SU1206922A1 - Frequency converter - Google Patents

Description

one

The invention relates to electrical engineering and can be used to convert the frequency of an alternating current.

The aim of the invention is to increase the functional reliability and eliminate losses from the balancing currents by preventing the possibility of the occurrence of short circuits in the windings of the power supply.

FIG. 1 shows a frequency converter; in fig. 2 - time of voltage and current diagram

The frequency converter contains a power source 1, for example a transformer with multiphase secondary windings divided into and phase parts (a, a., A, b, b, b, - i 2 5 - assembled into h potentially separated groups, groups of opposite parallel-connected thyristors 2, control unit 3 and load current sensors 4. The windings of each group of power supply 1 through anti-parallel type: resistors 2 and load current sensors 4 are connected to 11 output pins of converter i (A, B, C), in each of the potentially separated groups are collected about the coils associated with the various output terminals of the converter (for example, the windings,, b, 3 of the power source belonging to different groups of the secondary windings of the power source: a, b, c, and .2, respectively) are connected to the output of phase A. connected to current sensors 4 in load phases and to control transitions of anti-parallel thyristors 2. The control unit may have a synchronization device for communicating the control system with the mains supply a reference signal generator, driving oscillator, comparator for generating mpulsov equality at instants signapa and reference signal from the oscillator, the pulse shaper, logical devices for separately controlling the rectifiers opposite directions of conduction, if the current in the load phase current sensor exceeds the set point and control joint pairs

06922, 2

counter-parallel thyristors of each phase of the load, if the current at the output of the converter is less than the set value of the current sensor of this phase;

5 an output device for generating signals with predetermined parameters and feeding them to control transitions of power thyristors.

FIG. 2 shows temporary

10 diagrams of voltages and currents at the output of the converter (a, b, c) of the thyristor control signals: 5.6- (d), 7.8- (d), 9.10- (e), 11.12- (g ), 13,14- (h), 15,16- (s),

15 17,18- (к), 19,20- (l), 21,22- (m), signals of current sensors to turn on the thyristors in the direct direction of conduction of the phases: A (n), B (p), C (s ) and the reverse direction of the conductance of the phases: A (o), B (p), C (t).

When the frequency converter operates in the secondary windings of the power supply 1, three three-phase EMF systems are induced, of which

25 form a three-phase output voltage with anti-parallel thyristors 2 (Fig. 2a-b). In block 3 of the control, the thyristor control signals are generated.

30 (Fig. 2g-m), which provide cyclic connection of the phase emf systems to the output terminals of the converter (for example, if the emf of phase B of the power supply is used as the reference signal, and the phase emf of the same source is used as the reference signal).

In the zone of small loads, when the current is in phase at the output, the converter does not exceed the sensor setpoint 4 of the current of this phase (Fig. 2 a, b, c). The control signals are simultaneously fed to the counter-parallel thyristors of this phase (shaded

areas in the diagram of FIG. 2, gt). 45,

The absence of the possibility of forming short circuits on the power source is also due to the fact that the zones of simultaneous supply of control signals to pairs of opposite-parallel thyristors belonging to opposite phases at the output of the converter do not intersect.

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Compiled by G. Mycyk Editor N. Pushnenkova Tehred T.Tulik Corrector. Kolb

Order 8731/57

Circulation 632

VNISh State Committee of the USSR

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Branch PPP Patent, Uzhgorod, st. Project, 4

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Claims (1)

A FREQUENCY CONVERTER containing a transformer, the multiphase secondary windings of which are divided into η parts and are assembled in potentially separated groups, as well as a control unit and load current sensors, and the windings of each group are connected via f-parallel thyristors to f | converter output terminals, characterized in that, in order to increase functional reliability and eliminate losses from equalizing currents by preventing the possibility of short-circuit loops on these secondary windings, windings associated with different converter leads are collected in each of the potentially divided groups. Q ... 1206922