New Performance Standards for Surge Protectors

The following graphic represents a comparison of standard oscilloscope traces. The MOV based surge protector (left) and a Brick Wall Surge Protector (right) are both experiencing a 1200V, 450A surge.

MOV based surge protector vs. Brick Wall surge protector oscilloscope trace

INSTANTANEOUS RESPONSE TIME

At the heart of our surge protectors is the inductor. This is a passive component that is in series. It does not have to 'turn- on' and it represents the only path the surge current can take to get to the load. It reacts instantaneously. Almost all other surge protectors are in parallel. After a certain voltage threshold is reached the shunt elements create a short circuit diverting the surge current away from the load. In effect other surge protectors are nothing more than switching devices. Any switch, no matter how good, is going to take time to go from an opened to a closed position.

CLAMPING LEVEL 2 VOLTS ABOVE THE SINEWAVE PEAK

MOV’s are preset to clamp at certain voltage thresholds (usually around 220V). The manufacturers walk a fine line here because too low a level and the MOV turns on more and wears out sooner. Too high a level and more unwanted current has access to the load. Even more importantly, marketing rhetoric is sacrificed. Our Series Mode surge protectors have active tracking; a 180µf electrolytic capacitor constantly tracks the sinewave peak, whatever the powerline voltage. Any rise above this reference level is immediately clamped to this level

LET THROUGH VOLTAGE <400V

Voltage that gets by a surge protector to the load is called the let through voltage. The lower the let through voltage the better. The above oscilloscope trace of a Brick Wall surge protector shows a let-through voltage of 192V for a 1200V transient. That represents an additional 20V above the sinewave peak (the sinewave peak is normally 172V). When we had our products UL listed under UL 1449 Second Edition, the protocol called for a let through voltage of less than 330V during a single surge of 6000V, 3000A. To take it a step further, we also had UL endurance test our surge protectors with one thousand 6000V surges and the let through never exceeded 400V. We believe this represents the lowest let through voltage of any surge protector in the industry.

SLEW RATE

Slew Rate is the rate of change of voltage in volts per microsecond. The faster the slew rate the more readily the overvoltage will couple to nearby datalines. Notice the ascending slew rates of the MOV-based surge protector oscilloscope traces. This is representative of the voltage that 'hits' the load before clamping. A quick rise such as this can represent quite a 'jolt' to the equipment. The trace of our surge protector unit shows a negligible slew rate. Again, we believe this represents a new industry standard for surge protectors.