SU247392A1 - SINGLE-PHASE STABLE CONVERTER - Google Patents

Description

A known converter of a single-phase current of a stable frequency into a three-phase current of an adjustable low frequency, in which a load phase is connected to one of the terminals of the one-phase current source through symmetrical thyristors.

The purpose of the invention is to increase the range of output frequency control.

A distinctive feature of the proposed converter is that it connects capacitors connected to the load phases to another output of the single-phase current source, and chokes are connected to the power supply circuit of the load phases.

FIG. Figure 1 shows the iincipital diagram of the converter of the phase current and voltage diagram; in fig. 2 - a frequency converter device with a single-phase high-frequency weft link is given; in fig. 3 shows an embodiment of the device.

The frequency converter is made in such a way that the single-phase current output / source through symmetrical thyristors 2, 3 and 4 is connected phases a, b n from load 5 and to terminal 6 - capacitors 7 connected to phases a, b N from load 5 through chokes five.

permissible distortion), i.e. 12.5-15 Hz with

power supply from a single phase network 50 Hz, and the lower

limit - 2.2 Hz. To improve the shape of the output voltage can be applied

smoothing, non reactors.

FIG. 2 shows a circuit diagram of a converter with an intermediate circuit of increased frequency, represented by a link, and a combination of a single-ended parallel inverter 9 with an implicitly expressed DC link (source of higher frequency), operating with self-excitation, and a single-phase converter W of the intermediate circuit of high frequency in three phase current

widely adjustable or stable lower frequency with a reduced number of power controlled gates.

In this converter, the three-phase voltage of the industrial frequency of 50 Hz is first converted into a single-phase voltage of increased frequency / pr by using a single-cycle parallel inverter 9 with an implicit DC link operating with self-excitation in the mode of iodiodic reloading of the switching capacitor 11. Then the resulting single-phase overvoltage / dp voltage (which can vary within known limits) is converted to a three-phase

lower frequency / 2 with another converter 10. The latter is made according to the scheme, consisting of three symmetric thyristors 12, 13 and 14, connected in a star, and capacitor stars 15, to the zero points of which the resulting single-phase intermediate circuit voltage is increased frequencies, and a three-phase load 19 (in our case, an asynchronous motor) is connected to the three output ends of the said stars connected in phase to the smoothing reactors 16, 17, 18.

This converter does not impose stringent requirements on the shape of the intermediate circuit voltage of increased (carrier) frequency, and also allows the intermediate circuit voltage frequency to vary within fairly wide limits, and therefore no special devices are required to stabilize the carrier frequency.

FIG. 3 shows a converter circuit with a higher frequency intermediate circuit, which is a combination of a multiplier (triple) frequency 20 of the Spinelli system (high frequency source) and a single-phase intermediate frequency converter 21 of the higher frequency intermediate circuit into a regulated three-phase current over a wide range or a stable lower frequency with a reduced the number of power controlled valves. The diagram shows cosine capacitors 22, capacitors for lateral compensation 23.

This converter also first converts the three-phase voltage of industrial frequency 50 Hz to single-phase voltage of high frequency using a static electromagnetic frequency multiplier of 20, 2, 3, 4, 6 and 8 or 9 times of any known system. Then, the resulting single-phase voltage of the increased frequency is converted to a three-phase voltage regulated over a wide range over a wide range.

low frequency using another converter 21, made according to a circuit consisting of three symmetrical thyristors 24 connected to a star, and stars of capacitors 25, to the zero points of which the resulting single-phase intermediate-circuit voltage of the increased frequency is supplied, and to the three phase ends combined These stars connect three-phase load 27 via smoothing reactors 26 (in this case, an induction motor).

Regulation of the output voltage is made regardless of the frequency, which allows you to get any law of frequency

management

These converters with an intermediate circuit of increased frequency when powered from a 50 Hz network and using the properties of natural switching provide frequency

speed control of asynchronous motors in the frequency range from 2 to 0.20-0.25 fnp Hz (where fnp is the intermediate circuit frequency) depending on the permissible output voltage distortion

with a slight deterioration in performance compared to the power supply of motors from a source with sinusoidal voltage of the corresponding frequency.

Subject invention

The converter of single-phase current of stable frequency into three-phase current of adjustable low frequency, in which to one of

the single-phase current source terminals through the symmetrical thyristors are connected to the load phase, characterized in that, in order to increase the output frequency control range, to another of the source terminals

single-phase current capacitors connected to the load phases are connected, and torssels are included in the power supply circuit of the load phases.

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