RU2161362C1 - Voltage divider - Google Patents

Abstract

FIELD: electrical engineering including semiconductor engineering. SUBSTANCE: voltage divider has converter transformer with sectionalized secondary winding. Anodes of thyristors 1, 2 and cathodes of thyristors 3, 4 are differentially connected to extreme leads of sectionalized secondary winding. One lead of load 6 is connected to cathode of thyristor 1 and to anode of thyristor 3 and its other lead, to midpoint of sectionalized winding. One lead of load 7 is connected to cathode of thyristor 2 and to anode of thyristor 4 and its other lead, to midpoint of sectionalized winding. RMS value of supply voltage is U₁ at frequency f₂ across loads 6, 7. EFFECT: improved harmonic composition of output voltage. 2 dwg

Description

 The invention relates to electrical engineering, in particular to semiconductor technology, and can be used to reduce the frequency of the operating voltage on two groups of electric motors and on other consumers of electricity.

 Known frequency converters, which are used to reduce the voltage frequency by 3 times at power receivers in comparison with the frequency of the alternating voltage at the input of the converter.

 However, such converters have a low power factor due to inefficient use of voltage at the input of the converter, due to non-linear distortions of the current and voltage at the input and output of the converter [a. with. USSR N 1554089, class H 02 M 5/27, 1990; Rutshtein A.M. Adjustable fan drive // Lokomotiv, 1998, N 6, c. 23-24].

Known frequency divider [a.s. USSR N 639109, class H 02 M 5/27, 1978] containing a rectifier bridge on thyristors. To the connections of the anodes of the thyristors and the cathodes of the thyristors an alternating voltage U _{1 with a} frequency of f ₁ is supplied. A load is connected to the connections of the anodes and cathodes of the thyristor rectifier bridge, the voltage at which U ₂ with a frequency of f ₂ = f _1/2 .

 The disadvantage of this device is the loading of an AC energy source of constant current component and even harmonic current components, low power factor due to inefficient use of voltage at the input of the converter.

 Also known is the direct frequency converter of single-phase-single-phase voltage (prototype) [Kurbasov A.S., Feoktistov V.P. A new voltage converter circuit // Lokomotiv, 1997, N 5, c. 28-29]. The converter is made on four thyristor keys, each of which contains two counter-parallel connected thyristors. One output of the energy source is connected to the output of the first pair of thyristor keys, and the other output of the energy source is connected to the output of the second pair of thyristor keys. One load terminal is connected to the output of one thyristor switch of the first and second pair, and the other load terminal is connected to the output of other thyristor switch of the first and second pair.

 The disadvantages of the frequency converter is the low quality of the output voltage and the complexity of the device.

 The aim of the invention is to improve the harmonic composition of the output voltage, increase the reliability of the device and improve the power factor.

 The goal is achieved in that each extreme terminal of the partitioned secondary winding of the transformer is connected to one anode and cathode of the divider thyristors.

Two-section load sections are connected to the midpoint of the sectioned winding and other anodes and cathodes of thyristors connected to the extreme leads of the sectioned winding of the transformer. This connection of the elements of the voltage divider provides a simultaneous decrease in the effective voltage value from U ₁ to U ₂ and the frequency from f ₁ to f ₂ = f _1/2 in two load sections.

 Thus, the claimed voltage divider meets the criteria of the invention of "novelty."

Known frequency converters in which the effective voltage is controlled by modulation at a high frequency or synchronous pulse modulation at the fundamental frequency, by a phase method or by a change in the effective alternating voltage supplied to the converter, are characterized by non-linear distortions of the current, voltage at the input and output of the converter, and the possibility of short circuits of the energy source thyristors of the converter and a decrease in power factor. In the proposed technical solution, due to the distribution of voltage into two load sections, a step-sinusoidal form of voltage at the output is provided with an effective voltage U ₂ <U _{1 of} frequency f ₂ = f _1/2 , thyristor switching is natural with the exception of the possibility of short circuits in the device, and with shifting the work of the load sections in time by an angle of 180 ^o increases the power factor of the divider.

 Thus, the claimed voltage divider meets the criteria of the invention "significant differences".

 The invention is illustrated in FIG. 1-2.

 In FIG. 1 is a circuit diagram of a voltage divider of increased reliability that improves the harmonic composition of the output voltage and power factor.

Thyristors 1, 2 are connected by the anode, and thyristors 3, 4 are connected by the cathode to the extreme terminals of the transformer sectional winding 5. The voltage U _{1 of} frequency f ₁ is supplied to the primary winding of the transformer. The two-section load 6, 7 is connected by one terminal to the midpoint of the transformer sectioned winding. By another conclusion, the load section 6 is connected to the cathode of thyristor 1 and to the anode of thyristor 3, and the load section 7 is connected to the cathode of thyristor 2 and to the anode of thyristor 4.

 The principle of controlling the thyristors of the voltage divider is the same as in all known methods of controlling modulation at a low frequency with a thyristor control angle α = 0. The known system for generating thyristor control pulses contains a trigger that allows you to divide the voltage frequency into two and a thyristor control pulse shaper 1, 2 , 3, 4 at the moment of transition by alternating voltage through zero in accordance with the control algorithm.

Timing diagrams of voltages U _{1 with} frequency f ₁ and voltages U ₂ at loads 6, 7 with frequency f _{2 are} shown in FIG. 2.

The numbers 1, 2, 3, 4 correspond to the numbers of the thyristors in FIG. 1, which are in a conducting state for a half period of alternating voltage. The distribution of the supply voltage U ₁ over the partitioned loads to the value U ₂ while reducing the frequency from f ₁ to f ₂ is shown in FIG. 2 algorithm of the thyristor voltage divider control system.

The proposed voltage divider in comparison with the known frequency converters has the following advantages:
1) in the harmonic composition of the output voltage, the effective value of the main harmonic component of the voltage is not less than 95% of the effective value of the output voltage;
2) increases the reliability of the device by 2 times due to the pause between the intervals of the conducting state of the thyristors, sufficient to turn off the thyristors, and by eliminating short circuits in the circuit;
3) the power factor is increased by a factor of 2 due to the shift in time of the operation of the partitioned loads by half the period of effective use of the voltage at the input of the divider and the reduction of non-linear distortion of the voltage at the input and output of the device.

Claims (1)

 A voltage divider comprising a transformer with a sectioned secondary winding, to the extreme terminals of which two thyristors are connected by an anode and a cathode, and a two-section load is connected by the output of each section to other thyristor electrodes and the sections output is connected to the midpoint of the sectioned secondary winding, characterized in that the output of each two-section load sections are connected to the cathode and anode of two thyristors, the other electrodes of which are connected to different extreme terminals of the sectioned secondary winding informant.

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