SPD Basics Series Surge Suppression "104" 

Several of our competitors call it EMI/RFI filtering. One competitor uses the statement "AC Sine wave True Tracking Filter with EMI/RFI Filtering up to -50dB from 10 kHz to 100 MHz" on their spec sheets. From a transient voltage surge suppression perspective this statement is confusing to the point that it does not make sense.

Sine wave tracking or as we call it today Frequency Responsive CircuitryTM is not intended to be just an EMI/RFI filter. Conversely circuits designed specifically for the purpose EMI/RFI Filtering may not be effective as a sine wave tracking (frequency responsive) transient voltage surge suppressor. The fact is that while they are both filter circuits they have different purposes and their performance is stated in a different manner to reflect that difference in purpose.

RFI circuits are normally a broadband type of filter circuit and performance is measured in -dB numbers based on a beginning point. For each -3dB the RFI energy has been reduced by half. The purpose of the EMI/RFI circuits is to reduce noise that resides within a wide frequency spectrum on the protected circuits and is inherently more effective at some frequencies than others dependent on the design of the filter and the components it contains.

Sine wave tracking (frequency responsive) transient voltage surge suppression circuits are designed to reduce transient surge voltage at the frequency range where ringing transients are most commonly found. The performance testing for this type of circuit is performed at 100 kHz. Since it is a filter circuit it responds to rapid changes in frequency and serves to reduce the amount of that deviation from the normal 60 HZ sine wave. Because the purpose of the circuit is transient voltage surge suppression, the performance is measured in volts.

Since these filters serve two different functions, our spec sheets state the performance of those circuits in a separate area in the form that is proper for those filters. EMI/RFI performance is listed on the front side of the spec sheet where it says "Insertion Loss Data". It is listed at different levels to give you an idea of how it varies according to different frequencies between 10 kHz and 1 MHz. Frequency responsive circuitry (sine wave tracking) performance data is found in the let-through voltage section of the spec sheet of our products under the Category A column and the test impulse is introduced at the 270 degree point of the sine wave. We are one of the very few manufacturers who even publish this data.

The rest try to hide behind their EMI/RFI filters and call it sine wave tracking. Unless the manufacturer gives you let-through voltage performance data for ring wave transients, you have no way to determine the level of protection that their product provides. Not only do we at SSI provide this data on our spec sheets, the test result data has been 3rd Party Certified. We are the ONLY manufacturer who does this.

SSI does not create marketing issues to help us sell products. We don't have to. Between man and Mother Nature there are enough real issues that need to be addressed. Our job is to simply make a quality product that provides the most important thing a surge suppressor can do and that is low let through voltages. Anything else is secondary!