SU974523A1 - Frequency converter - Google Patents

Description

FIELD: engineering. technology and can be applied, for example, in electrothermal and other installations.

Known frequency converters with autonomous resonant inverters with inductive-capacitive input, in which the load is included in the circuit of the filter capacitor G13,

The disadvantages of converters with such inverters are low reliability due to the flow of large discharge currents of the filter capacitor through the thyristors when the inversion fails, as well as the complexity due to the need to use devices to limit the emergency current.

Also known frequency converter with a resonant inverter, containing four or more bridges with the inclusion of the load between the vertices of the bridges 12,

The disadvantages of this device are low reliability under emergency conditions due to the discharge currents of the switching capacitors of all bridges of one group located on one side of the load through the thyristors of one of the bridges of the other group when the inversion fails.

These currents flow through the power thyristors, despite the rapid disconnection of the power source.

Closest to the invention is a frequency converter comprising a controlled rectifier, a resonant inverter and a thyristor quenching unit when the inversion fails, the blanking unit is started

10 at the signal of emergency mode sensors 3,

The disadvantages of such converters are the relative complexity and non-reliability during emergency

15 modes due to the flow through the thyristor – inverter of the overcurrent of the protective capacitor, the discharge of the capacitor, the discharge of the comm. tiring capacitors of adjacent bridges (with a multi-joint version),

The aim of the invention is to simplify, increase reliability, speed device shutdown in emergency mode.

25

Claims (3)

The goal is achieved in that a frequency converter containing a controlled rectifier on thyristors, a two-bridge resonant inverter, with an input choke, having two half-windings connected in the DC circuits of the respective bridges, a quenching unit with a damped capacitor, a charging unit Yes, and an extinguishing capacitor, emergency mode sensors, as well as control units of the rectifier and the inverter, two additional diodes are inserted, connected in a counter-series manner and connected in parallel to the winding of the throttle, and Obsed is connected between the total additional diodes and the average output winding of the choke. To increase the switching speed, an additional half-bridge rectifier can be inserted into the converter, connected between the AC terminals of the controlled rectifier and the common point of the additional diodes. Fig, 1 shows a diagram of the frequency converter; in fig. 2 shows an embodiment of the device circuit. The frequency converter contains a resonant autonomous inverter, consisting of two inverter bridges 1, 2, made on thyristors 3-6 and diodes 7-10. The diagonal of each bridge includes switching capacitors 11 and chokes 12. A load 13 is connected between the vertices of the bridges, and the inverter is powered through an input choke 14 from a thyristor rectifier 15. The quench unit consists of a thyristor 16 and a capacitor 17 connected between a common point of additional diodes 18, 19, and the midpoint of the winding, the input of the chokes are 14. The charge of the capacitor 17 is made from the charge block 2 In the bridges 1, 2 there are emergency mode sensors 21, 22 connected to the control unit 23 of the rectifier 15. In the converter e, shown in FIG. 2, a half-rectifier rectifier 24 is additionally introduced. The operation of the frequency converter's quenching unit (FIG. 1) when the output is broken down is carried out in the following way. When the inversion fails, for example, in bridge 1, thyristors 3, 4 are turned on, the sensor simultaneously issues a signal for blocking the control pulses of the rectifier 15, inverter bridges 1, 2 and turning on the thyristor 16 of the quenching unit. As a result, the capacitor 17 begins to discharge towards the emergency current flowing through the thyristors of the rectifier and the thyristors 3, 4 of the inverter bridges 1 and suppresses them, excluding the flow of the emergency current of the discharge of the switching capacitors of the bridge 2 and bridge 1 through the thyristors 3, 4 of bridge 1 Next, the diodes 18, 19 and the energy stored in the input choke 14 and the capacitor 17 are included, is partially dissipated in the active resistances of the two circuits recharging the capacitor 17. These circuits are formed by the thyristor 16, the capacitor 17, the diodes 18, 19 and the corresponding uyuschimi poluobmotkami input choke 14. After recharging the capacitor 17 the thyristor 16 is locked. The converter shown in FIG. 2, works in the same way as described, except that at the initial moment after unlocking the thyristor 16, the thyristors of rectifier 16 instantaneously quench due to the formation of the following quenching circuit: thyristor 16, one of the thyristors of the cathode group of the rectifier 15, OD n from half-bridge diodes 24 and capacitor 17. Thus, the almost instantaneous interruption of the emergency current through the thyristors of the rectifier and the inverter, the complete limitation of the discharge emergency current of the commutative bridge capacitors and the current due to the energy accumulated Noise in the input inductance, as well as a reduction in overvoltages when the thyristors of the inverters are turned off, increase the reliability of the frequency converter. Claim 1. Frequency converter containing a controlled rectifier on thyristors, a two-bridge resonant inverter with an input choke having two half-windings connected to DC circuits of the respective bridges, a quenching unit with a damping capacitor, a block of damping capacitor, sensors emergency mode, as well as control units of the rectifier and the inverter, which is based on the fact that, in order to simplify and increase reliability by reducing current overloads in emergency conditions, two additional itelnyh diode-connected oppositely in series and connected in parallel with the choke coil, wherein the quenching unit is connected between the common point of diodes and additional average output choke winding. 2. The converter according to claim 1, characterized in that, in order to increase shutdown speed, an additional half-bridge rectifier is inserted into it, connected between the AC outputs of the controlled rectifier and the common point of the additional diodes. Sources of information taken into account Examination 1. USSR author's certificate number 318130, cl. H 02 M 7/515, 1971. 2. The author's certificate of the USSR 399038, cl. H 02 M 7/515, 1973. 3. Authors certificate of the USSR 520661, cl. H-02 M 7/10, 1973.