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 -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Sunday, August 03, 2008 9:24 AM To: [email protected] Subject: [Repeater-Builder] Re: Switching a Repeater Betwen AC Sources The caveat is in the web page text... [pasted APC web page text] > If the primary power source becomes unavailable, the rack ATS > will seamlessly source power from the secondary source without > interrupting critical loads. [end pasted text] Depends on what your interpretation of "seamless" is... There will be some fractional switching time interruption of the mains power else they have some new/secret method for placing a lot of electronics and energy storage in a 1 RU (rack unit) box. cheers, skipp > Chuck Kimball <[EMAIL PROTECTED]> wrote: > > Laryn: > > Take a look at: http://www.apc.com/products/family/index.cfm?id=14 <http://www.apc.com/products/family/index.cfm?id=14> > > This would do exactly what you want. Don't bother with the new > (Especially at $400), I have an older version picked up off of Ebay here > at the house and it runs great. > Protects against the UPS failing, and since it's got a network > connection I can log into it remotely and actually see the log of when > power dropped out on either side. > > Chuck n0nhj > > > Laryn Lohman wrote: > > Thanks for the great posts so far. > > > > Perhaps I didn't make it clear in my original post--our equipment is > > and always has been plugged into the red receptacle. It was installed > > by hospital electricians a number of years ago for us, and we are the > > sole load on the circuit. It was the recent storm, and presumed > > lightning strike, that tripped the AC breaker in the emergency breaker > > panel in the penthouse where our stuff is. > > > > The point of all this is that the breaker tripped, leaving our > > equipment with no power <duh hehehe>. So I was proposing a method of > > implementing a "backup breaker" in case one breaker trips. My > > proposal is that our normal, daily supply would be the white > > receptacle. If it goes dead, whether from utility failure or breaker > > trip, we have the red receptacle, which will then be ready to feed our > > stuff. > > > > The reason we would not want to be on the red receptacle normally is > > that in case of a lightning strike we are potentially left with a dead > > red from the strike, and dead white if the utility is down. > > Obviously, another strike, after we've switched to the red, kills AC > > totally to our stuff. The presumption is that a breaker probably > > won't trip, even after a strike, if there's not a load of some sort on > > it to complete a path for the "tripping" current. Make sense? > > > > Eric, I think you're on my line of thinking. Good point on keeping > > the greens isolated. > > > > Laryn K8TVZ > > > > > > > > > > ------------------------------------ > > > > > > > > Yahoo! Groups Links > > > > > > > > > > >
