JPS5835362B2 - dc transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC transformer, and more particularly to a DC transformer suitable for good operation even when the polarity of the primary current to be detected changes suddenly.

FIG. 1 is an example of a known DC transformer composed of two saturable reactors.

A secondary winding 13, 14 is wound on each of the saturable cores 11 and 12 passed through the primary conductor 10.

These two secondary windings 13 and 14 are differentially connected in series,
Furthermore, an AC power supply 15, a full-wave rectifier circuit 16, and an output load 17
are connected in series to form a closed circuit and constitute a secondary circuit.

FIG. 2 shows the operating waveforms of each part of the above-mentioned constituent circuit.

- In contrast to the DC current flowing through the secondary conductor 10, the two saturable reactors repeat saturation and non-saturation states every half cycle of the AC power supply, so the voltage at both terminals of the secondary winding 13°140, V2 is As shown in the figure, it becomes part of a sine wave, and the secondary winding (2) at this time has a substantially square wave shape.

Therefore, the output load 17 receives a current of 0.05 to 1.0 volts and operates as a DC transformer.

In the DC transformer shown in Fig. 1, the polarity of the DC current wire of the -order conductor 10 is reversed, and when the impulse current or the primary power supply current is turned on and off, the two parts forming the DC transformer are In some cases, two saturable reactors become unsaturated at the same time.

As shown in FIG. 3, the equivalent circuit of the DC transformer at this time is a parallel circuit consisting of an exciting inductance 30, a resistance 31 caused by an eddy current in the iron core, and a capacitance 32 between the secondary windings.

At this time, when the DC current (1) of the -order conductor 10 suddenly changes as described above and the two saturable reactors constituting the DC current transformer become unsaturated at the same time, the exciting inductance 30 and the eddy current resistance 31 of the iron core is extremely large due to the non-saturation of the iron core, and the secondary winding voltage 33 has the problem that an excessive voltage is generated due to the current that charges up the capacitance 32 between the secondary windings.

Conventionally, as a method for suppressing excessive voltage in the secondary winding 13.14 of a DC transformer consisting of at least two saturable reactors, a protection device is installed in parallel with the secondary winding 13.14 as shown in FIG. 40, a method for connecting, for example, a C-R absorber or nonlinear element.

In addition, as another example, as shown in FIG. 5, as a countermeasure against overvoltage in the secondary windings 13 and 14 due to the steep current change d i / d t of the primary current A protection device 40, for example, a method in which nonlinear rectifying elements are connected in antiparallel, is generally known.

In the conventional embodiment shown in FIG.
1 is a system in which the protection device 40 operates in a state where excessive voltage is generated in the secondary winding 13.14 when the voltage suddenly changes, and fundamentally suppresses the excessive voltage generated in the secondary winding 13.14. It's not a thing.

Furthermore, in this method, when an excessive voltage is generated in the secondary winding 13, 14, that is, when two saturable reactors are simultaneously unsaturated, the saturable iron cores 11, 120B-H constituting the saturable reactor Due to the difference in characteristics, a voltage is generated in the secondary winding differential voltage section, and its influence appears on the terminal of the output load 1T in the subsequent stage, causing problems such as malfunction as a DC transformer.

Furthermore, in the conventional embodiment shown in FIG.
A nonlinear element, such as a rectifier, is connected in antiparallel to both terminals as a protection device 40, and the -order current (2) is shunted to the rectifier, which may cause problems in detection accuracy.
Furthermore, since the protection device 40 is provided in the primary current circuit on the high voltage side, it has drawbacks such as requiring a high withstand voltage device.

The object of the present invention is to provide a DC transformer that can suppress the excessive voltage generated at both terminals of the secondary winding when the -order current (1) suddenly changes. It is on offer.

The present invention provides a DC transformer formed by forming a closed circuit with an AC power source 15, a full-wave rectifier circuit 16, and an output load 17, two saturable reactors that penetrate a -order conductor or have a -order winding. As a method of suppressing excessive voltage from being generated at both terminals of the secondary winding when the negative secondary current ■1 changes suddenly, the saturable reactor is newly arranged in a harmonic manner with respect to the negative secondary winding. A closed circuit is constructed using a suitable impedance element, and this tertiary winding circuit has the effect of a short-circuit winding.

FIG. 6 shows an embodiment of the present invention.

In FIG. 6, the two saturable reactors penetrating the -order conductor and the closed circuit forming the secondary winding thereof have the same reference numerals as those described in the prior art, and the explanation thereof will be omitted.

In FIG. 6, two iron cores it, 12 penetrating the primary conductor 10
The secondary winding 13.14 is differentially wound in series on the negative conductor 10, and the tertiary winding 18.1 is arranged in a harmonic manner.
The tertiary winding circuit, which constitutes a closed circuit with 9 and the resistor 20, is a short-circuit winding circuit for suppressing excessive voltage generated in the secondary windings 13 and 14.

The DC transformer having the above-mentioned tertiary winding circuit has a negative order conductor 1
When a steady current 1 is flowing at 0, only the even harmonic current of the saturable reactor flows, and there is no particular problem in the operation of the DC transformer.

In a DC transformer with this tertiary winding circuit, if the primary current (1) suddenly changes and the two saturable reactors become unsaturated at the same time, the DC transformer's equal circuit will become as shown in Figure 7. Become.

In other words, this time the secondary winding of the saturation reactor is 13°140
If the number of turns is N2, the number of turns N3 of the tertiary windings 18 and 19, and the tertiary winding load resistance 20 is R3, then the tertiary winding load resistance R3 was converted to the secondary winding side using the relationship in equation (1). However, the load resistance 35 of the tertiary winding converted to the R3' secondary winding side is connected in parallel.

This equivalent conversion resistor 35 limits the current 34 flowing to the secondary winding when the current 1 in the primary conductor of the DC transformer changes suddenly, thereby suppressing excessive voltage.

As another embodiment of the present invention, as shown in FIG. 8, a resistor 20 is connected to a circuit formed by winding the tertiary winding 18 of a saturable reactor commonly around two iron cores 11 and 12. has a similar effect.

Furthermore, this method also has the advantage of reducing the manufacturing cost of the DC transformer.

Further, as another embodiment, the same effect can be obtained when nonlinear elements such as Zener diodes 21 and 22 are connected in forward and reverse series to the tertiary winding circuit of the saturable reactor as shown in FIG.

Furthermore, as another embodiment, as shown in FIG.
A similar effect can also be obtained by adding .

[Brief explanation of drawings]

Figure 1 is an example of a conventional DC transformer consisting of two saturable reactors, Figure 2 is an example of the operating waveforms of the main parts of the conventional DC transformer shown in Figure 1, and Figure 3 is an example of the operating waveforms of the main parts of the conventional DC transformer shown in Figure 1. The equivalent circuit of a DC transformer when the two saturable reactors that make up the DC transformer shown in the figure become unsaturated at the same time, Figures 4 and 5 are composed of two conventional saturable reactors. A circuit diagram showing an embodiment of suppressing excessive voltage generated in a secondary winding when a sudden change in secondary current occurs in a DC transformer, FIG. 6 is an embodiment of a DC transformer having a tertiary winding according to the present invention, Fig. 7 is an equivalent circuit diagram of the DC transformer when the two saturable reactors of the DC transformer having the tertiary winding shown in Fig. 6 become unsaturated at the same time, and Figs. 8 to 10 is an example of a DC transformer showing another embodiment of the present invention. 10... -order conductor or primary winding, 11.12...
Saturable iron core, 13.14... Secondary winding, 15... AC power supply, 16... Full wave rectifier circuit, 17... Output load, 18.19... Tertiary winding, 20... ...Resistance, 21~
24... Zener diode, 25... Current limiting resistor,
30... Excitation inductance, 31... Resistance due to eddy current of iron core, 32... Capacitance between secondary windings, 33
...Secondary winding voltage, 34...Secondary current, 35...
Tertiary winding circuit resistance in terms of secondary winding, 40...Protective device.

Claims (1)

[Claims] At least two or more saturable reactors each having a primary winding and a secondary winding are used, and the secondary windings of the saturable reactors are differentially connected in series, and other differentially connected In a DC transformer comprising an AC power supply and a load forming a closed circuit at the output terminal section, the two saturable reactors include a tertiary winding arranged in harmony with the secondary winding, and the tertiary winding. A DC transformer characterized by having impedance elements at both terminals of the line.