SU1501235A1 - Variable self-excited inverter - Google Patents

Abstract

The invention relates to a converter technique and can be used in installations for induction heating. The goal is to increase the work stability. The inverter contains a bridge on four thyristors 2-5. The bridge diagonal includes a switching choke 6 with a secondary winding 7 and a switching capacitor 8. The cathodes of the return diodes 12, 13 are connected to the ends of the windings of the autotransformer 14, the middle output of which is connected to the anode group of the bridge, the midpoint of the circuit of two capacitors 15, 16 through a resistor 17 During the moments of pause, capacitor 9 is charged by the power source and the voltage difference across the capacitors 8, 9 (reverse voltage across the thyristors) is reduced. 2 hp ff, 1 ill.

Description

7i

.x

r rXl9i

W

57

tu "

52S

7

T1

o2

hk

five

 II

3150

The invention relates to converter technology and can be used in the development of adjustable power supplies for induction heating systems.

The purpose of the invention is higher operational stability, increased reliability and efficiency.

The drawing shows a schematic diagram of the inverter.

The inverter contains a thyristor bridge connected to four thyristors 2-5 with a commutating 11r1m choke 6 connected via a choke filter, having a secondary winding 7, and a switching capacitor 8 in the AC diagonal. Parallel to the bridge, there is a circuit of a series-connected filter capacitor 9, a load 10, and additional droplets 11. The opposite terminals of the alternating current diagonal of the thyristor bridge are connected to the anodes of the return diodes 12 and 13, the cathodes of which are connected to the ends of the windings of the autotransformer 14 whose average output is connected to the thyristor anode group bridge and the midpoint of the serial circuit of the capacitors 15, 16 through a resistor 17. The secondary winding of the switching throttle is connected to the AC terminals one aznogo diode bridge 18, the negative and positive DC terminals TO- ka are connected to respective poles of the filter capacitor. Inverter in the steady mode works as follows.

At simultaneous unlocking of the thyristors of the diagonals 2, 5 (or 3, 4), the oscillating recharge of the switching capacitor 8 in the chain 8-5-11-10-9-2-6-8 begins. The current through the load 10 changes its direction and begins to flow in the direction conventionally taken as positive (indicated by the arrow in the drawing). After recharging capacitor 8 and decreasing the oscillating current of the circuit

to zero, the thyristors 2, 5 are turned off. There is a pause in the operation of the inverter, during which the current through the load 10 flows from top to bottom and the capacitor of the filter 9 of the capacitor 9 is charged through the choke of filter 1 from the power source. After the pause, the thyristors of the opposite diagonal (3, 4) and the processes in

0 5 0 5

0 5

0

e

The vertor repeats. During one cycle of operation of all thyristors of the bridge, 2–5 n load, two complete periods of output AC voltage are obtained.

When adjusting the output power (the power released in the load), the delay angle is entered between; the first unlocking moment of the thyristors of the cathode group of the bridge (2 and 5) relative to the moments unlocking the thyristors of the anodic group (2 and 4). In this case, in the delay interval, a partial control discharge of the switching capacitor 8 along the circuit occurs, without a load. In this case, the power in the load is dependent on the delay angle and decreases as it increases.

For example, thyristor 2 is unlocked. An oscillatory recharge of capacitor 8 starts along circuit 8-13-14-2-6-8 (capacitor 8 when unlocking thyristor 2 is charged as shown in the drawing). The discharge circuit does not include the load 10. After the delay interval, the thyristor 5 turns on. Diode 13 turns off, because when the thyristor 5 is turned on, the discharge circuit of the capacitor fi-ptr 9 is formed along the circuit 9-14-13-5-11-10-9 . The loop current is directed oppositely to the diode 13 current. After the diode 13 is locked, further recharging of the capacitor 8 continues along the circuit 8-5-11-10-9-2-6-8, including the load. After the current drop in the circuit 8-5- -11-10-9-2-6-8 to zero, the thyristors 2, 5 are turned off, and there is a pause in the operation of the inverter. After a pause, the thyristor 4 is turned on and then the processes are repeated (diode 12 is working). Adjusting the angle of delay, regulate the level of energy supplied to the load 10 when recharging capacitor 8.

When regulating at the time of switching on the thyristors of the cathode group (3, 5), the current of the return diodes 12 and 13 drops to zero and further, due to the presence of charge in the structure of the cell, some time flows in the negative direction. After recombination of charge carriers in the structure of the diodes, they abruptly interrupt the current. In this case, a path is formed for the current of the parts of the autotransformer, caused by the energy stored in the electric () magnet11 (1M field of the parts of the autotransformer, rui chains 14-16-17 or 14-15-17.

i50i;

When the voltage on the secondary winding exceeds 7 com- | the voltage that is generated by the dropping voltage 6 (and to the on-capacitor of the filter 9, the single-diode diode is unlocked; opt 18 and the voltage is limited) The voltage at the voltage level on the filter capacitor. This allows the appropriate selection of the number of windings 7 to remove 10 switching overvoltages occurring when the current of the commutating throttle 6 is interrupted, the overvoltage is caused by the traction in the electromagnetic field of the throttle 6 at the special voltage on the thyristors).

Thyristor mutations and current flow of capacitances of pn junctions of thyristors during their shutdown and reverse currents of thyristors associated with the accumulation of carriers in the structure. The computational overvoltage energies are high (especially at high frequencies) and dissipated on the inverter elements, worsening the conditions of their operation. The secondary winding 7 of the commutating throttle 6 and the single-phase diode bridge 18 represent a regenerative circuit that operates to remove switching overvoltages. When the bridge 18 is operating, the switchboard power surplus is returned (recovered) to the inverter’s power source to a sufficiently full extent.

Claims (3)

I Changes in the load resistance from the nominal value in the direction of a short circuit or XX leads to the appearance of closed circuits including reactive elements, anode group thyristors and return diodes separated from the power source, which causes the external characteristic rigidity. In mode XX (open circuit of load 10) oscillations are excited inside the inverter bridge. In this case, the thyristors of the cathode group (3, 5) are not switched on, and the switching capacitor is recharged along the chains 8-13 (12) -14-2 () - 6-8. The secondary winding 7 of the switching droplets 6 and the diode bridge 18 are low-power elements that work only at the moments of the occurrence of switching overvoltages, they do not complicate the inertors and their use does not lead to an increase in weight and weight indicators and a noticeable additional consumption of materials. Performing an RC circuit from an elementary 15-17 g single resistor 1336 simplifies its design and cooling. The use of these elements will significantly try stability, efficiency and reliability of the inverter. Compared to the prototype, the Mbtft inverter has a higher availability of operation. During the moments of pause, the capacitor of the filter 9 is recharged from the power source of the inverter and the voltage difference across the switching capacitor 8 and the filter capacitor 9 decreases (about 0 five An additional bit of commuting | (its capacitor through the windings of the autotransformer in the prototype is an additional factor that reduces the voltage difference, which leads to the transition of the reverse voltage on the thyristor when it restores the control properties to a positive one in the pause interval and sharply reduces the time provided for restoring control Capacity and Inversion Disruption. In the claimed inverter, due to the inclusion of an additional return diode, there is no switching circuit of the switching capacitor in the interval The voltage and the voltage on it are kept constant. There are no conditions to enable. from the return diodes in the decay intervals of the current of the switching circuit, which caused the current to be drawn in through the forward thyristors (in this case anodic group of thyristor bridge. Q time reduction provided them to restore the control properties, violation of the switching conditions and led to a breakdown of the inversion. To ensure these f. conditions, the switching choke is made, included in the diagonal of the alternating current of the thyristor bridge, and inductive elements are not included in series with the thyristors. Q The inclusion of the chokesel 11 in the filter capacitor circuit 9 and the load U provides a low level of direct voltage on the anode group thyristors when the thyristors of the anode group are unlocked and controlled by dividing the sum of the voltages on the filter capacitor 9 and the load 10 between the choke 11 and the working part autotransformer 14. It is voltage it can be applied abruptly and lead to the spontaneous switching on of the anode group thyristors due to dj d. high (inclusion due to the currents of the power supply and capacitances of pn junctions). At the same time, the choke 11 performs protective functions to ensure a low rate of increase of the current of the thyristors of the cathode group during regulation and breakdown of the inversion, In comparison with the prototype, the efficiency of the inverter in The maximum load mode that is delivered to the ends of the windings is connected to the power load, since there is no circulation current of the switching capacitor through the windings of the autotransformer, the reliability of the inverter operation increases, because the switching overvoltage of the return diodes is limited by switching on the RC - chains of elements 15,16,17. Compared to the prototype, the inverter CGTL is increased due to the energy recovery of a commutational overvoltage, which occurs when the current of the commutating throttle 6 is interrupted by the secondary current 7 and single phase 30 my diode Til 1B. an autotransformer, anodes - with various names of the alternating current diagonal of the thyristor bridge, the average output of the autotransformer windings is dinine with the anode group of the thyristor bridge, the alternating current diagonal of which is connected to the switching capacitor 1 st of the throttle in the diagonal of the alternating current and an additional throttle. 2. Inverter pop, 1, otlncha yu and so that, in order to improve reliability, it is equipped with a resistor and a series circuit of two capacitors connected between the cathodes of the return diodes, and the middle point of the capacitors connected to the average output windings of the car - tra} 1sformator through the specified resistor. The stability and reliability of the inverter operation is reduced in the number of inversion failures when operating on a load with varying parameters over a wide range (installation for induction heating) and the output of thyristors and diodes failing due to switching overvoltages; current return diodes. Formula gaining one . Adjustable autonomous inverter containing connected to the input Editor M.Tovtin Compiled by I. Zherebina Tehred M. Khodanych Order 4887/54 Circulation 6A6 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 through a filter choke, we output a thyristor bridge with a switching capacitor in the diagonal of alternating current and serial from the capacitor f1c: τra and output pins, with the filter capacitor connected to the anode group of the bridge, autotransformer, first return diode, switching louder and y and u with that. That, in order to improve operation stability, a second return diode is introduced, with return cathodes  connected to the ends of the windings autotransformer, anodes - with opposite terminals of the alternating current diagonal of the thyristor bridge, the average output winding of the autotransformer is connected to the anode group of the thyristor bridge, the alternating current diagonal of which is connected to the 1st choke in series with the switching capacitor, and an additional choke is included in the above-mentioned serial circuit. 2. Inverter pop, 1, otlnchu yu and so that, in order to increase reliability, it is equipped with a resistor and a series circuit of two capacitors connected between the cathodes of the return diodes, and the middle point of the capacitors is connected to the average output windings of the auto- tra} 1sformator through the specified resistor. 3. The inverter is according to claims 1 and 2, which also means that, in order to increase efficiency, it is equipped with a single-phase diode bridge, and the switching choke is made with a secondary winding, the terminals of which are connected to the single-phase AC terminals a diode bridge connected by a direct current terminal to the filter capacitor, with a positive terminal to the thyristor anode group. Proofreader T.Paly Subscription