Nå er det vel ikke "kvaliteten på råstrømmen" som bestemmer virkningen av ett emc filter.
En kan jo også kjøpe "proff emc filter" fra Schaffner til nær 10 000 kr pr stk.
(Isotek har vel 6 stk filtre i boksen) uten at ett "proff emc filter trenger være noen sukkses .
Var nylig i kontakt med Nkom (tidligere støykontrollen) ang. støy.
Snakket da også litt om emc filtre.Svaret var det samme som JMK sier.
Filteret skal tilpasses kilde og last impedans,eller kan virkning slå i alle retninger,
noe som er diskutert ved flere anledninger her på sentralen uten at årsaken
til at noen får positiv effekt og andre får så negativ effekt av bl.a innebygde filtre
i apparatene at de blir fjernet er kommet tydelig frem.
EMI / RFI Frequently Asked Question
What is an EMI filter?
An EMI filter is a passive electronic device used to suppress conducted interference present on any power or signal line. It may be used to suppress the interference generated by the device itself as well as to suppress the interference generated by other equipment to improve the immunity of a device to the EMI signals present within its electromagnetic environment. Most EMI filters include components to suppress both common and differential mode interference. Filters can also be designed with added devices to provide transient voltage and surge protection as well as battery backup.
How does an EMI filter work?
An EMI filter has a high reactive component to its impedance. That means the filter looks like a much higher resistance to higher frequency signals. This high impedances attenuates or reduced the strength of these signals so they will have less of an effect on other devices.
What criteria are used to select the proper EMI filter?
The proper selection of an EMI filter encompasses the entire electromechanical configuration of the filter. The filter's mechanical footprint including mounting and terminations may impact the effectiveness of the filter in your system. Primary considerations also include leakage current, insertion loss, rated voltage and current, and agency approvals required for proper usage in the end application.
We do not anticipate the standard catalog products to fulfill every application and welcome the opportunity to customize any product to best suit your needs. For additional information, please reference our electronic or print catalogs.
How does the 50 Ohm data compare with actual performance in my system?
The 50 Ohm insertion loss data which appears in our catalog represents an industry standard to allow comparison of different manufacturers' products against a known standard. Since filters are source and load impedance sensitive and the actual load impedance varies greatly from system to system, often a test is the easiest way to determine the actual performance within a specific system.
Insertion Loss Testing
Filters are generally specified with insertion loss performance data. Insertion loss is defined as a ratio of the signal level in a test configuration without the filter installed (V1) to the signal level with the filter installed (V2). This ratio is generally described in db according to the following equation:
Insertion loss (db) = 20 log (V1/V2)
Filters are sensitive to source and load impedances so the exact performance of a filter in a circuit is impossible to precisely predict. Comparisons, however, of filter performance are possible if the insertion loss measurements are made with fixed source and load impedances. 50 ohms is the universally accepted measurement impedance. This data is currently specified as common-mode or differential-mode. Common-mode simply put, is a measure of the filter performance on signals that originate between the power lines and chassis ground. Differential-mode is a measure of the filter performance on signals that originate between the "hot" and neutral power lines. Common-mode insertion loss is measured by connecting the line and neutral terminals together and using the test configuration of figure 1. Differential-mode insertion loss is measured by using the 180 degree power splitters and using the test configuration of figure 2.
