CN115792397A - Power grid EMI filter insertion loss test method - Google Patents
Power grid EMI filter insertion loss test method Download PDFInfo
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- CN115792397A CN115792397A CN202211300946.0A CN202211300946A CN115792397A CN 115792397 A CN115792397 A CN 115792397A CN 202211300946 A CN202211300946 A CN 202211300946A CN 115792397 A CN115792397 A CN 115792397A
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Abstract
The invention provides a method for testing the insertion loss of an EMI filter of a power grid, belonging to the technical field of electronic testing. The test method mainly comprises three steps of firstly building a test bench according to an actual operation state, then testing voltage and current conduction emission spectrum curves before and after switching of the tested filter, and finally obtaining insertion loss through data conversion before and after switching. The method has the characteristics of good modeling property, high accuracy, good repeatability, strong reproducibility and the like, can be used as a supplement of a standard insertion loss test method, and is used for batch test and performance acceptance of the EMI filter of the naval power grid.
Description
Technical Field
The invention relates to a method for testing the insertion loss of an EMI filter of a power grid, belonging to the technical field of electronic testing.
Background
The electromagnetic interference is divided into radiation interference and conduction interference according to propagation types, and due to the limitation of the power grid capacity and the spatial arrangement of the ship platform, the probability of the occurrence of the latter interference is more obvious in the ship platform, so that the adoption of anti-interference measures to control the conduction interference is a main problem to be solved in the electromagnetic compatibility overall design of the ship platform.
Conducted disturbances occurring via the power supply line are a typical case of conducted disturbances, which on the one hand come from the grid start (generator) and on the other hand from various consumers. Various electromagnetic compatibility assessment standards provide assessment requirements on conducted emission for the two types of equipment, for example, the equipment needs to meet the requirements of CE101 and CE102 in GJB151B, the generator needs to meet the requirements of CE01 and CE03 in HJB34A, and the power grid of a ship platform needs to meet the requirements of power grid low-frequency conducted emission and power grid radio frequency conducted emission limits in HJB 34A.
Under the mode that the existing ship generally adopts three-level electromagnetic compatibility control, namely 'overall, system and equipment', all levels need to take measures to control power lines to conduct and emit. In order to control the electromagnetic environment level of the platform power grid, the most common design measure currently used by the platform overall design unit is to arrange a power grid EMI filter on the power grid to filter conducted emissions from the power grid and devices, so as to achieve the purpose of isolating conducted interference. The most important index of the power grid EMI filter is insertion loss which represents the filtering capability of the filter, the insertion loss of the filter is mostly tested through a network analyzer when the filter is subjected to factory acceptance, the method is characterized in that data (both the impedance of a source end and the impedance of a load end are 50 omega) obtained in a 50 omega system is an ideal condition, the impedance difference with a power grid and the load impedance of an actual platform is large, large errors are caused when a general unit conducts interference simulation by using the data, and related electromagnetic compatibility evaluation work is difficult to accurately carry out. How to simulate an actual platform, a better solution is not found for accurately testing the insertion loss of the power grid EMI filter in the actual working state.
Disclosure of Invention
In view of the above, the application provides a power grid EMI filter insertion loss test method, which aims to build a power grid system and a load simulating a ship platform, feed back an interference signal to a power grid by using the electromagnetic characteristics of the load, and obtain insertion loss approaching to a real operation state by using the ratio of electromagnetic emission data before and after filtering.
The technical scheme for realizing the invention is as follows:
a power grid EMI filter insertion loss test method is characterized by comprising the following specific processes:
step one, building a power grid EMI filter insertion loss test system;
the system comprises: the system comprises an isolation transformer, a collection device, a first power supply switching device, a second power supply switching device, a variable frequency power supply and a load;
the input of the isolation transformer is connected with the power supply distribution cabinet, and the output of the isolation transformer is connected with the input of the first power supply switching device; the output of the first power supply switching device is divided into two paths, one path is connected with the second power supply switching device, and the other path is connected with the input of the tested power grid EMI filter; the input of the second power supply switching device is divided into two paths, one path is connected with the output of the first power supply switching device, and the other path is directly connected with the output of the tested power grid EMI filter; the input of the variable frequency power supply is connected with the output of the second power supply switching device, and the output of the variable frequency power supply is connected with the load; the acquisition device is connected between the isolation transformer for the warship and the first power supply switching device;
step two, switching two power supply switching devices, respectively testing the voltage and current conducted emission spectrum curves of the system before and after the switching of the tested power grid EMI filter, and adjusting a variable frequency power supply and a load during testing to enable the current of the circuit to reach a rated state;
and step three, reading the switching frequency of the variable frequency power supply and the voltage value of the harmonic wave of the variable frequency power supply in the frequency spectrum curve, and calculating the voltage and current insertion loss of the power grid EMI filter.
Further, the specific process of the second step is as follows:
a) The two power supply switching devices are switched to ensure that one path which is not accessed by the EMI filter of the tested power grid is connected; adjusting a variable frequency power supply and a load according to the rated current of the EMI filter of the tested power grid to enable the current of a circuit to reach a rated state;
b) Testing a voltage and current conduction emission spectrum curve in the state that the EMI filter of the power supply to be tested is not connected;
c) The two power supply switching devices are switched to ensure that one path connected with the tested power grid EMI filter is connected;
d) And repeating the step b), and testing the current conducted emission spectrum curve and the voltage conducted emission spectrum curve in the state that the tested power grid EMI filter is connected.
Furthermore, the acquisition device comprises two frequency spectrometers, the first frequency spectrometer is connected with the L line output by the marine isolation transformer through a current joint, and the second frequency spectrometer is connected with the L line and the N line output by the marine isolation transformer through a voltage joint.
Further, when the voltage and current conducted emission spectrum curve in the state of no tested power grid EMI filter access is tested, a first frequency spectrograph and a current probe are used for testing and obtaining a current conducted emission spectrum curve I in the state of no filtering CE1 (ii) a Obtaining a voltage conduction emission spectrum curve U in a non-filtering state by using a second frequency spectrograph and a voltage probe for testing CE1 (ii) a When testing voltage and current conducted emission in the state of being connected with the tested power grid EMI filter, a current conducted emission spectrum curve I in the state of no filtering is obtained by using a first frequency spectrograph and a current probe for testing CE2 (ii) a Obtaining a voltage conduction emission spectrum curve U in a non-filtering state by using a second frequency spectrograph and a voltage probe for testing CE2 ；
At U CE1 And U CE2 The frequency spectrum curve of the variable frequency power supply is read, and the voltage values of the switching frequency and the harmonic wave of the variable frequency power supply are respectively U CE1N And U CE2N N denotes the harmonic order, i.e. N =1 denotes the fundamental wave of the switching frequency, N =3 denotes the 3 rd harmonic of the switching frequency;
when calculating the voltage insertion loss, the voltage insertion loss U is calculated according to the following formula dB ：
U dB ＝U CE1N -U CE2N ；
When calculating the current insertion loss, the current insertion loss I is calculated according to the following formula dB ：
I dB ＝I CE1N -I CE2N 。
Further, the load formed by the variable frequency power supply and the load is not less than the equivalent capacity of the tested power grid EMI filter.
Further, the switching frequency of the variable frequency power supply is less than 10kHz.
Has the advantages that:
(1) The testing system is set up, interference signals are fed back to a power grid by using the electromagnetic characteristics of the load, the insertion loss approaching to the real running state is obtained through the ratio of electromagnetic emission data before and after filtering, and the accuracy of a testing result is higher than 90%.
(2) The test system built by the method is low in complexity, controllable in cost and good in economy and reproducibility.
(3) In the test system, the output of the first power supply switching device is divided into two paths, one path is connected with the second power supply switching device, the other path is connected with the input of the tested power grid EMI filter, the test system can be used for batch test and performance acceptance of the power grid EMI filter, and the test repeatability is good.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is an embodiment of an insertion loss testing system for a grid EMI filter;
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The test system of this embodiment is built under the environment based on naval vessel system, and used power distribution cabinet adopts the AC380V switch board, and isolation transformer selects for use naval vessel isolation transformer.
A method for testing insertion loss of a grid EMI filter, as shown in fig. 1, includes: the device comprises a marine isolation transformer 1, a first power supply switching device 2.1, a second power supply switching device 2.2, a variable frequency power supply 3, a pure resistance load 4, a first frequency spectrograph 6.1, a current connector 6.2, a second frequency spectrograph 7.1 and a voltage connector 7.2;
the marine isolation transformer 1 is selected according to the design of a ship, the marine isolation transformer 1 is connected with a three-phase U, V, W of an AC380V power distribution cabinet, a voltage probe 7.2 is connected with an L line and an N line of an AC220V power supply output by the marine isolation transformer 1 in a voltage reduction mode, and a current probe 6.2 is clamped on the L line of the AC220V power supply output by the marine isolation transformer 1 in the voltage reduction mode;
the L line and the N line of an AC220V power supply output by the ship isolation transformer 1 in a voltage reduction mode are connected with a first power supply switching device 2.1, 4 output lines are led out from the first power supply switching device 2.1 and comprise 2L lines and 2N lines, and the first power supply switching device 2.1 ensures that only one group of L lines and the N lines are in a connection state through switching;
a group of L and N lines output by the power supply switching device 2.1 are connected with the input of the tested power grid EMI filter 5, and the output of the tested power grid EMI filter 5 is connected with the input of the second power supply switching device 2.2; the other group of L and N lines output by the first power supply switching device 2.1 is connected with the input of the second power supply switching device 2.2, the second power supply switching device 2.2 ensures that only one group of L and N lines are in a connected state through switching, and only 1 path of L and N lines are led out to be used as output;
the output of the second power supply switching device 2.2 is used as the power supply of the adjustable variable frequency power supply 3 and is connected with the input of the adjustable variable frequency power supply 3, and the adjustable pure resistance load 4 is used as the load of the adjustable variable frequency power supply 3 and is connected with the load; the load formed by the adjustable variable frequency power supply 3 and the adjustable pure resistance load 4 is not less than the equivalent capacity of the tested power grid EMI filter, if the rated current of the filter is 10A, the variable frequency power supply and the resistance load can be adjusted to reach 2200W (220V multiplied by 10A) of power load; the variable frequency power supply has a typical switching characteristic, the switching frequency is less than 10kHz, and obvious switching frequency and harmonic characteristic signals thereof can be observed in a frequency spectrum curve obtained by a CE102 method in GJB 151B;
after the system is built, the online warship AC220V power grid EMI filter insertion loss test is developed according to the following steps and methods:
1. and testing voltage and current conduction emission before and after the tested filter is switched.
a) The first power supply switching device 2.1 and the second power supply switching device 2.2 are switched to ensure that the group of L and N lines which are not accessed by the tested power grid EMI filter 5 are in a connection state; according to the rated current of the tested power grid EMI filter 5, the adjustable variable frequency power supply 3 and the adjustable pure resistance load 4 are adjusted to enable the current in the circuit to reach the rated state;
b) The voltage and current conducted emissions were tested without the tested grid EMI filter 5 being switched in. According to the method of CE01 in HJB34A-2007, a current conduction emission spectrum curve I in a non-filtering state is obtained by testing with a first spectrometer 6.1 and a current probe 6.2 CE1 (ii) a According to the method for conducting interference in the power grid in HJB237-2001, a voltage conduction emission spectrum curve U in a non-filtering state is obtained by using a second frequency spectrograph 7.1 and a voltage probe 7.2 for testing CE1 ；
c) The first power supply switching device 2.1 and the second power supply switching device 2.2 are switched to ensure that the group of L and N lines accessed by the tested power grid EMI filter 5 are in a connection state;
d) Obtaining a current conduction emission spectrum curve I under the state that the power grid EMI filter is connected according to the method b) CE2 Sum voltage conducted emission spectrum curve U CE2 ；
2. Converting the ratio to obtain insertion loss;
a) At U CE1 And U CE2 The frequency spectrum curve of the variable frequency power supply is read, and the voltage values of the switching frequency and the harmonic wave of the variable frequency power supply are respectively U CE1N And U CE2N N denotes the harmonic order, i.e. N =1 denotes the fundamental wave of the switching frequency and N =3 denotes the 3 rd harmonic of the switching frequency.
b) Calculating the voltage insertion loss U according to equation (1) dB ；
U dB ＝U CE1N -U CE2N (1)
c) Calculating the current insertion loss I according to the formula (2) with reference to the step a) dB ；
I dB ＝I CE1N -I CE2N (2)
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. A power grid EMI filter insertion loss test method is characterized by comprising the following specific processes:
step one, building a power grid EMI filter insertion loss test system;
the system comprises: the system comprises an isolation transformer, a collection device, a first power supply switching device, a second power supply switching device, a variable frequency power supply and a load;
the input of the isolation transformer is connected with the power supply distribution cabinet, and the output of the isolation transformer is connected with the input of the first power supply switching device; the output of the first power supply switching device is divided into two paths, one path is connected with the second power supply switching device, and the other path is connected with the input of the tested power grid EMI filter; the input of the second power supply switching device is divided into two paths, one path is connected with the output of the first power supply switching device, and the other path is directly connected with the output of the tested power grid EMI filter; the input of the variable frequency power supply is connected with the output of the second power supply switching device, and the output of the variable frequency power supply is connected with the load; the acquisition device is connected between the isolation transformer for the warship and the first power supply switching device;
step two, switching two power supply switching devices, respectively testing the voltage and current conducted emission spectrum curves of the system before and after the switching of the tested power grid EMI filter, and adjusting a variable frequency power supply and a load during testing to enable the current of the circuit to reach a rated state;
and step three, reading the switching frequency of the variable frequency power supply and the voltage value of the harmonic wave of the variable frequency power supply in the frequency spectrum curve, and calculating the voltage and current insertion loss of the power grid EMI filter.
2. The method of claim 1, wherein: the specific process of the second step is as follows:
a) The two power supply switching devices are switched to ensure that one path which is not accessed by the EMI filter of the tested power grid is connected; adjusting a variable frequency power supply and a load according to the rated current of the EMI filter of the tested power grid to enable the current of a circuit to reach a rated state;
b) Testing a voltage and current conducted emission spectrum curve in the state of no tested power supply EMI filter access;
c) The two power supply switching devices are switched to ensure that one path connected with the tested power grid EMI filter is connected;
d) And repeating the step b), and testing the current conducted emission spectrum curve and the voltage conducted emission spectrum curve in the state that the tested power grid EMI filter is connected.
3. The method of claim 1, wherein: the acquisition device comprises two frequency spectrometers, wherein the first frequency spectrometer is connected with an L line output by the isolation transformer for the warship through a current joint, and the second frequency spectrometer is connected with the L line and an N line output by the isolation transformer for the warship through a voltage joint.
4. The method of claim 1 or 2, wherein: when the voltage and current conducted emission spectrum curve under the state that the power grid EMI filter is not tested is tested, the current conducted emission spectrum curve I under the state of no filtering is obtained by using the first frequency spectrograph and the current probe for testing CE1 (ii) a Obtaining a voltage conduction emission spectrum curve U in a non-filtering state by using a second frequency spectrograph and a voltage probe for testing CE1 (ii) a When testing voltage and current conducted emission in the state of being connected with the tested power grid EMI filter, a current conducted emission spectrum curve I in the state of no filtering is obtained by using a first frequency spectrograph and a current probe for testing CE2 (ii) a Obtaining a voltage conduction emission spectrum curve U in a non-filtering state by using a second frequency spectrograph and a voltage probe for testing CE2 ；
At U CE1 And U CE2 The frequency spectrum curve of the variable frequency power supply is read, and the voltage values of the switching frequency and the harmonic wave of the variable frequency power supply are respectively U CE1N And U CE2N N denotes the harmonic order, i.e. N =1 denotes the fundamental wave of the switching frequency, N =3 denotes the 3 rd harmonic of the switching frequency;
when calculating the voltage insertion loss, the voltage insertion loss U is calculated according to the following formula dB ：
U dB ＝U CE1N -U CE2N ；
When calculating the current insertion loss, the current insertion loss I is calculated according to the following formula dB ：
I dB ＝I CE1N -I CE2N 。
5. The method of claim 1, wherein: and the load formed by the variable frequency power supply and the load is not less than the equivalent capacity of the tested power grid EMI filter.
6. The method of claim 1, wherein: the switching frequency of the variable frequency power supply is less than 10kHz.
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| CN117420350A (en) * | 2023-11-08 | 2024-01-19 | 广州市德珑电子器件有限公司 | Loss testing method, system, equipment and medium for power filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117420350A (en) * | 2023-11-08 | 2024-01-19 | 广州市德珑电子器件有限公司 | Loss testing method, system, equipment and medium for power filter |
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