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4.0 Principles of operation
4.1 Noise and surge suppression
Your PowerCell contains high performance EMI/RFI (Electro-Magnetic and
Radio Frequency Interference) noise and surge suppression circuitry to protect
your computer equipment. The PowerCell provides this suppression continu-
ously, whether or not it is turned on. Normally, your PowerCell suppresses noise
and surges without your notice; that is, the UPS doesn’t transfer your load to its
internal power source. Instead, the suppression circuitry reduces the amplitude
of noise and surges to a level well below that which can be tolerated by your
relatively delicate computing equipment.
The illustration above shows what a typical “medium” amplitude surge or spike
looks like when present on the utility voltage. Surges up to 15 times larger than
this are easily suppressed by the PowerCell. Surges are commonly caused by
nearby lightning activity and motor load switching created in air conditioners,
elevators and heat pumps.
The illustration above shows what EMI/RFI noise looks like when present on the
utility voltage. The PowerCell “filters” out this noise with components whose
electrical resistance is very high at radio frequencies. EMI/RFI noise is com-
monly created by the same activity which produces surges but can also be caused
by nearby radio transmitters and blinking neon bulbs and signs.