JP2000341952A - Ultralow-frequency high voltage power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance, such as miniaturization of a device and the reduction of input capacity. SOLUTION: In a full wave twofold voltage rectifying circuit, two rectifying circuits, where modulation voltage by the reference power source 11 (0.1 Hz) of an AC switching regulator 2 is applied to the primary side of a high voltage transformer 3 from a commercial frequency power source 1, two pairs of rectifying elements which are connected to reverse polarities in series are connected to a secondary side in parallel, the intermediate points are connected to high voltage semiconductor switches 25 and 26 are installed, and each piece end is connected to one end of a secondary wire and the other end is set to be output. The gate signals of the two high voltage semiconductor switches 25 and 26 are as signals via the AND circuits 5, 6, 8 and 9 and OR circuits 7 and 10 of the respective synchronizing signals of a commercial frequency and a reference power frequency. They are transmitted alternately at every inversion of the polarity of commercial frequency voltage and ultralow-frequency voltage following the increase/decrease of reference voltage is generated through the full wave double voltage rectifying circuit and a smoothing circuit with the conduction operation of the high voltage semiconductor switches 25 and 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-low frequency power supply used for a dielectric strength test of a high-voltage device, particularly a power cable.

[0002]

2. Description of the Related Art In an AC dielectric strength test of a high-voltage device or a power cable, if the capacitance is large, the load current is large and the capacity of a test power supply is very large. The external weight was not economical due to problems in its transportation and the like. Therefore, a DC test has been generally performed instead of the AC test. However, since the electric field distribution in the insulator when a DC voltage is applied is different from that when an AC voltage is applied, it was questioned whether defects in the insulator could always be detected by applying a DC voltage. In addition, it was feared that a DC insulator might damage a sound insulator. Therefore, in order to perform the original AC test, various methods for reducing the capacity of the apparatus by setting the frequency to about 0.1 Hz and reducing the capacity have been considered. For example, a method is introduced in which a commercial frequency power supply is amplitude-modulated by a sliderac that is synchronized to an ultra-low frequency, the voltage is boosted by a high-voltage transformer, and an ultra-low-frequency voltage that follows the envelope of the modulation voltage via a rectifier circuit is introduced. Have been.

[0003]

However, the above-mentioned method of driving the SLIDAC at an extremely low frequency and modulating the amplitude of the commercial frequency voltage has the following disadvantages.

There are problems with mechanical mechanisms and power for mechanically driving the SLIDAC, waveform distortion due to poor contact of slide points, and life due to spark generation.

When the output voltage is increased to the maximum and then decreased, the electric charge charged in the capacitance of the device under test must be discharged. Must be connected in parallel with the test object,
There is a drawback that the capacity of the device is increased accordingly.

In order to generate an AC output voltage, the polarity of the rectifier circuit must be inverted every half cycle, and a switch for inverting the diode of the rectifier circuit is required.
In particular, when the output voltage is high, this causes an increase in the size of the device in withstanding voltage.

[0007]

SUMMARY OF THE INVENTION The present invention provides a compact and economical device by using an AC switching regulator, a semiconductor device and the like and control electronics thereof, instead of using the above-mentioned slidac. Things. The basic means are as follows.

An input is a commercial frequency power supply, and an AC switching regulator is used in place of a slidac for voltage adjustment. The voltage adjustment is performed by an ultra-low frequency generation reference power supply (hereinafter referred to as a reference power supply) connected to a control input of the regulator. A modulation voltage is generated by voltage adjustment.

The voltage is boosted by a high-voltage transformer having a secondary winding having both ends, and the secondary high-voltage side is constituted by a full-wave double voltage rectifier circuit using a rectifying element and a high-voltage semiconductor switch. The gate signal uses the AND signal of the synchronizing signal of the power supply frequency and the reference power supply frequency. The same signal is transmitted alternately to the gate terminals of the above two switches every time the polarity of the commercial frequency power supply is inverted, and follows the reference voltage. The charged voltage is generated to charge and discharge the capacitance of the device under test.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a basic circuit diagram of the present invention, and FIG.
Indicates the operation waveform of each unit. 1 and 2, the voltage E1 of the commercial frequency power supply 1 (50 or 60 Hz) is transmitted to the input of the AC switching regulator 2, and the reference power supply 11
(0.1 Hz) The output modulation voltage by the control voltage of the voltage E2 is connected to the primary side of the high-voltage transformer 3, and the high-voltage secondary voltage (dotted line in FIG. 2) is applied to the secondary windings insulated at both ends. generate.
At the same time, the voltage of E1 is connected to the synchronization circuit 4 to generate synchronization signals P1 and P2 synchronized with the commercial frequency with a fixed width centered on the positive and negative peak values of E1. Further, the synchronizing circuit 12 generates the synchronizing signal P3 during the positive generation of the reference voltage E2 and the synchronizing signal P4 during the negative generation, and generates P1 and P3, P2 and P4, P
AND signals of P2 and P3 and P1 and P4
Through circuits 5, 6, 8, and 9, the synchronization signals 1P, 4P,
2P and 3P are generated. Next, 1P and 4P, 2P and 3P are connected to the high voltage semiconductor switch 2 through OR circuits 7 and 10.
5, 26 gate signals G1 and G2 are generated.

On the other hand, two rectifying elements 13 and 15, 14 and 16, and 17 and 19, 1
8 and 20 are formed in parallel, and the intermediate points of each of them are connected to high-voltage semiconductor switches 25 and 26 and protection resistors 21 and 22.
Two sets of rectifier circuits connected by a series circuit of 23 and 24 are provided, one end of which is connected to one end of a secondary winding of the high voltage transformer, the other end is connected in series, and one end is connected to one end of smoothing capacitors 27 and 28. And one end of the secondary winding is connected to a capacitor 27, 2
A double voltage rectifier circuit is formed by connecting to the intermediate point of No. 8 and a voltage twice as high as the peak value of the secondary voltage is generated between the capacitors.

Next, the operation function will be described with reference to FIGS.
The waveform of the secondary voltage generated by the high voltage transformer 3 modulated by the reference power supply 11 and the AC switching regulator 2 corresponds to the waveform of the reference voltage E2 (0.1 Hz) as shown by the dotted line in FIG. Rises to the positive side from zero, the secondary voltage also rises from zero to a modulated voltage as shown by the dotted line. Now, the voltage at one end of the secondary winding connected to the rectifiers 13, 16 and 17 and 20 is
When the polarity is positive with respect to the other end connected to the middle point of the rectifier circuit and the gate signal G1 of the synchronizing signal 1P, the high-voltage semiconductor switch 25 becomes conductive, and the current of the secondary voltage is reduced by the rectifier element 13 and the protection resistor 21. Flows through the high-voltage semiconductor switch 25, the protection resistor 22, the rectifying element 14, and the smoothing capacitor 27 to charge the smoothing capacitor 27 and
A voltage E3 corresponding to the peak value of the next voltage is
Occur at both ends. In the next half cycle, the rectifying element 13,
The polarity of the voltage of the secondary winding connected to 16, 17, and 20 is inverted and becomes negative, and the high-voltage semiconductor switch 26 is turned on by the rectifier circuit and the gate signal G 2 of the synchronization signal 2 P in the same operation as in the case of positive polarity. The secondary current flows through the smoothing capacitor 28, the rectifying element 18, the protection resistor 24, the high-voltage semiconductor switch 26, the protection resistor 23, and the rectifying element 17, and charges the smoothing capacitor 28 to thereby charge the secondary voltage. , A voltage E4 corresponding to the peak value is generated across the capacitor 28. Note that the polarity of E3 and E4 is
The connection points 7 and 28 have opposite polarities, but have the same polarity with respect to ground as shown in FIG. 1, and the ground voltage is E3 + E.
4 and E3 = E4, which is twice the peak value of the secondary voltage. Thus, the voltages E3 and E4 which are charged alternately every half cycle and follow the envelope of the secondary peak voltage are generated and rise as the reference voltage rises. Next, when the secondary voltage exceeds the peak value, the voltage becomes lower than the charging voltages E3 and E4, and the voltage E3 of the smoothing capacitor 27 is changed every half cycle by the gate signals G1 and G2, so that the rectifying element 15, the protection resistor 21, the high-voltage semiconductor switch 25, The current is discharged through the protection resistor 22, the rectifier 16 and the secondary winding of the high-voltage transformer 3 until the peak value of the secondary voltage at that time is reached. In the next half cycle, the voltage E4 of the smoothing capacitor 28 is also changed to the voltage of the rectifier 19, the high-voltage semiconductor switch 26, the rectifier 20 and the high-voltage transformer 3
Through the next winding, the secondary voltage is discharged until the peak value of the secondary voltage at that time is reached, and as with the rising, the voltage drops with the waveforms E3 and E4 following the envelope of the peak value as the secondary modulation voltage falls.

Next, when the polarity of the reference voltage E2 shifts to negative, the rectification operation of E3 and E4 by the secondary voltage of the high-voltage transformer 3 is performed alternately every half cycle, as in the case of positive. , G2 high voltage semiconductor switches 25, 26
During the period in which the secondary voltage is from zero to a negative peak value due to the conduction operation of the high voltage transformer, the secondary current of the high voltage transformer is
The current flows through the capacitor 27, the rectifier 15, the protection resistor 21, the high-voltage semiconductor switch 25, the protection resistor 22, and the rectifier 16 via the middle point between the high-voltage transformer and the high-voltage transformer in the next half cycle. Each circuit element 1 from the other end of
7, 23, 26, 24, 18, and 28, the voltages E3 and E4 corresponding to the peak value of the secondary voltage are charged on the high voltage side of the smoothing capacitors 27 and 28, and the negative voltage of E3 + E4 as a ground voltage. Occurs. Next, during the period when the secondary voltage is zero from the peak value, the smoothing capacitors 27, 2
8 are applied to the circuit elements 13, 21, 25, 22, 14 and 1 through the secondary winding every half cycle as in the positive case.
It is discharged through 9, 23, 26, 24 and 20 and falls to the peak value of the secondary voltage. As described above, even in the case of the negative voltage, the waveform following the envelope of the peak voltage of the secondary voltage, that is, the reference voltage E2
Can be generated.
The output voltage E5 is an extremely low frequency voltage having a waveform smoother than the smoothing circuit and the series resistor 28 and the capacitance of the device under test.

[0014]

As described above, according to the present invention, the device of the present invention is smaller in size than a conventional ultra-low frequency high voltage power supply which uses a polarity switcher and a discharge resistor in a rectifier circuit in a slidac system. The performance efficiency is increased and the service life is prolonged. In addition, by using a full-wave doubling voltage rectifier circuit for the rectification method, saturation of the iron core of the high-voltage transformer due to DC excitation and a sudden increase in the exciting current based on the saturation can be avoided, preventing overheating of the primary winding, miniaturization,
And the effect of reducing the input power capacity.

[Brief description of the drawings]

FIG. 1 is a basic circuit diagram of an ultra-low frequency high voltage power supply of the present invention.

FIG. 2 is an operation waveform diagram of each part of the basic circuit diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Commercial frequency power supply 2 AC switching regulator 3 High voltage transformer 4 Synchronous circuit 5, 6, 8, 9 AND circuit 7, 10 OR circuit 11 Reference power supply 12 Synchronous circuit 13 14, 15, 16, 17, 18, 19, 20 Rectification Element 21 22, 23, 24 Protective resistor 25, 26 High voltage semiconductor switch 27, 28 Smoothing capacitor 28 Series resistor E1 Commercial frequency power supply voltage E2 Reference voltage E3, E4 Smoothing capacitor 27, 28 Charging voltage E5 Output voltage P1, P2 , P3, P4 Synchronization signal 1P, 2P, 3P, 4P AND signal G1, G2 Gate signal

Claims (1)

[Claims] 1. A commercial frequency voltage is modulated by an ultra-low frequency reference power source sufficiently lower than the commercial frequency, the modulated voltage is applied to the primary side of a high voltage transformer, and the high voltage sides of the secondary windings have opposite polarities. Two pairs of rectifiers connected in series are connected in parallel,
Two sets of rectifier circuits are provided with their respective intermediate points connected by a high-voltage semiconductor switch. One end of each rectifier circuit is connected to one end of a secondary winding, and a full-wave double voltage rectifier circuit having the other end as an output. The gate signals of the two sets of high-voltage semiconductor switches are ANDed with the synchronization signals of the commercial frequency and the ultra-low frequency, respectively.
A signal through a circuit and an OR circuit, which is alternately transmitted to each gate terminal every time the polarity of the commercial frequency power supply is inverted according to an increase or decrease of the reference voltage, and a full-wave double voltage rectifier circuit is provided by a conducting operation of the high-voltage semiconductor switch; And a power supply for generating an ultra-low frequency high voltage corresponding to a reference voltage waveform at its output terminal through a smoothing circuit.