JPS5911267B2 - thyristor inverter - Google Patents

Description

[Detailed Description of the Invention] The present invention uses a thyristor as a switching element.
This invention relates to the circuit configuration of an inverter that converts DC power to AC power.

10. Recently, as thyristors have been made to have higher withstand voltages and larger currents, efforts have been made to increase the capacity of thyristor inverters that use them as switching elements.

Recently, this inverter has come to be used as a power source for electronic computers instead of a rotary power source15. Additionally, along with this, there is an increasing need to make devices smaller, lighter, and more efficient. For example, a conventional inverter is shown in Fig. 1 (Japanese Patent Publication No. 39-29909).
When the thyristor 20Th_1 is energized, a current 12 flows from the DC power supply E1 to the load Z. Next, when the thyristor Th_2 is ignited, a current of 12 flows from the DC power supply E2 to the load Z.
A current with the opposite polarity to the current i2 flows.

The thyristors Th_1 and Th_2 are fired alternately to supply 25 AC power to the load Z. Transformer T) Reactor 1
) Capacitors C, C' and diodes D_, D_2 constitute a commutation circuit, and when one of the thyristors Th_1 and Th_2 is turned on, the other one is forcibly turned off. To explain the commutation operation of this circuit, the thyristor current T
Assume that h_1 is energized and load current i2 is flowing. At this time, the voltage of capacitor C is zero, and the voltage of capacitor c' is at the same level as the sum of DC power supplies E1 and E2 with the polarity shown in the figure. Next, when the thyristor Th_2 is ignited, the voltage of the capacitor σ causes a current i1 to flow through the lower half winding of the reactor 1 and the 35 transformer T, and at the same time, the voltage developed in the upper half winding of the transformer T causes the diode Charging current 12 of capacitor C flows through D_1. These currents 11 and i2 are the resonance currents of the reactor l and capacitors C and C', and the voltage of the capacitor C' becomes zero, and when the capacitor C is charged to the sum of the levels of the torrent power sources E and E2, the current disappears. . While current is flowing through the diode D, the forward voltage drop (approximately 1 volt in the case of a silicon diode) causes the thyristor Thl to be reverse biased and extinguished. A current having the opposite polarity to Iz flows from the DC power supply E2 to the load Z through the thyristor Th2. When the thyristor Th is turned on after a certain period of time, a discharge current of the capacitor C is generated and at the same time a charging current of the capacitor C' flows through the diode D2, and the forward voltage drop of the diode D2 causes the thyristor Th2 to be turned off. This will return you to the initial state. One of the drawbacks of this conventional example is that the thyristor Th
Thyristors Thl and Th2 must be in the non-conducting state to control the voltage applied to the load. period). The second drawback is that when the load Z suddenly becomes heavy, that is, when the current 1z suddenly increases, a voltage with the polarity shown in the figure is induced in the winding of the transformer T.

This means that capacitor C', which is charged to the sum of the voltage of DC power sources E1 and E2, is discharged, and capacitor C, whose voltage was zero, is charged, and at this time, commutation occurs. , that is, when trying to ignite thyristor Th2 and extinguish thyristor Thl, the charging/discharging current 12
, i1 becomes small, and the commutation ability decreases. For this reason, inverters with such variable loads must be equipped with capacitors of large capacity that are not needed during normal operation.
This has caused the volume of the inverter to increase and the efficiency to decrease. The third drawback is that during commutation, that is, during the period when the charging and discharging currents 11 and 12 are flowing, a voltage equal to the sum of the DC power supplies E1 and E2 is applied to the transformer T.

Therefore, an exciting current 1T comes to flow through this transformer T, and in order to keep this exciting current 1T small, the exciting inductance must be made large. Therefore, the transformer T becomes large. Further, the discharge current, for example i1, is caused by the difference between the voltage of the capacitor σ and the induced voltage generated in the winding of the transformer T, and due to this induced voltage, the voltage of the capacitor is not used effectively. This also requires a capacitor with a large capacity. In order to eliminate these drawbacks, the present invention replaces the conventional thyristor with two thyristors in series to suppress the voltage applied to the load and prevent capacitor discharge from occurring at times other than commutation. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a first embodiment of the inverter of the present invention.

Thyristors Thl and Th2 in the conventional example shown in FIG.
Two sets of thyristor circuits Th, l-Thl2 and Th2l-Th2 each having two thyristors connected in series.
2 and the transformer T is replaced by two reactors 11 and 12. That is, a thyristor circuit A is formed in which two thyristors Th, l, Th, and 2 are connected in series, and a thyristor circuit B is formed in which thyristors Th2l and Th22 are connected in series.
Reactor 1 is connected to the cathode of thyristor Thl2 that constitutes
One terminal of the reactor 12 is connected to the anode of the thyristor Th2 constituting the thyristor circuit B, and the reactors '1 and 12 are connected in series, and the series connection point P and the load are connected to one terminal of the reactor 12. Connect one terminal of Z,
The other terminal of load Z is connected to the connection point between DC power supplies E1 and E2. Both ends of the series circuit of capacitors C1 and C2 are connected to a connection point between thyristors Thll and Thl2 and a connection point between thyristors Th2l and Th22, respectively. The diodes Dl and D2 are each connected to a thyristor Thl2.
, Th2l in antiparallel. One terminal of the reactor L is connected to the series connection point P of the reactors 1, 12, and the other terminal is connected to the connection point of the capacitors C, , C2. In addition, the anode of the thyristor Thll is connected to the positive electrode of the DC power source E1, and the cathode of the thyristor Th22 is connected to the positive electrode of the DC power source E1.
Connect to the negative terminal of 2. Now, the thyristor Thll, Th,
2 is energized and in a steady state.

At this time, the load Z is connected to the DC power supply E and the thyristor Thl.
A current 12 is flowing through the route of the reactor 11. It is also assumed that the voltage of capacitor C1 is zero, and that capacitor C2 is charged to a higher level than DC power source E2 with the polarity shown in the figure. At this time, when thyristor Th2l is turned on to extinguish thyristors Thll and Thl2, capacitor C
The charge stored in 2 is discharged in two loops.

One is a loop of reactors L, l2, and thyristor Th2l that generates current 13, and the other is a loop of capacitor Cl, thyristor Thl2, reactors 1, 12, and thyristor Th2.
A current 14 is produced in the loop of l.

These currents 13 and I4 are series resonant currents, and as time passes, the connection point side of the capacitor C1 with the capacitor C2 is positively charged, and when it reaches its maximum value, the current 14 becomes zero.
Next, capacitor C1 is connected to reactor L, ll, diode D
1 and the loop of capacitor C2, diode D2, reactors 12, 11, and diode D1, producing currents 15 and I6, respectively. These currents 15 and I6 are also series resonant currents, and the voltage of the capacitor C decreases over time, and then is charged to the opposite polarity. Even after the current 1, +I6 flowing through the diode D1 becomes zero,
The current 1z flowing through the load Z is the DC power supply El and the thyristor T.
h,, in the loop of capacitor C, reactor L, and load Z, the voltage of flow capacitor C1 becomes higher than the level of DC power source E1. While the current 15, i6 is flowing through the diode D1, its forward voltage drop (approximately 1 volt in the case of a silicon diode) reverse biases the thyristor Thl2 and extinguishes it. When the capacitor C is charged to a level higher than the level of the DC power source E1 and the current 1z flowing through the load Z becomes zero, the thyristor Th,l is also extinguished. When the thyristors Th2l and Th22 are ignited after an appropriate time has elapsed, a current with the opposite polarity to the current 1z flows through the loop of the DC power supply E2, the load Z, the reactor 12, and the thyristors Th2l and Th22.

After energizing thyristors Th2l and Th22 for a certain period of time, when thyristor Thl2 is fired, capacitor C
, the charges stored in thyristor Th,2 and reactor 1
1, L loop and thyristor Thl2, reactor 1,,
22, the loop of the thyristor Th2l and the capacitor C2 is discharged, and the capacitor C2 is charged with the opposite polarity to the direction shown in the figure. When the voltage of capacitor C2 reaches its maximum value, the charging current becomes zero. Then capacitor C2 is connected to diode D2
, reactor 12, L, and a loop of diode D2, reactors 12, 11, diode Dl, and capacitor C1. The voltage of the capacitor C2 becomes zero as time passes, and is further charged in the direction shown in the figure. Even after the current flowing through diode D2 becomes zero, the current flowing through load Z continues to flow through the loop of DC power supply E2, load Z1, reactor L1, capacitor C2, and thyristor Th22, and the voltage of capacitor C2 is lower than the level of DC power supply E2. It gets expensive.

While current is flowing through the diode D2, its forward voltage drop (approximately 1 volt in the case of a silicon diode) acts as a reverse bias on the thyristor Th2l, extinguishing it. When the capacitor C2 is charged higher than the level of the DC power source E2 and the current flowing through the load Z becomes zero, the thyristor Th22 is also turned off. Next, when the thyristors Th, l, and Thl2 are ignited after an appropriate time, a current 1z flows through the loop of the DC power supply E, the thyristors Th, l, and Thl2, the reactor 11, and the load Z, returning to the initial state. In this way, in the inverter of the present invention, the thyristors Thll and Th,
When the thyristors Th2l and Th22 are energized at the same time, a current 1z flows through the load Z, and when the thyristors Th2l and Th22 are energized at the same time, a current with the opposite polarity to Iz flows through the load Z.

In other words, AC power is applied to the load Z. Also, thyristors Th,l and Th,2 (or Th2l and Th22)
Since no current flows through the load Z during a period in which both are not energized at the same time, the effective power given to the load is adjusted by controlling the ratio between the non-energized period and the energized period. That is, the present invention is equipped with a control function. Furthermore, since the present invention does not have a large transformer, the device is compact and highly efficient.
Further, in the present invention, for example, thyristors Thll and Thl2
is energized and current 12 is flowing through load Z, thyristors Th2l and Th22 are not energized, so the charge in capacitor C2 is held without being discharged. Therefore, even if the load Z suddenly becomes heavy and the current 1z increases rapidly, the charge in the capacitor C2 is not lost, so that the next commutation can be carried out effectively. That is, unlike the conventional example, there is no need to provide a large capacitor that is not needed on a regular basis, and the inverter is therefore smaller and more efficient. Further, in the present invention, a large resonant current flows through the diodes Dl and D2 when they try to extinguish the thyristors Thl2 and Th2, which are connected in antiparallel to each other.

Therefore, the capacitances of capacitors Cl and C2 can be equivalently reduced. As explained above, according to the present invention, it is possible to control the period during which the load is not energized, no transformer is required, and the capacitance of the capacitor can be small. can get.

[Brief explanation of the drawing]

FIG. 1 shows an example of a conventional inverter, and FIG. 2 shows a first embodiment of the inverter of the present invention.

Claims (1)

[Claims] 1 The third thyristor Th_1 is connected to the first DC power supply E_1.
_1, the first thyristor Th_1_2, the second reactor l_1 and the load Z are connected, and the third reactor l_2, the second thyristor Th_2_1 and the fourth thyristor Th_2_2 are connected to the second DC power supply E_2 via the load. A first diode D_1 and a second diode D_2 are connected in antiparallel to the first and second thyristors, respectively, and a first capacitor C_1 is connected across the first thyristor and the second reactor. Connect the first reactor L,
A thyristor inverter characterized in that a second capacitor C_2 is connected to both ends of the third reactor and the second thyristor via the first reactor.