Clamps are necessary if you don't want the AC mains shorted to ground for each transient event.
MOV's are the most commonly used suppressors for the AC line. Use MOV's rated at higher than the peak AC voltage expected on the mains. Clamping voltages are typically in the 300 to 500V region; however, they will handle a good deal of energy in a single shot. Some manufacturers use strings of silicon clamping devices, but thier charateristics after packaging, lead lenghts, etc... end up being very much like MOV's. The big disadvantage is they are rated for a maximum amount of current and if you go over the number even slightly, they'll blow. Avalanche devices in series with a resistor or clamp are sometimes used, but not as effective as a simple MOV..... Mike Hopkins KeyTek > -----Original Message----- > From: Robert Macy [SMTP:[email protected]] > Sent: Tuesday, January 11, 2000 7:26 PM > To: Ken Javor; [email protected] > Subject: Re: transient suppression > > > Ken, > > Rule of thumb which hopefully is accurate: > > MOV's have a discrete lifetime (like 10 cycles at full rating) before > they're gone. > > In order of joules absorbed versus package size: > Glass tubes, MOV's, silicon (from huskiest to weakest) > > For turn on time: > silicon, MOV's, glass tubes (from fastest to slowest) > > The glass tubes absolutely take a discrete amount of time before they're > "on" > > The voltage across the MOV's can really go very high as they're coming on > - > like 3 times they're rating voltage. The overshoot depends upon the rise > time of the incoming. > > Performance in the system depends a great deal upon the lead length, > layout > etc for real effectiveness. > > - Robert - > > > -----Original Message----- > From: Ken Javor <[email protected]> > To: [email protected] <[email protected]> > Date: Tuesday, January 11, 2000 3:32 PM > Subject: transient suppression > > > > > >When choosing transient suppression for power line input to equipment, > what > >are the choices (MOVs, silicon TVS, glass discharge tubes, others) and > what > >are the trade-offs? Thank you. > > > > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
