RFI Suppressors
FAQ
What is an RFI Suppressor?
- An RFl Suppressor is a special type capacitor for use on the AC Power Line input to electronic or electrical equipment. It's purpose is to attenuate Radio Frequency Interference signals originated in this equipment and conducted through the AC Line to other equipment supplied by the same branch., These interference signals, if not attenuated, would mutually disturb their operations.
How do they work?
- To prevent such situations, each piece of AC operated equipment must have its RFl signal filtered and attenuated to the levels established by International and National Regulatory Agencies (FCC in the USA). Almost every kind of electronic equipment, such as radio and TV receivers, computers, switch mode power supplies and household appliances generate their own “electrical signature” of Radio Frequency spectrum, depending on individual designs or modes of operation. This spectrum can affect other equipment either by being conducted onto the AC line, or by being radiated by small radio and high frequency “transmitters” hidden in internal circuits and traveling by air to affect the operation of other equipment in adjacent locations. RFI Suppressors are used in filter circuits to attenuate conducted interference.
What makes RFI Suppressors unique?
- You must have realized by now, that RFI Suppressors are very special and that worldwide there are only a few. manufacturers who are capable to provide them to OEM producers We are proud to say that World Products’ RFI Suppressors offer superior characteristics over the competition in the following areas:
- All International Safety Approvals
- High Dv/Dt Levels
- Excellent Self Healing
- Preferred Industry Standard Dimensions
- Available With Modified Lead Configurations
- Flame Retardant Encapsulation (94V - 0)
- Each Lot Tested 100%
- Standard Electrical AQL - 0.065
What kind of equipment uses RFI Suppressors?
- Every newly designed piece of electronic equipment must have its conducted and radiated interference measured and reduced to the levels established by Regulatory Agencies. Depending on the particular design and its other components in the AC line input, various values of capacitance (C) of RFI Suppressors may be required to tune AC line filtering performance for Radio Frequencies appearing in its “electrical signature.” To allow for such tuning our selection of RFI Suppressors consists of 70 (seventy) types.
What kind of conditions must RFI Suppressors withstand?
- These suppressors (which also act as RFI filters) must also endure very harsh conditions existing on the 60 or 50 HZ AC Power line. These conditions include sudden increases of the AC line that may greatly exceed nominal operating conditions large transients with high Dv/Dt edges and lightning. For these reasons, RFI Suppressors must withstand voltages exceeding their nominal voltage ratings. They also must have “self healing” properties, which is the ability of the suppressor to cure itself when the dielectric is punctured due to an abnormal AC line disturbance or lightning strike. Due to these hazardous conditions and stringent requirements, these suppressors must be approved by all important Regulatory Agencies in the USA, Canada and Europe. These Agencies are subjecting RFI Suppressors to strict tests to assure their performance and safe operation on the AC line.
How many different types of RFI suppressors are there?
- There are two (2) basic types of RFl Suppressors:
X2 - Placed Line-to-Line: WXP, WXPC Series
Y2 - Placed Line-to-Ground: WYP, WYE Series
How are they different?
- Suppressor X2 (WXP and WXPC) can be used in electrical circuits between the ?live? wires carrying incoming AC current. They suppress “differential mode” RFI noise. In this location, suppressor damage will not cause any electrical shock hazards and usually will open the fuse and turn the equipment off.
Suppressor Y2 (WYE and WYP), used between lines and grounds to filter “common mode” RFI noise, have higher voltage withstand limits and smaller capacitance values because:
- If damage occurs, they will not activate any safety fuse.
- Even if they are in a perfect condition, there is some current flowing through them from line to equipment ground that would become “hot” if disconnected from the earth grounding. If larger C values were allowed for Y2 suppressors (the largest WYE capacitor has C = 0.022uF, the largest WYP capacitor is 0.1µF), leakage current would be too high for safety standards.
- If lightning should strike the AC power line, Y2 suppressors would be the most likely to be subjected to damage.
- Our X2 suppressor WXPC has a voltage rating of 275VAC, WXP is rated 300VAC.
Y2 suppressors are rated at 250VAC—WYE and 275VAC—WYP.
These Y2 ratings are very conservative for reasons explained above and considering that in production Y2 are tested at 3,000VDC/µsec vs. 2,000VDC for X2.
Similarly, in the lightning simulation test, the Y2 suppressor must be approved at 5KV vs. 2.5KV for X2.
Are Y2 and X2 Suppressors interchangeable?
- Actually, Y2 suppressors could be substituted for X2 suppressors in an across-the-line location, if not for the fact that their C values are usually too small for that. However X2 suppressors should never be substituted for Y2 suppressors
How do I get more technical information on RFI suppressors?
- Contact your World Products salesperson or representative for an RFI Suppressor Data Sheet. It contains all the information you will need. Because of mandatory compliance with FCC, UL, CSA and other International Safety Agencies, most manufacturers have a specialized Engineering Department dealing with RFI matters. These departments have a very good knowledge about the required RFI Suppressors and will know exactly what their needs and requirements are.
What kinds of companies use RFI Suppressors?
- Many OEM companies producing AC operated equipment: computers, computer terminals, radio and television equipment, communication gear, etc. will use RFI suppressors. Even portable equipment companies may need RFI Suppressors for battery chargers and other stationary equipment. Automotive products may be the only example of an unlikely application since automobiles, with-their 12 volt systems, normally would not need, our AC line rated suppressors. However, there can be some applications where there is a need for tough components having a climatic category rating of 56 days in the humidity chamber. Please note that the climatic category rating achieved by WP RFI Suppressors (40/100/56) is among the highest in the industry.
Will RFI suppressors play a part in the future of electronics?
- The prospect for increasing usage of RFI suppressors in the future is excellent. RFI attenuation was first required for consumer products such as television and stereo's in the 1970's, and then it was extended to include computers, and their peripherals: monitors, terminals, printers, etc., in the 1980's. In Europe, household appliances and electric, tools must also meet RFI regulation limits. In the USA, these devices are not yet included in RFI limits, but many companies are implementing them on their own. With the expansion of various new electronic products, this will be a growing and continuous business. Once customers recognize the advantages of buying RFI Suppressors from WP there will be increased demand for equipment currently in production and new designs in development.
What’s new in WP RFI Suppressors?
- In the last two years we expanded our selections of RFI capacitors by adding two new series in X2 and Y2 classes. These are:
- WXPC — X2 Class polypropylene film series similar to WXP series but in reduced compact sizes, covering C values 0.01µF to 1.5µF at 275VAC rating — and extended to large C values: 2.2µF, 3.3µF, 4.7µF and 6.8µF with voltage rating increased to 300VAC. These large C capacitors are intended for large industrial filters applications.
- WYP — Y2 Class polypropylene film series covering C values 0.01µF to 0.1µF and rated 275VAC. These capacitors can be used in applications where 250VAC rating of our WYE series was not high enough and/or where C values larger than 0.022µF are needed. WYP provides as well an alternative choice of dielectric polypropylene versus polyester film of WYE series.
Also, we upgraded voltage rating on WXP series from 275VAC to 300VAC. This allows its usage as interphase capacitors in AC power systems where nominal interphase voltage is 277VAC.
In summary, we now have a well balanced offering of RFI capacitors of X2 and Y2 classes, available in polypropylene and polyester film versions. Total range of C values extends from 0.001µF (WYE-102M) to 6.8µF (WXPC-685M) with 3 voltage ratings: 250VAC, 275VAC and 300VAC. With such a selection, we can serve all RFI needs that any customer may have. Please contact World Products and put us to the test.
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