RU2249906C1 - Three-phase voltage converter - Google Patents

Abstract

FIELD: feeding high-frequency ac voltage loads.

SUBSTANCE: proposed three-phase converter has diode switching unit incorporating uncontrolled diode bridge built around six diodes with three-phase three-wire mains connected to its input. Connected to bridge output are two series-connected capacitors and also two power transistors, emitter of one power transistor being connected to cathode group of diodes and emitter of other power transistor, to anode group; collectors of power transistors are interconnected at common point and connected to one of terminals of transformer primary winding. Other terminal of the latter is connected to neutral wire and to emitters of two controlled transistors whose collectors are connected through resistors to bases of power transistors. Bases of control transistors are connected through other resistors to common connection point of capacitors. Load is connected to transformer secondary winding.

EFFECT: simplified design and reduced mass and size of device.

1 cl, 2 dwg

Description

The invention relates to the field of converting technology and can find application for powering consumers of alternating current voltage of high frequency.

A known three-phase voltage converter of high frequency with a single-phase output, containing in the power part a multiphase controlled valve bridge, control unit and load (SU No. 819908, N 02 M 5/27, publ. 07.04.81).

A disadvantage of the known Converter is the incomplete symmetry of the output voltage, low input power factor and increased installed power of the valve block.

A device for converting a three-phase alternating voltage into a single-phase, containing a single-phase transformer, three pairs of on-parallel connected thyristors connected to one end of the primary winding of the output transformer, the other end of which is connected to the zero input terminal, and a control system (SU No. 1815766, IPC 5, H 02 M 5/27, publ. 05.15.93).

A disadvantage of the known device is the presence of six controlled power switches and the complexity of the control system, including, in particular, three synchronization transformers.

The technical result consists in simplifying the device and reducing its overall dimensions.

The essence of the invention lies in the fact that in a three-phase AC voltage converter containing a valve switch and a single-phase transformer, the valve switch includes a six-armed uncontrolled bridge, to the input of which a three-phase three-wire network is connected, and the bridge output is connected to two capacitors connected in series. The anode and cathode groups of the bridge are connected to emitters of power transistors, the collectors of which are combined into a common point and connected to one of the terminals of the primary winding of a single-phase transformer, and the other terminal of the primary winding of a single-phase transformer is connected to the neutral wire and emitters of the control transistors, whose collectors are connected through resistors to bases of power transistors, and bases of control transistors through other resistors - to a common point of connection of capacitors.

In Fig.1 shows a diagram of the Converter, Fig.2 is a diagram of the phase voltages of the supply network.

The converter consists (Fig. 1) of a gate switch, including an uncontrolled gate bridge, made on diodes 1-6, to the input of which a three-phase three-wire network A, B, C is connected. To the bridge output are connected in series capacitors 7 and 8, as well as power transistors 9 and 10. The emitter of the power transformer 9 is connected to the cathodic group of valves, and the emitter of the power transformer 10 is connected to the anode group, the collectors of which are connected to a common point and connected to the terminal M of the primary winding of the single-phase transformer 17. Terminal N is primary ohm winding of a single-phase transformer 17 is connected to the neutral wire and emitters of the control transistors 11 and 12, the collectors of which through resistors 13 and 14 are connected to the bases of power transistors 9 and 10. The bases of the control transistors 11 and 12 are connected through common resistors 15 and 16 to the common point of the capacitors 7 and 8. A secondary load 18 is connected to the secondary winding of the single-phase transformer 17.

The operation of the circuit occurs in accordance with the vector diagram (figure 2), which shows the phase voltage vectors U _A , U _Z , U _b , U _X , U _C , U _Y , following each other through 60 el. hail.

The formation of an alternating voltage occurs as follows: under the action of a phase voltage U _A at the cathodes of the diodes 1, 3, 5 with respect to the zero wire, a positive half-wave of voltage is formed with a frequency equal to three times the frequency of the network. The ripple voltage through the capacitor 7 is supplied to the base of the control transistor 11 relative to the average level. When the amplitude of the pulsations reaches the unlock threshold of the transistor switch, the control transistor 11 and the power transistor 9 go into the open state. The current will flow from phase A through the diode 1, power transistor 9, the primary winding of the transformer 17 to the neutral wire and magnetizes the core of the magnetic circuit in the opposite direction to the previous state. When the amplitude of the ripple decreases below the unlock threshold of the transistor switch, the control transistor 11 and the power transistor 9 are locked.

Under the action of the phase voltage U _Z at the anodes of the diodes 4, 6, 2 with respect to the neutral wire, a negative voltage half-wave is also formed with a frequency equal to the triple network frequency. The ripple voltage through the capacitor 8 is supplied to the base of the control transistor 12 relative to the average level. When the amplitude of the pulsations reaches the unlock threshold of the transistor switch, the control transistor 12 and the power transformer 10 go into the open state. Current flows from the neutral wire through the primary winding of transformer 17, power transistor 10, diode 2 to phase C of the supply network. In this case, the magnetic core is magnetized in the opposite direction to the maximum value of magnetic induction.

Further work of the circuit elements is carried out in accordance with figure 2 from the action of the corresponding phase voltage in the following order:

U _B : 3-9-17-N;

U _X : N-17-10-4;

U _C : 5-9-17-N;

U _Y : N-17-10-6.

Thus, over the period of the supply network, the magnetization reversal of the core of the magnetic circuit occurs through 60 el. hail, which allows to obtain a voltage of triple frequency on the secondary winding of the transformer.

Since the proposed device contains a smaller number of elements both in the power unit and in the control system, therefore, it is simpler and allows to reduce the overall dimensions of the converter as a whole.

Claims (1)

A three-phase AC voltage converter comprising a gate switch and a single-phase transformer, characterized in that the gate switch includes a six-armed uncontrolled bridge, to the input of which a three-phase three-wire network is connected, and the bridge output is connected to two capacitors connected in series, the anode and cathode groups of the bridge are connected to emitters of power transistors, the collectors of which are combined into a common point and connected to one of the terminals of the primary winding of a single-phase transformer pa, and the other clamp of the primary winding of a single-phase transformer is connected to the neutral wire and emitters of the control transistors, the collectors of which are connected through the resistors to the bases of the power transistors, and the bases of the control transistors through other resistors to the common point of the capacitors.

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