CN110376442B

CN110376442B - Auxiliary measuring device for measuring insertion loss of power filter of shielding facility

Info

Publication number: CN110376442B
Application number: CN201910499486.0A
Authority: CN
Inventors: 柳光福
Original assignee: AERODEV ELECTROMAGNETIC TECH Inc
Current assignee: AERODEV ELECTROMAGNETIC TECH Inc
Priority date: 2019-06-11
Filing date: 2019-06-11
Publication date: 2021-06-11
Anticipated expiration: 2039-06-11
Also published as: CN110376442A

Abstract

The invention relates to an auxiliary measuring device for measuring the insertion loss of a power filter of a shielding facility, which is characterized by comprising a hollow copper cylinder I, wherein the lower end of the copper cylinder I is opened, the upper end of the copper cylinder I is closed by a copper plate, and after the auxiliary measuring device is installed in place, the lower end of the copper cylinder I is electrically connected with a metal shield of the filter; an RF connector is arranged on the copper plate; a copper nut cylinder is arranged in the first copper cylinder, the copper nut cylinder is connected with an inner conductor of the RF connector through a lead, and a bolt terminal of the input end or the output end of the filter extends into the first copper cylinder to be meshed with the copper nut cylinder, so that the RF connector is connected to the input end or the output end of the filter; and an insulator is arranged between the copper nut cylinder and the inner wall of the copper cylinder I. The invention enables the insertion loss to be measured as specified in the standard GB/T7343 and also enables the electromagnetic coupling that may exist between the input and the output of the filter to be controlled very efficiently.

Description

Auxiliary measuring device for measuring insertion loss of power filter of shielding facility

Technical Field

The invention relates to a method for measuring the insertion loss of a power filter of a shielding facility according to the standard GB/T7343, belonging to the technical field of measurement of the suppression characteristic of a passive EMC filter.

Background

The measurement of the insertion loss of the shielding facility power filter belongs to the category of a standard GB/T7343-2017/IEC/CISPR 17:2011 measurement method for the rejection characteristic of a passive EMC filter (hereinafter referred to as GB/T7343).

According to the standard GB/T7343, the filter under test is placed in a test box according to section 5.2.2.4 of the standard when testing the rejection characteristics of a passive EMC filter. The power filter of the shielding facility is huge in size, and the mass of the power filter is in the range of dozens of kilograms or even hundreds of kilograms. Firstly, it is expensive to manufacture test cases according to the specification 5.2.2.4 of the standard GB/T7343. For example, the external dimensions of a three-phase four-wire shielded room power filter are 1300 (long), 500 (wide) and 170 (high); according to the specification of B.1.3 (page 30) in the standard GB/T7343, a space of 50mm is reserved around and above the test box of the tested filter, so that the size of the test box for implementing the filter is larger; secondly, the weight of the three-phase four-wire shielding chamber power filter reaches 133kg, and the three-phase four-wire shielding chamber power filter is almost impossible to be put into a test box or moved out of the test box by manpower during measurement. Third, the test box is designed according to the examples of B.3 (standard page 30) and B.4 (standard page 31) recommended by the standard GB/T7343. The essence of the test box examples of b.3 and b.4 is to control the electromagnetic coupling between the input and output of the filter under test to a minimum level. Because the insertion loss characteristic of the screening plant power filter is greater than 100 dB. The authenticity of the insertion loss measurement is affected by any electromagnetic coupling between the input and output of the filter.

As shown in fig. 1, a schematic diagram of a three-phase four-wire power filter 100 installed in an EMC darkroom 70 for a shielded facility. In fig. 1, 60 is a control room; 40 is the power inlet of the filter, i.e. the input of the filter; and 50 is the through-wall outlet of the filter, i.e. the output of the filter. 11-11 ', 12-12', 13-13 'and 14-14' are respectively four branches of the filter, and are respectively connected with three phase lines and a neutral line of the power supply system. Whether developing or producing a screening facility power filter, the insertion loss of such filters is measured.

Figure 2 is an outline view of a power filter for a shielded installation of a certain type. In fig. 2, 99 is the metal shield of the filter; 97 is the junction box cover plate of the filter output; 96 is the terminal box cover plate of the filter input; 40 is the stuffing box of the cable into the filter input terminal box.

The

cover plates

96 and 97 of the junction box in fig. 2 are removed to form the external view of fig. 3. Originally, terminal block cover plate 97 and terminal block cover plate 96 in fig. 2 cover square holes at both ends of the filter, which are provided for facilitating the connection of cables to the bolt terminals of the branches 11-11 ', 12-12', 13-13 'and 14-14' of the filter. However, only the bolts of the

branch terminals

11, 12 and 13 can be seen in fig. 3. After the cable is connected, the terminal

block cover plates

96 and 97 at the two ends are mounted in situ to ensure that the electromagnetic coupling between the input and output ports of the filter is controlled to an extremely low level.

To further understand the bolt terminals of the filter, the upper part of fig. 3 is cut away and the filter is turned 180 degrees, resulting in fig. 4. This makes it possible to see the 4 branches 11-11 ', 12-12', 13-13 'and 14-14' of the filter and the distribution of all 8 bolt terminals.

The structure of the bolt terminal is shown in fig. 5. In fig. 5, 21 is a bolt, which is a part to which the cables at the input or output ends of the branches of the power filter of the shielding facility are connected, and the other end of the bolt is connected with the filter circuit; 22 is a fastener nut; 23 is a spring washer; 24 is a flat washer; and 25 is an insulator. The bolt terminal is fixed to the metal shield 99 of the filter by the insulator 25, and the bolt 21 of the filter is electrically insulated from the metal shield 99 of the filter.

Fig. 6A and 6B are typical designs of the "fig. b.3 punch-through element test box" on page 30 of standard GB/T7343. The square holes 98 in fig. 6A and 6B function similarly to the square holes pressed by the terminal

block cover plates

97, 96 in fig. 2, and are provided for the convenience of filter connection. The bolt 21 in fig. 5 corresponds to the member 121 in fig. 6A and 6B. The insulator 25 in fig. 5 corresponds to the member 125 in fig. 6A and 6B. If the rf connector 101 of fig. 6 can be mounted on the metal shield at both ends of the power filter of the shield facility shown in fig. 2 and connected to a measuring instrument such as a vector network analyzer, measurement of the insertion loss of the filter can also be performed. However, this is not allowed on filter products, since the provision of the rf connector destroys the electromagnetic isolation between the input and output of the filter and also the insertion loss of the filter.

Disclosure of Invention

The purpose of the invention is: an auxiliary device for the measurement of the insertion loss of a power filter of a shielded facility is provided, which is economical and convenient, according to the standard GB/T7343.

In order to achieve the above object, the technical solution of the present invention is to provide an auxiliary measuring device for measuring insertion loss of a power filter of a shielding facility, which is characterized by comprising a hollow copper cylinder i, wherein the lower end of the copper cylinder i is open, and the upper end of the copper cylinder i is closed by a copper plate; an RF connector is arranged on the copper plate; a copper nut cylinder is arranged in the first copper cylinder, the copper nut cylinder is connected with an inner conductor of the RF connector through a lead, and after the auxiliary measuring device is installed in place, a bolt terminal of the input end or the output end of the filter extends into the first copper cylinder to be meshed with the copper nut cylinder, so that the RF connector is connected to the input end or the output end of the filter; and an insulator is arranged between the copper nut cylinder and the inner wall of the copper cylinder I.

Preferably, the copper plate and the first copper cylinder are integrally formed, or the copper plate is fixed at the upper end of the first copper cylinder through a connecting piece, or the copper plate and the first copper cylinder are fixedly welded.

Preferably, the RF connector is a male connector or a female connector.

Preferably, N layers of metal wire gaskets are arranged between the lower end of the copper cylinder and the metal shield of the filter, and N is more than or equal to 1; or M layers of metal wire gaskets are arranged between the lower end of the copper cylinder and the metal shield of the filter, M is more than or equal to 2, and a copper cylinder II is arranged between the metal wire gasket on the metal shield and the metal wire gasket of the copper cylinder.

Preferably, the insulator is fixedly connected with the copper plate through a connecting piece; the insulator is fixedly connected with the side face of the first copper cylinder through a connecting piece.

Preferably, a baffle is arranged in the first copper cylinder, the copper nut cylinder and the insulator are located between the baffle and the copper plate, the bolt terminal at the input end or the output end of the filter penetrates through the baffle and then is meshed with the copper nut cylinder, and the baffle is used for preventing the copper nut cylinder from displacing in the meshing process with the bolt terminal.

Preferably, the baffle is locked in position by a plurality of connectors circumferentially threaded through the copper cylinder.

Aiming at the characteristics of large and heavy power filters of the power supply of the shielding facilities, the invention provides a low-cost auxiliary measuring device which can conveniently and accurately measure the insertion loss of the power supply of the shielding facilities according to the standard GB/T7343. The invention relates to an auxiliary test device for measuring the insertion loss of a power filter of a shielding facility according to the standard GB/T7343, which can not only measure the insertion loss according to the specification of the standard GB/T7343, but also effectively control the possible electromagnetic isolation between the input and the output of the filter.

Drawings

FIG. 1 is a shielded utility power filter installed in an EMC darkroom;

FIG. 2 is an external view of a power filter of a shield facility;

FIG. 3 shows two square holes with the input and output covers of the power filter of the shielding facility removed;

FIG. 4 is a cross-sectional view of eight bolt terminals and input stuffing boxes, output wall penetrators of a power filter of a shielding facility, which can be seen clearly;

FIG. 5 is a bolt end view of a shield utility power filter;

FIGS. 6A and 6B are typical designs of the feed-through device test chamber of FIG. B.3 of Standard GB/T7343;

FIGS. 7A and 7B are cross-sectional views of an insertion loss measurement aid of embodiment 1 of standard GB/T7343;

FIGS. 8A and 8B are views of the hexagonal copper nut cylinder of FIGS. 7A and 7B;

FIGS. 9A and 9B are views of the insulator of FIGS. 7A and 7B;

FIG. 10 is a graph of asymmetric insertion loss of a power filter of a screening facility measured using a standard GB/T7343 insertion loss measurement aid;

FIG. 11 shows the symmetric insertion loss of a power filter of a screening facility measured using a standard GB/T7343 insertion loss measurement aid;

fig. 12A and 12B are sectional views of an insertion loss measurement support device according to example 2 of the standard GB/T7343.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

Example 1

As shown in fig. 7A and 7B, an auxiliary device for measuring the insertion loss of the power filter of the shielded facility according to the standard GB/T7343 in this embodiment is an RF connector of 50 ohm SMA, and is specifically designed for the small-sized square holes at the two ends of the filter in fig. 3. When the insertion loss of the power filter of the shielding facility is measured according to the standard GB/T7343, the auxiliary device in fig. 7A and 7B is required to be electrically connected with 8 bolt terminals in fig. 4. If the auxiliary device in fig. 7A and 7B is a female SMA connector 201, it is also connected to a cable (not shown) with a male SMA head, so as to electrically connect the tested filter bolt terminal to the measuring instrument. The size of the SMA male cable and the size of the cable that allows deformation must be taken into account when designing.

A 50 ohm SMA connector 201 is mounted to a copper plate 203 by screws 202. The copper plate 203 has an outer diameter of 42 mm. The copper plate 203 is fixed to a copper cylinder 205 by screws 206. The copper cylinder 205 has an outer diameter of 42mm and an inner diameter of 34 mm. The lower end of the copper cylinder 205 of the standard GB/T7343 insertion loss measurement aid, which is mounted in place, is to be able to make good electrical connection with the metal shield 99 of the filter of fig. 5.

The inner conductor of the SMA connector 201 makes an electrical connection with the hex copper nut cylinder 208 via a solder wire 216. The hexagonal copper nut cylinder 208 is shown in fig. 8A and 8B, and its cross-section corresponds to the external dimensions of the nut of international M6. The hexagonal copper nut cylinder 208 is 18mm long, the lower end of the side view is about 7mm, the hexagonal copper nut cylinder is processed into a national standard nut, and the upper end part of the hexagonal copper nut cylinder is processed into a hole with the diameter of 9 mm.

The hexagonal copper nut post 208 in fig. 8A and 8B is disposed within the insulator 207 shown in fig. 7A and 7B. The insulator 207 is made of an ABS material by a 3D printing process, and the structure of the insulator 207 is shown in fig. 9A and 9B. The 3-2.4 mm holes in fig. 9B were machined as M3 screw holes because 3D printing did not allow the screw holes to be molded. The insulator 207 shown in fig. 7A and 7B is fixed to the copper plate 203 by 3 screws 212 shown in fig. 7B. The 4 circular holes intersecting the hexagon in fig. 9B are fabrication holes.

In order to prevent the hexagonal copper nut cylinder 208 of fig. 7A and 7B from being displaced during engagement with the bolt terminal of the filter shown in fig. 5, a stopper 209 is provided. The baffle 209 is a circular ring made of insulating material with a central aperture of 8mm and a thickness of 3mm, and is locked by 3M 3 screws 210 on the copper cylinder 205 side.

In fig. 7A and 7B, the copper plate 203 and the copper post 205 may be connected by welding or may be integrally formed.

On the one hand, the lower end of the copper pillar 205 can be electrically connected to the metal shield 99 of the filter of fig. 5; on the other hand, the inner conductor of the SMA connector 201 is connected to the hexagonal copper nut cylinder 208 via the wire 216, and is engaged with the bolt 21 in fig. 5, so that the SMA connector 201 is connected to the input or output terminal of the filter. The standard GB/T7343 insertion loss measurement aid shown in fig. 7A and 7B implements all the elements of the typical design of the test box of fig. 6A and 6B that control the electromagnetic coupling that may exist between the filter input and output.

The asymmetric insertion loss measurement of the filter branch 11-11 'can be performed as shown in figure 7 on page 11 of the standard GB/T7343 by mounting one auxiliary device at terminal 11 in figure 4 and the other auxiliary device at terminal 11' in figure 4.

By simultaneously fitting 4 auxiliary devices shown in fig. 7A and 7B onto the

bolt terminals

11, 11 ', 12 and 12' in fig. 4, the symmetrical insertion loss between the filters 11-11 'and 12-12' can be measured as shown in fig. 6 on page 10 of GB/T7343.

By analogy, 4 asymmetric insertion loss curves and 6 symmetric insertion loss curves of the 3-phase and 4-phase shielded facility power filter in fig. 1 can be measured.

To accommodate engineering errors, for example, the perpendicularity tolerance of the bolt 21 with respect to the metal shield 99 of the filter in fig. 5; in practical applications, such as tolerance generated by the hexagonal copper nut cylinder 208 embedded in the insulator 207 in fig. 7A and 7B, a wire washer (commercially available) with a thickness of 2mm, an outer diameter of 45mm, and an inner diameter of 34mm is inserted between the lower end of the copper cylinder 205 in fig. 7 and the metal shield 99 of the filter in fig. 5, so that the telescopic performance is excellent. With the buffering of the filter, the perfect electric connection between the lower end of the copper cylinder 205 in fig. 7A and 7B and the metal shield 99 of the filter in fig. 5 can be realized, so that the electromagnetic coupling between the auxiliary device port for measuring the insertion loss of the standard GB/T7343 shown in fig. 7A and 7B and the ports of other filters can be controlled to a level lower than 100dB, and the accurate, efficient and reliable measurement of the insertion loss of the power filter of the shielding facility measured according to the standard GB/T7343 can be ensured. Fig. 10 is an asymmetric insertion loss curve of the SNF710-4X32 shielded utility power filter measured by the auxiliary device, and fig. 11 is a symmetric insertion loss curve of the SNF710-4X32 shielded utility power filter measured by the auxiliary device.

The auxiliary device shown in fig. 7A and 7B is suitable for use in fig. 5 where the distance from the M6 bolt 21 to the filter shield is 23.5-35mm (including 2mm wire washers), according to the dimensions described above.

Example 2

For high current shielded utility power filters, the bolt terminals in fig. 5 may be M8, M10, or M12. The connected cable is thick and hard, and the installation of the cable is difficult. The two square holes at the two ends of the filter, which are designed for the installation of cables in fig. 3, are enlarged in size, and for this purpose another auxiliary device for measuring the insertion loss of the power filter of the screening installation according to the standard GB/T7343 is designed specifically in fig. 12A and 12B.

In fig. 12A and 12B, 201' is a 50-ohm N-type RF connector, and since the area of the copper plate 203 is limited, the fixing position of the insulator 207 is changed and fixed by a screw 212 located on the side surface of the copper post 205.

The hexagonal copper nut cylinder 208 and the insulator 207 in fig. 12A and 12B are designed according to the external dimension of M12, and are designed into hexagonal copper nut cylinders of M8 and M10 under the principle that the external dimension of M12 in the hexagonal copper nut cylinder 208 is not changed, and the external dimensions are consistent, and only threaded holes are respectively M8, M10 and M12. With such a design, it is only necessary to manufacture four sets of auxiliary devices shown in fig. 12A and 12B, and replace the hexagonal copper nut 208 with different threads as necessary, so as to complete the measurement of the symmetric and asymmetric insertion loss of the power filter of the shielding facility with the bolts M8, M10 and M12 in fig. 5.

The remaining definitions in fig. 12A and 12B are the same as in fig. 7A and 7B.

When the height of the copper cylinder 205 in fig. 12A and 12B is 55mm, the height of the insulator 207 is 40mm, the thickness of the baffle 209 is 3mm, and a 2mm wire washer is included, the auxiliary device in fig. 12A and 12B is suitable for the case where the distance from the bolt 21 of M8, M10 and M12 to the filter shield is 23.5-38.5mm in fig. 5.

In applications where the distance from the bolt 21 to the filter shield in fig. 5 may exceed the limit dimensions that can be accommodated in fig. 7A and 7B and fig. 12A and 12B, the following two options may be used: one) increasing the number of wire washers between the copper cylinder and the filter metal shield; secondly) a section of copper column with proper size is inserted between the metal wire gasket on the metal shield 99 of the filter of fig. 5 and the metal wire gasket connected with the copper column 205, so that the length of the input or output bolt of the power filter of the shielding facility can be lengthened.

Claims

1. An auxiliary measuring device for measuring the insertion loss of a power filter of a shielding facility is characterized by comprising a first hollow copper cylinder, wherein the lower end of the first copper cylinder is opened, the upper end of the first copper cylinder is closed by a copper plate, and after the auxiliary measuring device is installed in place, the lower end of the first copper cylinder is electrically connected with a metal shield of the filter; an RF connector is arranged on the copper plate; a copper nut cylinder is arranged in the first copper cylinder, the copper nut cylinder is connected with an inner conductor of the RF connector through a lead, and after the auxiliary measuring device is installed in place, a bolt terminal of the input end or the output end of the filter extends into the first copper cylinder to be meshed with the copper nut cylinder, so that the RF connector is connected to the input end or the output end of the filter; and an insulator is arranged between the copper nut cylinder and the inner wall of the copper cylinder I.

2. An auxiliary measuring device for measuring the insertion loss of a power filter of a shielding facility according to claim 1, wherein said copper plate is formed integrally with said copper cylinder, or said copper plate is fixed to the upper end of said copper cylinder by a connecting member, or said copper plate is fixed to said copper cylinder by welding.

3. An auxiliary measuring device for measuring the insertion loss of a power filter of a shielded facility according to claim 1, wherein said RF connector is either a male connector or a female connector.

4. An auxiliary measuring device for measuring the insertion loss of a power filter of a shielding facility as claimed in claim 1, wherein a N-layer metal wire gasket is provided between the lower end of the first copper cylinder and the metal shield of the filter, wherein N is more than or equal to 1; or M layers of metal wire gaskets are arranged between the lower end of the first copper cylinder and the metal shield of the filter, M is more than or equal to 2, and a second copper cylinder is arranged between the metal wire gasket on the metal shield and the metal wire gasket of the first copper cylinder.

5. An auxiliary measuring device for measuring the insertion loss of a power filter of a shielded facility according to claim 1, wherein said insulator is fixedly connected to said copper plate by a connecting member; the insulator is fixedly connected with the side face of the first copper cylinder through a connecting piece.

6. An auxiliary measuring device for measuring the insertion loss of a power filter of a shielding facility as claimed in claim 1, wherein a baffle is provided in the first copper cylinder, the copper nut cylinder and the insulator are located between the baffle and the copper plate, the bolt terminal at the input end or the output end of the filter passes through the baffle and then engages with the copper nut cylinder, and the baffle is used for preventing the copper nut cylinder from being displaced during the engagement with the bolt terminal.

7. An auxiliary measuring device for measuring the insertion loss of a power filter of a shielded facility according to claim 6, wherein said baffle is locked by a plurality of connectors circumferentially disposed on said first copper post.