JPH1172533A - Power source apparatus for withstand voltage test - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the tuning time and facilitate the tuning work by carrying out a withstand voltage test by applying a voltage of a predetermined frequency to a circuit to be tested outside a case from an inverter while suppressing noises generated from the inverter. SOLUTION: A d.c. power feed part 4 converts a commercial a.c. source voltage Va into d.c. and outputs it. An inverter 5 converts the output of the d.c. power feed part 4 into an a.c. of a predetermined frequency and outputs it. A low-pass filter 6 shuts a high frequency band of an output of the inverter and cuts noises and a carrier frequency. A shielded transformer Ta is connected to an output of the low-pass filter via a first common mode choke 7a of a predetermined count, cuts noises of the output, transforms a voltage of the output and outputs. A case A stores the d.c. power feed part 4, etc., and is insulated from the ground. A optical cable 9 is used for a signal system connecting a control part 8 and the inverter 5 to prevent invasion of external noises. In the constitution, inverter noises are suppressed limitlessly and attenuated by 100 dB or more in comparison with the prior art.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for withstand voltage test of power equipment such as a transformer and a power cable.

[0002]

2. Description of the Related Art A withstand voltage test of a power device is to check whether or not a device performance withstands a rated voltage for a long time when a high voltage higher than a rated voltage is applied for a short time. Between terminals of winding equipment such as transformers (between both ends of winding)
There is an induction test performed in

In the above-described induction test, when a high voltage exceeding the rated voltage is applied between terminals of a transformer or the like at a rated frequency (50 or 60 Hz), the iron core is saturated, and a predetermined voltage cannot be applied. Therefore, rated frequency of 500Hz or 1kHz
After converting to a high frequency such as, for example, a high voltage is applied to the device for about one minute in 15 seconds or longer, and an example of an induction test power supply that converts to a high frequency and supplies a high voltage is referred to FIG. The test equipment (circuit under test) is shown below.

In FIG. 2, (1) is a high-frequency motor generator (Motor Genera) in which a generator (G) is connected to a motor (M).
ter), the motor (M) is connected to the commercial power supply (Va) through the circuit breaker (S) and driven, and the generator (G) is driven by the motor (M). The signal is converted into a desired high frequency and applied to the test reactor (La). At this time, when a high voltage is applied directly to the reactor (La) from the power supply device (1), the voltage includes a large amount of reactive power as well as active power, so that active and reactive power equivalent to the reactor under test is provided. Therefore, a high-frequency motor generator having a large capacity including the components is required.

[0005] Therefore, for example, 50
A compensation capacitor (Ca) that resonates at 0 Hz is connected in series to form a series resonance circuit, and the output frequency of the power supply (1) is set to a series resonance frequency determined by the inductance of the reactor (La) and the capacitance of the capacitor (Ca). Tune and resonate. Then, a predetermined high voltage larger than the power supply voltage (Va) and containing a large amount of reactive power is applied between the terminals of the reactor (La) due to resonance between the reactor (La) and the capacitor (Ca). Therefore, the power supply device (1) only needs to supply active power, and a large-sized high-frequency motor generator equivalent to a reactor under test is not required as the power supply device (1). In addition to the series resonance method, a parallel resonance method and the like are also known.

The above-described induction test using a high-frequency motor generator detects insulation breakdown (short circuit between terminals).
In addition, partial insulation deterioration that does not lead to insulation breakdown, for example, as shown in FIG. 3A, leakage current (Ia) between adjacent windings of the winding device (2) or leakage between case windings There is a corona test that detects the current (Ib). In the above corona test, if corona discharge occurs due to partial deterioration,
For example, since a high-frequency corona noise (Vn) having a shape unique to the sine wave voltage waveform (Vo) shown in FIG. 3B is generated, a corona discharge is detected from the noise shape to determine partial insulation deterioration, and It is to detect.

[0007]

According to the power supply device (1) using the high-frequency motor generator described above, it takes about several minutes to tune until reaching a predetermined frequency and voltage (current). When the test reactor (La) is thermally designed at the rated voltage, if the thermal stress is to be reduced, it is necessary to limit the high voltage application time during the induction test by the additional tuning time.

[0008] Therefore, if the application time of the high voltage is to be made as long as possible, it is necessary to design a device with a high tolerance for the induction test in consideration of the tuning time and the voltage, and to tune the high frequency motor generator. The required work requires skill and cannot be easily performed.Furthermore, for maintenance, the high-frequency motor generator is periodically dismantled to verify insulation deterioration and lubrication of the drive parts, etc. Time, manpower and cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply for a withstand voltage test which shortens the tuning time and facilitates the tuning operation.

[0010]

According to the present invention, there is provided an inverter which receives a DC converted from a commercial AC power supply at a DC power supply unit, converts the DC into an AC having a predetermined frequency, and outputs the AC. The inverter output is connected in series to the inverter output. The low-pass filter, the first common mode choke, and the shielded transformer input side, and the DC power supply, the inverter, the low-pass filter, the first common mode choke, and the shielded transformer are housed and insulated from the ground. An insulating housing, an isolation transformer for a separate power supply housed in the housing, a second common mode choke provided on the output side of the shielded transformer outside the housing, and a signal transmission between the inside and the outside of the housing. An optical cable, and performing a withstand voltage test by applying a voltage of a desired frequency from the inverter to a circuit under test outside the housing while suppressing noise generated by the inverter.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power supply device for withstand voltage test according to the present invention will be described below with reference to FIGS. 1 (a) and 1 (b). The feature of the present invention is that, in place of a high-frequency motor generator as an induction test power supply device, high-voltage power is supplied to a circuit under test using an inverter that converts a DC converted from a commercial AC power into an AC of an arbitrary frequency and outputs the AC. That is. According to the inverter, a predetermined frequency and voltage (or current) are reached in a short time (2 seconds or less), and tuning work is also easy.

However, since the inverter is basically operated by a switch using a semiconductor, noise is easily generated, and its frequency is close to the corona noise. Therefore, it can be discriminated from the corona noise generated in the corona test during the induction test. Is difficult. In addition, since an inverter noise of 1000 to 10000 times the corona noise occurs, in a normal state,
Inverter cannot be used in place of high frequency motor generator.
Therefore, in the present invention, as described below, the inverter is provided to the induction test power supply by suppressing the inverter noise as much as possible.

That is, the power supply device (3) according to the present invention shown in FIG. 1 (a) includes means for suppressing inverter noise as much as possible.
(5) is an inverter, (6) is a low-pass filter, (7a)
(7b) is the first and second common mode chokes, (Ta)
Is a transformer with a shield, and (A) is an insulation case to ground.

The DC power supply (4) is a three-phase transformer (T
b), rectifier (D), and smoothing capacitor (Cb) (Cc)
And converts the commercial AC power supply voltage (Va) to DC and outputs it. The inverter (5) converts the output of the DC power supply (4) into an AC having a predetermined frequency and outputs the AC. The low-pass filter (6) is made up of a reactor (Lb) and a capacitor (Cd), and cuts off high frequency of the inverter output to cut noise and carrier frequency.

The input side of the shielded transformer (Ta) is connected to the output of the low-pass filter via a predetermined number of first common mode chokes (7a). The insulated housing (A) houses the DC power supply (4), the inverter (5), the low-pass filter (6), the shielded transformer (Ta), and the first common mode choke (7a) and insulates it from the ground. , A shielded transformer outside the housing (A) (T
a) a predetermined number of second common mode chokes (7
b) is connected. Also, an optical cable (9) is connected to a signal transmission system between the inside and outside of the housing for transmitting a control signal from the external control system to the device in the housing, for example, a signal system connecting the control unit (8) outside the housing (A) and the inverter (5). ) To prevent external noise from entering.

Although not shown, for example, an auxiliary power supply for driving a cooling fan, a ventilation fan, and the like in the housing (A), and a control power supply for driving a failure indicator, a wiring board, and the like in the housing (A). And other system power is supplied from the outside to the housing (A) while being insulated from the outside via an insulating transformer in the housing (A).

According to the above configuration, the inverter noise is suppressed as much as possible, and 100 dB ｛(1/100) as compared with the related art.
000)}, so that the inverter noise is suppressed to (1/10) or less of the corona noise. Therefore, it is possible to distinguish between corona noise and inverter noise, and the power supply device (3) can be used for corona testing.

In addition, since the capacity of a single inverter is limited, as shown in FIG.
The input side of the plurality of inverters (5) is connected to a DC power supply unit (4).
May be connected in parallel, and the output side may be connected in series multiplexing via a transformer (Ta). The first common mode chokes (7a) are provided on each input side of the transformer (Ta), respectively, and the second common mode chokes (7b) are provided.
Are provided in common on the output side of the transformer (7a)... And the capacitor (Ca) and the reactor (L) are connected via the transformer (Tc).
a).

In the above embodiment, the power supply for induction test has been described. However, the present invention is not limited to this, and can be applied to, for example, a cable in which a conductor is covered with an insulator. In this case, since a capacitor is equivalently formed between the conductor and the coated insulator, a resonance circuit is formed by connecting the compensating reactors in series, and a withstand voltage test and a corona test are also performed. Detects dielectric breakdown and partial deterioration between conductors and conductors.

[0020]

According to the present invention, since a low-noise inverter that suppresses noise as much as possible is used as a power supply for a withstand voltage test instead of a high-frequency motor generator, tuning until a predetermined frequency and voltage or current are reached is achieved. The test time can be shortened and the test can be performed without applying thermal stress to the circuit under test.The good operability of the inverter also simplifies the tuning work. The running cost is greatly reduced.

[Brief description of the drawings]

FIG. 1A is a circuit block diagram showing an embodiment of a power supply device for withstand voltage test according to the present invention. (B) is a circuit block diagram showing a large-capacity embodiment of the power supply device for withstand voltage test according to the present invention.

FIG. 2 is a circuit block diagram showing a conventional example of a withstand voltage test power supply device.

FIG. 3A is a circuit diagram showing leakage current due to partial insulation deterioration of a winding device. (B) is a voltage waveform diagram of a corona test.

[Explanation of symbols]

 Reference Signs List 3 power supply unit 4 DC power supply unit 5 inverter 6 low-pass filter 7a first common mode choke 7b second common mode choke Ta Transformer with shield A Insulated housing Va Commercial AC power supply

Claims (1)

[Claims] An inverter for receiving a DC converted from a commercial AC power supply at a DC power supply unit and converting the DC power to an AC having a predetermined frequency; a low-pass filter sequentially connected in series to the inverter output; An insulated housing that houses the common mode choke and the shielded transformer input side, houses the DC power supply unit, the inverter, the low-pass filter, the first common mode choke and the shielded transformer, and insulates the ground; An insulation transformer for a separate system power supply housed in a housing, a second common mode choke provided on the output side of the shielded transformer outside the housing, and an optical cable for transmitting a signal between the inside and the outside of the housing. A voltage of a desired frequency is applied from an inverter to a circuit to be tested outside a housing while performing a withstand voltage test while suppressing noise generated by the withstand voltage test.