>Jerry;
>
>Just to add a few comments from my engineering background without too much detail or theory:
>
>Some user appliances are designed will a very small safety margin in case of a voltage spike. Most equipment of that type is designed for a + or – 10% voltage variation before something will go wrong. A large voltage spike on a primary line may only last for a few microseconds but can destroy equipment.
>
>Traditional Power supplies utilized inductors (chokes) and capacitors to filter alternating current. Even power supplies used by S-100 bus computers used this system. Along came the IBM PC and we began using what is termed “switching power supplies”, that is a direct current is created which does not require the use of inductors. This reduces the size and cost of the power supply. Very large capacitors are used in this configuration, which hold an electric charge for a longer period of time. The length of time is dependent upon the load of the appliance. There are many variables.
>
>It is possible for a power supply to hold a charge long enough (a fraction of a second) if there is a momentary loss of primary power. At the same time a surge can cause a huge voltage spike on the line. This can destroy some appliances such as microwave ovens, computer monitors and televisions, which are very sensitive to voltage spikes of even a few microseconds. A properly designed appliance will allow for this to some extent. Voltage spikes do not have to be very large to damage equipment and some spikes are of large value.
>
>I have peak voltage suppressors on all my equipment to prevent such problems. If you are in an environment, which has commercial users, you should look at power line conditioning equipment or at least voltage suppressors. UPS Backup Power Supplies are also great to help save data. At least they give you a chance to power down gracefully when a power outage lasts for more than a few minutes.
>
>Another problem stems from neutral and ground wire connections. When improperly done these add to primary power problems.
>
>Here is a link on the subject.
>
>http://www.tweety.net/New%20domain/Tech%20Tips/POWERLINES.htm
>
>Tom

Yup.
A good UPS eliminates all of this. An inexpensive surge suppressor, essentially a diode or scr, will stop the spikes, if the powerline has a good grounding wire. All this stuff brings back memories of Physics in college, both with I was a student and later when I taught the subject. The fun part of it was designing circuits using the various laws combined with calculus. I really enjoyed that stuff, especially when the test circuits behaved exactly like the calculations.
JLK