Sags & Swells Symptoms - Electronic Equipment

Electronic devices require a more controlled electrical environment than most other loads. This is especially true when it comes to the input voltage. If the source voltage into the power supply varies beyond the device's specifications, then problems can occur.

Recall that a sag or swell is not simply a change in the RMS magnitude, but a change over a discrete period of time. This time interval is important in terms of determining acceptable voltage.

The fundamental issue behind the symptoms related to sags and swells is how much energy is being transferred into the power supply. If inadequate energy is going into the power supply due to a sag, then the DC voltage applied to the integrated circuits drop. If this happens, the device will shut down, lock up, or garble data. If the device shuts down, it will usually restart as soon as enough energy gets back into the supply.

On the other hand, if too much energy goes into the supply because of a swell, it will probably cause damage. Blown power supplies are the most common result of large swells. Obviously, if the power supply fails then the whole device goes down.