This was originally posted on APC forums on 8/1/2009
The electrical engineers know that a sudden change in the state of the electrical current is one of the many causes of voltage surges. One of these sudden changes in the state of the the current slow occurs inside every UPS, specially the cheaper ones.The component that causes this is the very well known, relay. This information is available in one of the Schneider Electric document about voltage surges available at:
"A sudden change in the established operating conditions in an electrical network causes transient phenomena to occur. These are generally high frequency or damped oscillation voltage surge waves (see Fig. J1).
They are said to have a slow gradient: their frequency varies from several ten to several hundred kilohertz.
Operating voltage surges may be created by:
- The opening of protection devices (fuse, circuit-breaker), and the opening or closing of control devices (*relays*, contactors, etc.)
- Inductive circuits due to motors starting and stopping, or the opening of transformers such as MV/LV substations
- Capacitive circuits due to the connection of capacitor banks to the network
- All devices that contain a coil, a capacitor or a transformer at the power supply inlet: *relays*, contactors, television sets, printers, computers, electric ovens, flters, etc.
My Question is:
What APC do to deal with this problem in all products that uses relays like UPSes, Voltage regulators, Audio/Video power Conditioners... I've once read that there are many techniques to solve this problem, but that there are very cheap products, specially those made in third world countries that do not do anything to avoid surges coming out of relays...