The part that would scare me... I suspect the mentioned APC units are probably using Solid State AC Relays.
Most of the more common SSR's tend to leak through... , which can be really dangerous in the wrong application. cheers, s. > "Eric Lemmon" <[EMAIL PROTECTED]> wrote: > > My definition of "seamless" is no interruption at all, which usually means > an on-line UPS in which an inverter runs continuously on a DC supply that > floats on batteries. The APC unit on the link shown in the original posting > must disconnect from one source before connecting to the other source- and > that is not seamless. That said, most equipment that is built to CBEMA > standards will tolerate a power loss of several cycles without crashing, and > each cycle is about 17 milliseconds. Perhaps APC defines the word > "seamless" as "nearly continuous." > > I am amused by APC's assertion that its device is the only unit of its kind > in a 1U rack mount. Perhaps APC hasn't heard about Pulizzi Engineering's > line of asynchronous transfer switches, such as this one: > <www.pulizzi.com/Products/2007_Catalog/2007_Catalog_Page_34.pdf> > The Pulizzi transfer switches have been the "gold standard" in the aerospace > industry for years, and hundreds of them are in service at Cape Canaveral, > Kennedy Space Center, and Vandenberg AFB where super-critical equipment > supports both manned and unmanned space launches. We often use the term > "Pulizzi" as generic, because they are reliable and widely used. > > If there is any possibility that the two incoming power sources may not be > exactly in phase with each other- as when one source may be an engine-driven > generator- a transfer switch that can handle asynchronous sources must be > used. The Pulizzi switch in the link above is such a device, and it is not > cheap! > > 73, Eric Lemmon WB6FLY > >
