JPS6412187B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thyristor inverter device, and particularly in a self-excited thyristor inverter device equipped with a feedback diode, the current change rate di/at the rise and fall of the current flowing through the main thyristor and the feedback diode. The aim is to protect these elements by suppressing dt.

The first thyristor inverter device of its kind.
There is a configuration as shown in the figure. In Figure 1, when the main thyristor M _p is fired, the DC power supply
E ₁ - Main thyristor M _p - Reactor L ₃ - Load Z -
A voltage e ₀ of the illustrated polarity is applied from the DC power source E ₁ to the load Z through the loop of the DC power source E ₁ . While this main thyristor M _p is energized, the auxiliary thyristor
A _N is turned on, and the commutating capacitor C is connected through the loop of DC power supply E ₂ - E ₁ main thyristor M _p - reactor L ₃ - capacitor C - reactor L ₂ - auxiliary thyristor A _N - DC power supply E ₂ . V _c = E ₁ with the polarity shown
Charge only the value of +E ₂ . Note that the commutating capacitor C is charged by the main thyristor M _p and the auxiliary thyristor A _N only during the first half cycle at startup.

Next, to turn off the main thyristor M _p , the auxiliary thyristor A _p is turned on. As a result, the current in the main thyristor M _p decreases due to the charging voltage V _c of the commutation capacitor C, the current in the auxiliary thyristor A _P increases, the load current commutates to the auxiliary thyristor A _p side, and finally the main Thyristor M _p is turned off.

If the reactors L ₁ and L ₃ are now magnetically coupled and the number of turns of each is chosen to be equal, commutation is instantaneously effected by firing of the auxiliary thyristor A _p .

Hereafter, DC power supply E ₁ - Auxiliary thyristor A _p - Reactor L ₁ - Commutation capacitor C - Load Z - DC power supply
The commutating capacitor C is discharged through the loop of E ₁ , and if the load is inductive or light, the auxiliary thyristor A _p - reactor L ₁ - commutating capacitor C
−Reactor L ₄ −Feedback diode D _p −Reactor L ₁ , L ₄ by the loop of auxiliary thyristor A _p
A part of the energy stored in capacitor C is transferred to . When the voltage of the capacitor C eventually becomes zero, the energy stored in the reactors L ₁ and L ₄ is transferred to the auxiliary thyristor A _p -reactor L ₁ -
Capacitor C - Reactor L ₄ - Feedback diode
Through the loop of D _p - auxiliary thyristor A _p the commutating capacitor C is reverse charged, or auxiliary thyristor A _p - reactor L ₁ - commutating capacitor C - load Z - DC power source E ₁ - auxiliary thyristor A _p Capacitor C is charged through the loop. At this time, the capacitor C is charged to V _c =E ₁ +E ₂ with a polarity opposite to that shown in FIG.

The lagging current of the inductive load is then fed back to the feedback diode.
Power is fed back through a loop of D _N - reactor L ₃ - load Z - DC power supply E ₂ - feedback diode D _N.

Thereafter, when the second main thyristor M _N is fired, reverse polarity power is supplied to the load, and the same operation is repeated thereafter.

By the way, if we examine the current waveform of each element during each commutation mentioned above, it will be seen that each element has the following responsibility as the current change rate di/dt.

Figures 2 and 3 show waveforms for lagging loads, where the load voltage e ₀ (A in Figure 2) is equal to the load current i ₀
(FIG. 2B) changes polarity when commutated from the main thyristor element M _p or M _N to the feedback diode D _N or D _p . However, if we further expand and look _in detail at the changes in the commutation state of the load current i ₀ in FIG. 2B, as shown in _FIG . Subsequently, the current is commutated from the auxiliary thyristor A _p to the feedback diode D _N.
That is, when the auxiliary thyristor A _p is fired at time t ₁ , the current flowing through the main thyristor M _p is commutated to the auxiliary thyristor A _p . The time T ₁ required for commutation is determined by the leakage reactance of the coupling of reactors L ₁ and L ₃ in Figure 1, and the charging voltage of commutation capacitor C is determined by E and the leakage reactance of the coupling of reactors L ₁ and L ₃ . Assuming that the charging voltage of commutating capacitor C is E, the coupling leakage reactance of reactors _L1 and _L3 is _Ll , and the main circuit current peak value (commutating current) is _Ip , then E
= L _l di/dt, T ₁ ≒ I _p L _l /E. As described above, in the delayed load, the main thyristor M _p is responsible for the falling of di/dt = I _p /T ₁ , and the auxiliary thyristor A _p is responsible for the rising of di/dt = I _p /T ₁ and di /dt=I _p /T ₂ is responsible for the falling edge, and the diode D _N is also responsible for the rising edge of di/dt=I _p /T ₂ .

Also, load voltage e ₀ and load current in case of leading load
i ₀ corresponds to A and B in Fig. 4, A and B in Fig. 4.
As shown in , the load current i ₀ is connected to the feedback diode D _p or
When commutating from D _N to main thyristor M _N or M _p ,
The load voltage e ₀ changes polarity, but in the case of this leading load voltage, it is directly transferred from the diode D _N to the main thyristor M _p without going through the auxiliary thyristor, as shown in FIG. The flow is carried out. The commutation time T ₃ at this time is determined by the reactance value included in the loop of DC power source E ₁ -main thyristor M _p -feedback diode D _N -DC power source E ₂ -E ₁ in FIG. However, since this loop only has reactance due to the wiring, the main circuit current change rate di/dt has a very large value.

After all, in the case of a leading load, the diode D _N has
The main thyristor M p is responsible for the falling of di/dt=I _p /T ₃ , and the main thyristor M _p is responsible for the rising of di/dt=I _p /T ₃ .

Furthermore, the load voltage e ₀ in the case of no load is shown in FIG. 6, corresponding to FIG. 2A, and the change in the commutation state of the no-load current is shown in FIG. 7, corresponding to FIG. 3A.

That is, if the auxiliary thyristor A _p is turned on at time t ₇ , the accumulated charge in the commutating capacitor C is reduced to the commutating capacitor C - reactor L ₄ - feedback diode in Fig. 1.
It flows through the loop of D _p -main thyristor A _p -reactor L ₁ and vibrates in a resonant circuit consisting of the capacitance of commutating capacitor C and the sum of the reactances of reactors L ₁ and L ₄ .

Then, at time t ₈ , when the thyristor M _N is ignited, the commutating capacitor C - reactor L ₄ - diode D _p
- Auxiliary thyristor A _p - The current flowing through the loop of reactor L ₁ is the capacitor C - Reactor L ₄ - Main thyristor M _N - DC power supply E ₂ - E ₁ - Auxiliary thyristor A _p - Loop of reactor L ₁ transfer to. The commutation time T ₄ at this time is determined by the reactance value included in the loop of DC power supply E ₁ - diode D _p - main thyristor M _N - DC power supply E ₂ - _{E 1} in Figure 1. Since there is only reactance due to Therefore, in the case of no load, the diode
D _p is responsible for the fall of di/dt=I _M ′/T ₄ , and the main thyristor M _N is responsible for the rise of di/dt=I _M ′/T ₄ .

In this way, in the thyristor inverter device having the configuration shown in FIG. 1, the semiconductor elements of the main thyristor, auxiliary thyristor, and feedback diode are responsible for the steep rise and fall of the current. However, if a semiconductor device has a steep rising current rate of change during ignition, the device will be destroyed because the gate will not expand sufficiently. Furthermore, if there is a steep falling current change rate when the current is turned off, the reverse recovery charge Q r will rise as shown in Figure 8B, and the reverse recovery charge Q _r will be larger than when the fall is gentle (Figure 8A). Therefore, when devices are connected in series as shown in FIG. 9, voltage unbalance becomes large. When the reverse circuit charge Q _r increases, the capacitor shown in Figure 9 is used to absorb it.
It is necessary to select a _CA with large capacity.

In order to solve this problem, conventionally, as shown in Fig. 10, a coil is wound around a saturable magnetic core, such as a ferrite core, between the main thyristor _Mp and the reactor _L3 , and the current in the coil is smaller than the current _IP . A saturable reactor (hereinafter referred to as a ferrite core) _Fp that is magnetically saturated above a certain value is inserted, and a ferrite core _FN is similarly inserted between the main thyristor _MN and the reactor _L4 . According to this configuration, in the case of a lagging load, the falling waveform of the main thyristor M _p and the rising waveform of the auxiliary thyristor A _p can be compensated by the ferrite core F _p as shown in FIG. 11A in correspondence with FIG. 3A. . In the case of a leading load, the rising waveform of the main thyristor M _p and the falling waveform of the diode D _N can be compensated by the ferrite core F _p as shown in FIG. 11B corresponding to FIG. 5. Furthermore, in the case of no load, the rising waveform of the main thyristor M _N and the falling waveform of the diode D _p can be compensated by the ferrite core F _N as shown in FIG. 11C corresponding to FIG.

By the way, the ferrite core with the configuration shown in Figure 10
Waveform compensation by F _p and F _N is effective for the main thyristor because it can significantly reduce the rate of change in current, but it remains insufficient for the feedback diode.

In consideration of the above points, in the present invention, the number of ferrite cores is the same as the conventional case shown in FIG. The aim is to make it possible to achieve the following.

An example of the present invention will be described in detail below with reference to the drawings.
The thyristor inverter device according to the present invention is the tenth
As shown in FIG. 12 with the same reference numerals assigned to corresponding parts, in FIG. 10 the main thyristor M _p and
Ferrite core F _p inserted in the arm of M _N and
Omit F _N and replace it with the connection point of the main thyristor M _p and feedback diode D _p , and the auxiliary thyristor
A ferrite core F _p is inserted between the contact point of A _p and the DC power source E ₁ , and similarly the connection point of the main thyristor M _N and feedback diode D _N and the connection point of the auxiliary thyristor A _N and the DC power source E ₂ . ferrite core between
It has the same configuration as _FN inserted.

In the configuration shown in Fig. 12, in the case of lagging load, the first
As shown in Figure 13A corresponding to Figure 1A, the time point
When the auxiliary thyristor A _p is fired at t ₁ , commutation from the main thyristor M _p to the auxiliary thyristor A _p starts, and when the main thyristor current approaches 0, the ferrite core F _p is reset, and the current of the main thyristor M _p The falling di/dt of becomes small. Furthermore, when commutating from the auxiliary thyristor A _p to the diode D _N , the ferrite core F _N acts in the same way, and the di/dt of the current rise in the diode D _N becomes small.

On the other hand, in the case of a leading load, as shown in FIG. 13B corresponding to FIG. 11B, and in the case of no load, as shown in FIG. 13C corresponding to FIG. 11C,
It is possible to reduce di/dt not only for the main thyristor current but also for the falling waveform of the feedback diode current.

As described above, according to the present invention, it is possible to suppress both the rise and fall of the current in the main thyristor and the feedback diode with the same number of ferrite cores as in the past, and therefore the inverter device can be controlled without destroying the semiconductor elements. Therefore, the value of the surge absorber capacitor can be reduced.

In the case of the embodiment shown in FIG. 12, the present invention is applied to a single-phase thyristor inverter device, but even if the present invention is applied to a three-phase thyristor inverter device as shown in FIG. The same effect can be obtained as in the case of . In the embodiment of the present invention, the main thyristors M _P and M _N are the first main thyristor and the second main thyristor, respectively, and the auxiliary thyristors A _P and A _N are the first main thyristor, respectively.
an auxiliary thyristor and a second auxiliary thyristor,
Reactors L ₃ and L ₄ are connected to the first reactor and second reactor, respectively, and reactors L 1 and L ₄ are connected to the first reactor and second reactor, respectively.
L ₂ corresponds to a third reactor and a fourth reactor, respectively, and feedback diodes D _P and D _N correspond to a first feedback diode and a second feedback diode, respectively.

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing a self-excited thyristor inverter device equipped with a feedback diode to which the present invention can be applied, and Figs. 2 to 9 are signal waveform diagrams, curve diagrams, and partial circuit diagrams to explain its operation. , 10th
The figure is a connection diagram showing a conventional thyristor inverter device, FIG. 11 is a signal waveform diagram for explaining its operation, FIG. 12 is a connection diagram showing an example of a thyristor inverter device according to the present invention, and FIG. 13 is its operation. FIG. 14 is a connection diagram showing an application example of the thyristor inverter device of FIG. 12. E ₁ , E ₂ , E: DC power supply, M _p , M _N : main thyristor, A _p , A _N : auxiliary thyristor, D _p , D _N : feedback diode, L ₁ , L ₄ : reactor, Z: load, _Fp ,
F _N : Saturable magnetic core (ferrite core).

Claims (1)

[Claims] 1 DC power supply, first and second main thyristors connected across both ends of this DC power supply and connected in series to each other, first and second auxiliary thyristors respectively connected in parallel to these main thyristors, A commutating capacitor inserted between the connection point of the first and second main thyristors and the connection point of the first and second auxiliary thyristors, respectively first and second reactors connected in series and magnetically coupled to each other; third and fourth reactors connected in series to the second main thyristor and second auxiliary thyristor and magnetically coupled to each other, respectively; A reactor, one end connected to one end of the first main thyristor and the other end connected to the second main thyristor and the third main thyristor.
a first feedback diode connected to a connection point with the reactor, one end of which is connected to one end of the second main thyristor, and the other end connected to a connection point of the first main thyristor and the first reactor; a second feedback diode, a first saturable magnetic core provided between a connection point between the first main thyristor and the first feedback diode and one end of the DC power supply, and a second main thyristor. and a second saturable magnetic iron core provided between a connection point between the first and second feedback diodes and the other end of the DC power supply;
A thyristor inverter device in which alternating current output is taken out from a series connection of these main thyristors by alternately conducting the main thyristors.