Start of section
Production, amateur
Radio amateurs
Aircraft model, rocket-model
Useful, entertaining 		Stealth Master
Electronics
Physics
Technologies
Inventions 		Secrets of the cosmos
Secrets of the Earth
Secrets of the Ocean
Tricks
Map of section
Start
Forum
Use of the site materials is allowed subject to the link (for websites - hyperlinks)

Navigation: =>

Home / Patent catalog / Catalog section / Back /

DEVICES AND METHODS OF ECONOMY AND PRESERVATION OF ELECTRICITY
INVENTION
Patent of the Russian Federation RU2279179

INVERTER CURRENT

INVERTER CURRENT

The name of the inventor: Silkin Evgeniy Mikhailovich (RU); Kuzmin Alexander Fedorovich
The name of the patent holder: Closed Joint-Stock Company "Kontaktor"
Address for correspondence: 432001, Ulyanovsk, ul. K. Marx, 12, ZAO Kontaktor, A.F. Kuzmin
Date of commencement of the patent: 2005.01.24

The invention relates to a converter technique and can be used as a power source for an induction heater. The technical result is provided - increasing the reliability of the current inverter (IT). IT contains the IT connected to the input terminals (TH) of IT through the first and second chokes (DR) of the filter (1), (2) the single-phase bridge (OM) on four thyristors (TI) (3-6), four series circuits The capacitor (KE) (7-10) and the resistor (PE) (11-14), the PC from the first switching DC (15), the first switching KN (16), the shunt output of the ITU, and the second switching DC (18) In the diagonal of alternating current OM, shunted by the second commutating SC (19), a silicon symmetric voltage limiter (OH) (20), shunting the direct current OM of the OM. Consecutively with TI (3-6) are shunted by counter CIs (25-28). CIs (21-24) are shunted by OH (29-32). PC from KH (7-10) PE (11-14) shunt the PC of the TI connection (3-6) and DI (21-24).

DESCRIPTION OF THE INVENTION

The invention relates to a converter technique and can be used as a power source for an induction heater.

A current inverter is known comprising a single-phase thyristor bridge connected to the input terminals of the current inverter, four serial circuits of a capacitor and a resistor, a serial circuit from the first commutating reactor, a commutating capacitor shunting the output terminals of the current inverter, and a second commutating throttle included in Diagonal of alternating current of a single-phase bridge, series circuits from a capacitor and a resistor shunt thyristors (Thyristor-capacitor power supplies for electrotechnology / OGBulatov, AI Tsarenko, VD Polyakov, etc. - M .: Energoatomizdat, 1989 180 C.).

The disadvantage of the current inverter is low reliability of operation due to high values ​​of switching losses in thyristors, low overload capacity, high overvoltages on the elements of the current inverter circuit when thyristors are switched off.

A current inverter is known which contains a single-phase thyristor bridge connected to the input terminals of the inverter through the first and second filter chokes, a commuting capacitor that shunts the output terminals of the current inverter (P. 4589059 USA, IC No. 02 M 5/458, Method of starting a current- Fed inverter with self-excitation / M.Tanino // OB-1986.-N5).

The disadvantage of the current inverter is low reliability of operation due to high values ​​of switching losses in thyristors, low overload capacity, high overvoltages on the elements of the current inverter circuit when thyristors are switched off.

The closest in technical essence to the invention is a current inverter (P. 2155433 RF, MKI H 02 M 7/521., Current Inverter / Silkin EM, etc. - Proclaimed 01.03.94, Published on 10.06.96 .-- Bul N 16), which is considered as a prototype.

The prototype contains a current connected to the input terminals of the inverter through the first and second filter chokes, a single-phase thyristor bridge, four series circuits of a capacitor and a resistor, a serial circuit from the first commutating choke, a first commutating capacitor shunting the output terminals of the current inverter, and a second commutating throttle, In a single-phase AC diagonal, shunted by a second commutating capacitor, a silicon symmetrical voltage limiter, shunting the DC terminals of a single-phase bridge, successive circuits from the capacitor and a resistor shunt the thyristors.

The disadvantage of the prototype is low reliability of operation due to high values ​​of switching losses in thyristors, low overload capacity of thyristors in conditions of hard switching, high overvoltages on the elements of the inverter circuit when thyristors are switched off.

The invention is directed to solving the problem of increasing the reliability of the current inverter, which is the purpose of the invention.

This goal is achieved by the fact that in a current inverter, which contains a single-phase thyristor bridge connected to the input terminals of the current inverter through the first and second filter chokes, four successive circuits of the capacitor and the resistor, a serial circuit from the first commutating reactor, the first switching capacitor shunting the output pins Current inverter and a second commutating choke connected to the diagonal of alternating current of a single-phase bridge, shunted by a second switching capacitor, a silicon symmetrical voltage limiter, shunting the DC terminals of a single-phase bridge, sequential diodes are connected in series with thyristors, thyristors are shunted by counter diodes, successive diodes are shunted by silicon symmetric Voltage limiters, series circuits from the capacitor and the resistor shunt the series circuits of the connection of the thyristor and the series diode.

A significant difference characterizing the invention is an increase in the reliability of the operation of the current inverter by an induction heater due to a reduction in switching losses in thyristors, switching overvoltages on the elements when thyristors are switched off.

Increasing the reliability of the current inverter operation on the induction heater is the result obtained by the introduction of new elements and connections, i. E. Distinctive features. Thus, the distinguishing features of the claimed current inverter are significant.

The figure shows the current inverter circuit.

Current inverter circuit

The current inverter contains the current inverter connected to the input terminals of the current inverter through the first and second filter throttles 1, 2 a single-phase bridge on four thyristors 3-6, four series circuits from the capacitor 7-10 and a resistor 11-14, a serial circuit from the first commutating reactor 15, A switching capacitor 16 shunting the output terminals 17 of the current inverter and a second commutating choke 18 included in the diagonal of the alternating current of the single-phase bridge shunted by the second switching capacitor 19, a silicon symmetrical voltage limiter 20 shunting the DC terminals of the single-phase bridge.

Sequential diodes 21-24 are successively connected with thyristors. Thyristors are shunted by counter diodes 25-28. The series diodes are shunted by silicon symmetrical voltage limiters 29-32. Serial circuits from the capacitor and the resistor shunt the series circuits of the connection of the thyristor and the series diode.

INVERTER CURRENT WORKS AS FOLLOWS:

The thyristors of the diagonals of the bridge of the inverter 3, 6 and 4, 5 are turned on alternately at a frequency equal to the frequency of the output voltage of the current inverter determined by the natural frequency of the parallel oscillatory circuit formed by the induction heater 17 and the first switching capacitor 16. Moreover, the inclusion of a further pair of thyristors 3, 6 or 4 , 5 occurs ahead of the moment when the instantaneous value of the voltage across the capacitor 16 of the parallel oscillatory circuit passes through the zero value. This circuit has a high quality factor (10-40), as a result of which the voltage on the induction heater 17 and the capacitor 16 has a shape close to a sinusoidal one. The inductance of the filter chokes 1, 2 has a large value and is selected from the condition of smoothing the ripple of the input current. Therefore, the input current of the current inverter is smoothed, and the current flowing through thyristors 3-6 and successive diodes 21-24 has a shape close to rectangular. The total period of the output voltage consists of two intervals (half-periods) corresponding to different combinations of the switched on and off states of the thyristors of the single-phase bridge 3-6. Electromagnetic processes in each of the half-cycles proceed similarly. When unlocking thyristors 3-6, the first and second switching capacitors 16, 19 are recharged along the circuits 16-18-24-6-2 - "-" - "+" - 1-3-21-15-16 and 19-24- 6-2 - "-" - "+" - 1-3-21-19. Simultaneously with the recharging of the first and second commutating capacitors 16, 19, the continuous discharge of these capacitors through the induction heater (load circuit) 17 takes place via circuits 16-17-16 and 19-15-17-18-19. A voltage of conditionally positive polarity is applied to the induction heater 17. At the moment of switching on thyristors 3, 6, the voltage on the first and second switching capacitors 16,19 is conditionally negative ("+" on the lower plates in the drawing). The level of this voltage is

U = ((v E) / cosb) sinb,

Where v is a constant circuit factor, E is a constant voltage at the input of the current inverter, b is the advance angle (the angle between the instant of switching on of the next thyristor pair and the moment of voltage transition on the capacitors 16, 19 through zero value). Therefore, at the moment of switching on the transistors 3, 6 the capacitors 16, 19 and start discharging along the circuits 16-18-24-6-4-22-15-16, 16-18-23-5-3-21-3-15-16 And 19-24-6-4-22-19, 19-23-5-3-21-19. The chokes 15, 18 limit the discharge rate of the first switching capacitor 16 having a larger capacitance than the second switching capacitor 19 and the rate of current decay (rise) through the thyristors 3-6 and the successive diodes 21-24. The current of thyristors 4, 5 and successive diodes 22, 23 falls from the maximum value to zero, and the current of thyristors 3, 6 and successive diodes 21, 24 increases from zero to maximum. Thus, switching of thyristors 3-6 and successive diodes 21-24 is carried out. When the reverse current of the successive diodes 22, 23 (recovery) is broken, the discharge current of the capacitors 16, 19 is closed through the capacitors 8, 9 and the resistors 12, 13 of the RC circuits along the circuits 16-18-24-6-8-12-15-16, 16-18-13-9-3-21-15-16 and 19-24-6-8-12-19, 19-13-9-3-21-19. The energy accumulated in the electromagnetic field of the first and second commutating chokes 15, 18 (a and of the connecting busbars) is partially transferred to the capacitors 8, 9 and partially dissipated in the resistors 12, 13 and the induction heater 17. When the voltage across the capacitors 8, 9 is exceeded The voltage of the silicon symmetrical voltage limiters 30, 31 includes the counter diodes 26, 27 and the energy of the capacitors 8, 9 is further dissipated on said silicon symmetrical voltage limiters 30, 31 in the circuits 8-26-30-12-8 and 9-13-31-27 -9.

Switching losses in thyristors 4, 5 and successive diodes 22, 23, and the levels of commutation overvoltages on the elements of the current inverter circuit are limited. Voltages on switching capacitors 16, 19 do not have time to change the sign in the commutation interval, and a reverse (negative) voltage is applied to successive circuits of the thyristor-series diode 4, 22 and 5, 23. Further, upon operation of the thyristors 3, 6 after the termination of the switching interval in the time interval when the voltage on the capacitors 16, 19 remains conditionally negative, the capacitors 8, 9 are discharged to the induction heater 17, the energy stored in the capacitors 8, 9 being returned (recovered) Into the induction heater 17 until they are completely discharged. Silicon symmetrical voltage limiters 30, 31 provide additional protection of thyristors 4, 5 and successive diodes 22, 23 from negative voltage overvoltages at shutdown. The silicon symmetrical voltage limiter 20 reduces the magnitude of the negative polarity overvoltage pulse when the serial diodes 22, 23 are turned off at the DC terminals of the bridge and protects the current inverter circuit components from positive positive polarity surges when the induction heater circuit breaks 17. In the application interval of the negative voltage to the series of circuits, the thyristor - a sequential diode 4, 22 and 5, 23 thyristors 4, 5 restore their control properties. The lead interval is selected from the condition of providing sufficient time for the thyristors to restore 4, 5 their control properties.

With the further operation of the current inverter, the voltage across the switching capacitors 16, 19 changes sign and becomes conditionally positive. After the first interval equal to half the period of the AC output voltage, the thyristors 4, 5 are switched on. Electromagnetic processes in the current inverter after switching on the transistors 4, 5 proceed similarly described. The next inclusion of transistors 3, 6 ends the period. In the induction heater 17, a total output AC voltage wave is generated. Part of the overvoltage energy accumulated in the electric field of the second switching capacitor 19 at the switching intervals is used directly in the load circuit 17. As a result, with the same efficiency of reducing the overvoltage, it is possible to perform RC circuits 7, 11-10, 14 for a smaller installed power and reduce losses In thyristors 3-6 and successive diodes 21-24.

Compared with the prototype, the reliability of the current inverter is greatly improved by reducing switching losses and overvoltages. This is ensured by a rational set and mutual reservation of the protective circuits. Inadmissible impulse overvoltages on thyristors and diodes are absent. Moreover, direct (emergency) and reverse polarity overvoltages are limited. In particular, when the load circuit breaks 17, the overvoltage levels on the current inverter elements are limited at the level of the nominal voltage of the silicon symmetric voltage limiter 20. The commutating reactors 15, 18 limit the rates of rise and fall of the current of thyristors 3-6 and successive diodes 21-24 for commutations, Which reduces the levels of switching overvoltage when working on an induction heater. The reverse voltage on thyristors 3-6 is absent, which is ensured by the inclusion of counter-diodes 25-28 into the circuit. As a result, switching losses in thyristors 3-6, which have a lower overload capacity than diodes 21-24, are significantly reduced when switched off. Switching losses and overvoltages in the recovery of successive diodes 21-24 and are reduced due to the limitation of overvoltage levels by silicon symmetric voltage limiters 29-32, installed in the immediate vicinity of the protected circuits of the thyristor diode 3, 21-6, 24. All this increases the reliability of the inverter Current. Thyristors 3-6 in the claimed current inverter may have a lower voltage class, which allows them to be performed with shorter turn-off times. As a result, the stability of the current inverter is increased to disrupt the inverting. The series diodes 21-24 can have a higher voltage class with the same dynamic characteristics compared to thyristors 3-6. Overvoltages that lead to the failure of semiconductor devices in current inverters working in advance are known to take place when the devices are turned off. The possibility of using serial diodes 21-24 to higher voltage classes allows to provide higher reliability of inverter operation. Increasing the reliability of the inverter current is estimated by the time between failures. The claimed inverter current compared with the prototype when performed on the same output power has a time-to-failure time of a higher 1.3-1.4 times.

In comparison with the prototype, the efficiency of the current inverter increases due to the reduction of losses in circuit elements, including damping RC-circuits.

Compared with the prototype, the cost of the current inverter elements is reduced due to the possibility of using elements (thyristors, diodes, capacitors, etc.) at lower permissible voltages.

CLAIM

A current inverter comprising a single-phase thyristor bridge connected to the input terminals of the inverter through the first and second filter chokes, four serial circuits of the capacitor and a resistor, a serial circuit from the first commutating reactor, a first commutating capacitor shunting the output terminals of the current inverter, and a second commuting choke Connected to the diagonal of alternating current of a single-phase bridge, shunted by a second switching capacitor, a silicon symmetrical voltage limiter, shunting the DC terminals of a single-phase bridge, characterized in that successive diodes are connected in series with thyristors, thyristors are shunted by counter diodes, successive diodes are shunted by silicon symmetrical voltage limiters, The series circuits from the capacitor and the resistor shunt the successive circuits of the connection of the thyristor and the series diode.

print version
Publication date 17.02.2007gg