Jeff, Right you are! The Square D circuit breakers found in home improvement stores are the common "QO" or "Homeline" variety, which have a fast magnetic trip action. Commercial electrical supply houses either stock or can get on short notice the QO-HM (plug-in) or QOB-HM (bolt-on) circuit breakers with the high magnetic action. Large-frame breakers in the 100 to 1600 ampere class usually have adjustable delay and trip points. Here's the blurb from the Square D catalog:
"QO-HM and QOB-HM high-magnetic circuit breakers are recommended for area lighting (athletic fields, parking lots, outdoor signs, etc.) when using lamps of inherent high inrush current, individual dimmer applications, or other applications where high inrush current exceeds standard tripping conditions. These circuit breakers are available in one-pole 15 and 20 amperes only. QO-HM and QOB-HM circuit breakers are physically interchangeable with standard QO and QOB circuit breakers and accommodate the complete range of QO accessories." I am amazed that commercial and cellular site owners and operators are too often unaware of the high inrush currents drawn by large power supplies at startup. Depending upon where in the AC cycle the switch is closed, a typical transformer-input power supply can draw well over 100 amperes for an instant. A lot of electricians who should know better are not aware of "special application" circuit breakers, and routinely install the standard breakers on every job. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Wednesday, January 17, 2007 6:52 PM To: [email protected] Subject: RE: [Repeater-Builder] Re: Power Supplies going up in smoke (non filtered) > Even the common plug-in circuit breakers made by Square D, > Cutler-Hammer, and others are available in high-inrush > versions- but you > won't find them at Home Depot. Yeah, I know. I've always heard them called "hi-mags", meaning higher magnetic (current) trip point as compared to standard breakers, yet still have the same thermal trip point for longer-term protection. I seem to recall larger industrial breakers having a built-in delay for inrush current trip protection. You're the power guy, you tell me :-) <snip> --- Jeff
