induction and synchronous) and controllers. There are compelling reasons for electric drives to be considered for applications that would conventionally be driven by steam turbines, gas turbines, and engines or motors with speed-increasing gearboxes. Electric drives offer an opportunity for efficient use of natural resources, clean and (comparatively) quiet power conversion, improved process control, and very attractive life-cycle cost. High-speed electric drives utilize technology (including variable speed control) to meet the needs of a rapidly changing industrial world. The high-speed electric drive provides another valuable option for consideration by the gas pipeline owner. This option needs to be considered as part of initial strategic planning. The electric option offers many “system” benefits for pipeline owners. It represents proven technology, and significant potential opportunity     

High-voltage autotransformer frequency converters for electric drives

The application of autotransformers in high-voltage ac electric drives with transistor frequency converters is considered. Circuit designs based on independent inverters of lower voltage, which are intended for increasing the power of electric drives, are demonstrated.     

Noise characteristics of electric motors of variable-frequency geared electric drives for elevators

The possibilities of improving noise characteristics of geared drives with single-speed asynchronous electric motors and variable speed of rotations are considered.     

Variable-frequency synchronous motor drives for electric vehicles

The performance capability envelope of a variable-frequency, permanent-magnet synchronous motor drive with field weakening is dependent upon the product of maximum current and direct-axis inductance. To obtain a performance characteristic suitable for a typical electric vehicle drive, in which short-term increase of current is applied, it is necessary to design an optimum value of direct-axis inductance. The paper presents an analysis of a hybrid motor design which uses a two-part rotor construction comprising a surface-magnet part and an axially laminated reluctance part. This arrangement combines the properties of all other types of synchronous motor and offers a greater choice of design variables. It is shown that the desired form of performance may be achieved when the high-inductance axis of the reluctance part is arranged to lead the magnet axis by 90° (elec.)     

Control systems of auxiliary electric drives in streetcars

Modernization methods are proposed for the auxiliary electrical equipment of streetcars, specifically for brake gears and door operators, that provide the desired parameters with the optimum use of resources allocated for control objectives. Design and schematic solutions for the electromechanical and semiconductor converter are also proposed.     

The calculation of stepper and synchronous electric motors for automobile electric drives

Peculiarities of calculations for electric motors for automobile electric drives integrated with electronic controls are considered.     

Improving the reliability of transformer gas-in-oil diagnosis

Dissolved gas analysis (DGA) is widely used to detect incipient faults in oil-filled electrical equipment. There is always some degree of inaccuracy in laboratory dissolved-gas measurements, especially at low gas concentrations, which affects gas ratios and other diagnostic calculations. This paper examines the measurement inaccuracy problem in detail using recent CIGRE data. It shows how proper allowance for this inaccuracy can improve transformer condition assessment and diagnosis by DGA.     

Electromagnetic gate-inductor electric drives with open-loop control systems

A simplified transducer-free realization of electromagnetic gate-inductor electric drives with openloop control systems is proposed with prospective applications for the majority of rotary-, linear-, and alternatemotion-type industrial mechanisms. A functional scheme of the control system for the electric drive under consideration is given. A simplified calculation of the basic parameters of the rotary motion electric drive is presented. The advantages of reducer-free electric drive constructions are shown.     

进一步深化电力可靠性管理工作

可靠性分析与预测能力为发电厂竞价上网,机组状态检修提供了良好的技术支持。电力可靠性管理工作是综合了安全管理与质量管理全过程的综合性的系统工程,因此,确定从事电力可靠性管理工作的人选和建立该项工作的组织保证体系至关重要。     

Improving the drives of gearless winches with high-torque induction motors

The drive efficiency in a gearless winch with high-torque induction motors may be increased by switching to a smaller-diameter tractional pulley and increasing the multiplication factor, as established by calculations for new induction-motor designs and confirmed by tests of prototypes.