Thyristor Frequency Converter Research Articles

Варианты систем электродвижения ледоколов мощностью 60 и 120 МВт

Variants of electric propulsion systems for powerful icebreakers with the use of transistor frequency converters or thyristor frequency converters with direct coupling (DFC) are considered. Rowing motors synchronous or asynchronous. With transistor converters, the semiconductor element base is mainly imported, with thyristor FCs, it is mainly domestic. But DFCs work with reactive power consumption, and its generation requires the use of additional devices, such as passive filters or STATCOMs. When the propellers of icebreakers are reversed, the energy of the propellers is recuperated. In electric propulsion system with transistorized FСs, resistors and choppers are used to absorb the regenerated energy. In electric propulsion system with DFC, it is possible to recuperate energy into the mains, and this allows you to reduce the power of the resistors. Resistors are included in STATCOMs, expanding their functions (reactive power generation, voltage filtering, energy absorption).

Calculating Overvoltages in Windings of Synchronous Motors with Thyristor Frequency Converters

Calculating Overvoltages in Windings of Synchronous Motors with Thyristor Frequency Converters

ПІДВИЩЕННЯ ЕНЕРГЕТИЧНОЇ ЕФЕКТИВНОСТІ ТРАНСПОРТУВАННЯ З УРАХУВАННЯМ ЗМІН ВАНТАЖОПОТОКУ З ОЧИСНОГО ЗАБОЮ

Purpose: to find a rational way to regulate the speed of the conveyor belt by the criterion of minimizing the total energy consumption for the operation of the belt conveyor. Methodology: Kariman’s S.A. - determination of specific transportation costs by using conveyor transport. Results: as a result of the obtained data smooth regulation of speed of a tape allows to reduce total energy consumption by 39%. To ensure this method it is necessary to develop complex control algorithms and implement thyristor frequency converters, and the cost of their installation is incomparably higher than the potential energy savings for transportation that they can provide. The use of three-speed discrete control, which is carried out by switching the number of pole pairs or changing the inductance of the motor windings. This method provides a high (up to 27%) reduction in total energy consumption. Increasing the number of operating speeds by more than three does not give a significant increase in additional savings. The difference in power consumption between three and four-speed adjustable drives is 2%. Scientific novelty: determining the most optimal method of regulation, according to the method of Kariman S.A., uses a model that calculates the power consumption in different modes of speed control using the software package "Matlab Simulink". Practical significance: the developed program allows determining the parameters of belt speed control for the whole chain of conveyors taking into account the alternating cargo flow from the treatment face in order to reduce the specific energy consumption for transportation

Energy-efficient thyristor frequency converter with relay-frequency energy regulation for induction furnace

Here we investigate induction furnace electrical parameters with lump loading changeable liquid melt level in the melting pot, and frequency converter with advanced energy data, with hybrid control of electrical reset mode with frequency controlling and frequency converter reconfiguration in conditions of profoundly changing loads.

A Combined Frequency Converter for Soft Acceleration of Induction Electric Drives with Heavy Starting Conditions

The usability of a thyristor frequency converter with a supplementary controlled series compensator for soft starting of induction motors with high torque of inertia of actuating mechanisms is considered as an alternative to transistor converters. It is shown that the supplemental device, in the form of a transistor–capacitor convertor, can be considered as an adjustable capacitor, the equivalent capacitance of which can be varied from very large values (to a maximum of infinitely large) to some fixed minimum value. The voltage of an adjustable series capacitor provides the desired switching conditions of thyristor inverter, and the capacitive reactance ensures the compensation of reactive power consumed by the induction motor and thyristor inverter, reducing the current load of the motor and converter. The addition of a thyristor current converter with a controlled series compensator of reactive power in the form of a transistor–capacitor unit makes it possible to carry out a soft start of induction motors similar to the starting modes of synchronous machines. Simulation results confirming the achievement of the desired effect are presented. It is shown that the supplemental device in the form of transistor–capacitor converter is a robust system well adaptable to various conditions of electric-drive operation. The functional equivalence of a transistor frequency converter and thyristor frequency converter with a supplemental transistor–capacitor unit with a substantially lower cost of the latter makes possible a new mechanism for soft starting of powerful electric drives with induction motors under conditions of high torques of inertia of actuating mechanisms.

Analysis of a Doubly Fed Induction Motor in Electric Drives of Pumping Stations

The investigation of a doubly fed induction motor in electric drives of pumping stations is conducted in this paper. The effect of non-sinusoidal rotor supply is considered in the analysis as well. The current total harmonic distortion (THD) is evaluated with respect to the selected voltage modulation in a thyristor frequency converter (TFC) as well as on motor duty cycle. A novel method of reactive power regulation with constant rotor current I2=I2н=constant is proposed. It is shown that the proposed method considerably improves motor performance in the whole operation range. The proposed analytical method is verified with laboratory measurements.

A combined method of simulation of an electric circuit and field problems in the theory of induction heating

A combined method for numerical computation of the electromagnetic field in induction-heating systems is proposed and used. The method consists in a combination of methods of integral equations for the computation of the electromagnetic field in the area outside the load and methods of finite elements or finite differences for the computation of the electromagnetic field inside the load. A method of simulation of electrotechnical systems with simultaneous solving of circuit and field problems is proposed based on this method. Using the example of induction-heating devices, an external problem associated with the computation of circuit inductors, power supplies, and balancing capacitors and an internal problem related to the computation of the electromagnetic field and internal heat sources inside the load are formulated. The simulation of induction heaters is considered taking into account features of thyristor frequency converters with a parallel inverter.

Compensator of a multiphase inductive crucible furnace

A method is proposed for calculating the compensator of a multisection inductive crucible furnace, to which power is supplied by means of a single-phase thyristor frequency converter. The results of computer simulation and physical modeling of a multiphase inductor with compensators are compared.

Facilities for ice melting on electric transmission lines

Methods of ice melting on electric transmission lines using diode and thyristor rectifiers are considered. To shorten the melting time of ice and to simplify the commutation circuit at substations, it is suggested to use multipole converters based on thyristor frequency converters with a direct connection.

Control of electromagnetic stirring by power focusing in large induction crucible furnaces

An approach is proposed for the calculation of the operating conditions of an induction crucible furnace at the final stage of melting with the power focused in various regions of melted metal. The calculation is performed using a model based on the method of detailed magnetic equivalent circuits. The combination of the furnace and a thyristor frequency converter is taken into account in modeling.

Developments of OAO All-Russian Research and Design Institute of Relay Manufacture with a Pilot Factory of ABS electro in field of high-voltage electric drive and power electronics

The main developments of OAO All-Russian Research and Design Institute of Relay Manufacture with a Pilot Factory in the field of high-voltage electric drives and semiconductor converters designed and fabricated at the institute are considered. The key products are different types of thyristor devices for a soft startup based on thyristor frequency converters and thyristor devices for the automated actuation of a reserve in the power industry.

Assuring continuous input current using a smoothing reactor in a thyristor frequency converter for induction metal melting and heating applications

The approximate analysis of a thyristor frequency converter for induction heating and melting is described. The method for calculating the smoothing reactor inductance, which will provide the continuous mode of inverter input current operation, is proposed. The laboratory prototype of the above converter has been made and examined. The results of the experiments are in good agreement with the theoretical calculations.

Medium frequency combined inverter for electroheat with improved starting

Current-fed parallel inverters used for induction heating sometimes fail to start. Simulation and measurements show the importance of the turn-off angle during start up. An auxiliary voltage-fed inverter operated in parallel with the main current-fed inverter obviates the difficulty and provides reliable starting behaviour. On the basis of the results a new model of the thyristor frequency converter (160 kW, 4.0 kHz) has been projected for industrial induction heating and melting applications.

Energy-saving methods for regulating parameters of centrigual pumps

Instances of parameter invariability (delivery and head) are rather infrequent during centrifugal pump operation. As a rule, the pump should provide for delivery within a certain range of values for which regulation must be employed. For a number of reasons, it is frequently necessary to vary the parameters in the pump system--for example, decrease the delivery. This regulation of pump parameters can be accomplished by different methods with substantially different energy demands: by using a bypass, a gate valve, undercutting of the rotor in terms of outside diameter, and by varying the rotation frequency of the pump's shaft. The energy savings may be extremely large on varying the speed of the pump's shaft, especially when the range of regulation in terms of delivery is increased. Experience has shown that despite the high cost of speed regulators, their use is more economical. There are several methods of regulating the rotation frequency of pump drives. Among them are variable belt drives, hydrodynamic speed regulators, AC electric motors and thyristor frequency converters. The article gives the advantages and disadvantages of each method.

Gearless Drive for a Finish-Grind Mill with a Capacity of 160 t/h

The principle of the gearless drive has already been applied to some large mills. A synchronous motor is ``wrapped'' directly around the mill cylinder and supplied by a thyristor frequency converter at approximately 10-percent system frequency. The drive thus operates at the low mill speed and dispenses with interposed gearing.

Starting of Large Synchronous Motor Using Static Frequency Converter

This paper deals with the synchronous starting of a large synchronous motor, using a static thyristor frequency converter system. This method, in the following called, Converter Starting, is described. Special inverter questions are treated and the results of analytical and computer studies of the system and of a field test are presented. Potential applications of the method are dewatered starting in the pumping mode of reversible pumped-storage generator/motors and the starting of large synchronous condensers. The same equipment can also be used for braking the machines.