Surge Protectors
in [Repair]
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From: Jim Yanik on 27 May 2010 11:53 zekfrivo(a)zekfrivolous.com (GregS) wrote in news:htlreq$mlf$1(a)usenet01.srv.cis.pitt.edu: > In article > <f026ebce-f1d8-4dc2-83f3-4847ef4dcf64(a)o12g2000vba.googlegroups.com>, > whit3rd <whit3rd(a)gmail.com> wrote: >>On May 26, 2:09=A0am, vjp2...(a)at.BioStrategist.dot.dot.com wrote: >>> Are surge protectors based on grounding or diode clipping? >> >>Both. Most surge suppressors have a conducts-on-overvoltage >>element directly across the line, with a fuse or circuit breaker to >>keep the fire hazard low. Additional elements that connect to the >>protective ground pin are of secondary importance. > > I would argue that. The differential surpressor is fine, but the > common mode surge can do more harm and a lot of noise problems. Using > an isolation transformer makes common mode problems impossible. Its a > direct short to ground. > > greg > > >>The conducts-on-overvoltage element is usually a metal oxide >>varistor, a kind of crude semiconductor breakover diode. it's not a "diode",its just a sintered semi-metallic pellet that conducts once a certain voltage is reached. a "diode" is a P/N junction or a semiconductor/metal junction. > even the cheap suppressors I've bought had 3 MOVs,one for each leg to ground and from one leg to the other. I guess that's a "delta" config. -- Jim Yanik jyanik at localnet dot com
From: whit3rd on 27 May 2010 13:22 On May 27, 8:53 am, Jim Yanik <jya...(a)abuse.gov> wrote: > zekfr...(a)zekfrivolous.com (GregS) wrote innews:htlreq$mlf$1(a)usenet01.srv.cis.pitt.edu: > >>> Are surge protectors based on grounding or diode clipping? > > >>Both. Most surge suppressors have a conducts-on-overvoltage > >>element directly across the line, with a fuse or circuit breaker to > >>keep the fire hazard low. > >>The conducts-on-overvoltage element is usually a metal oxide > >>varistor, a kind of crude semiconductor breakover diode. > > it's not a "diode",its just a sintered semi-metallic pellet that conducts > once a certain voltage is reached. > a "diode" is a P/N junction or a semiconductor/metal junction. The metal oxide in a MOV is certainly a semiconductor. The breakover is due to avalanche multiplication rather than minority injection. The oldest ones were SiC (basically, just grinding wheels with electrodes bolted on). It has two leads, so it's a diode. It's made with a semiconductor, so it's a semiconductor diode. It isn't a rectifier diode, though. DIAC and current regulator two-terminal devices are also diodes, but aren't simple PN junction types (don't really rectify). Vacuum tubes are sometimes diodes, too (like my microwave oven's magnetron). > even the cheap suppressors I've bought had 3 MOVs,one for each leg to > ground and from one leg to the other. I guess that's a "delta" config. The protective ground connection is, in most situations, carrying no current. The MOVs that connect to that protective ground are not so much protecting the plugged-in device, as they are dumping transient energy in the building's wiring (protecting the building rather than the appliance). The internal suppressors on lots of consumer equipment only have one MOV, across the line, not the full trio that is common in third- party suppressor modules.
From: GregS on 27 May 2010 15:29 In article <6a2cfce3-46ea-472c-834d-cb47729d1d63(a)v18g2000vbc.googlegroups.com>, whit3rd <whit3rd(a)gmail.com> wrote: >On May 27, 8:53=A0am, Jim Yanik <jya...(a)abuse.gov> wrote: >> zekfr...(a)zekfrivolous.com (GregS) wrote innews:htlreq$mlf$1(a)usenet01.srv.= >cis.pitt.edu: > >> >>> Are surge protectors based on grounding or diode clipping? >> >> >>Both. =A0Most surge suppressors have a conducts-on-overvoltage >> >>element directly across the line, with a fuse or circuit breaker to >> >>keep the fire hazard low. > >> >>The conducts-on-overvoltage element is usually a metal oxide >> >>varistor, a kind of crude semiconductor breakover diode. >> >> it's not a "diode",its just a sintered semi-metallic pellet that conducts >> once a certain voltage is reached. >> a "diode" is a P/N junction or a semiconductor/metal junction. > >The metal oxide in a MOV is certainly a semiconductor. The breakover >is due to avalanche multiplication rather than minority injection. >The oldest >ones were SiC (basically, just grinding wheels with electrodes bolted >on). >It has two leads, so it's a diode. It's made with a semiconductor, so >it's a semiconductor diode. It isn't a rectifier diode, though. >DIAC and current regulator two-terminal devices are also diodes, >but aren't simple PN junction types (don't really rectify). >Vacuum tubes are sometimes diodes, too (like my microwave oven's >magnetron). > >> even the cheap suppressors I've bought had 3 MOVs,one for each leg to >> ground and from one leg to the other. I guess that's a "delta" config. > >The protective ground connection is, in most situations, carrying no >current. The MOVs that connect to that protective ground are not so >much >protecting the plugged-in device, as they are dumping transient energy >in >the building's wiring (protecting the building rather than the >appliance). >The internal suppressors on lots of consumer equipment only have >one MOV, across the line, not the full trio that is common in third- >party >suppressor modules. > I thought there were NO supressors in most consumer equipment because its a liability. Its the line to ground noise and surges that cause TTL computer type equipment to BOMB OUT. Ground has everything to do with functioning circuits, that use ground for reference. Of, course, its best not to use ground for reference. greg
From: Jim Yanik on 27 May 2010 16:44 zekfrivo(a)zekfrivolous.com (GregS) wrote in news:htmh5b$rcn$1(a)usenet01.srv.cis.pitt.edu: > In article > <6a2cfce3-46ea-472c-834d-cb47729d1d63(a)v18g2000vbc.googlegroups.com>, > whit3rd <whit3rd(a)gmail.com> wrote: >>On May 27, 8:53=A0am, Jim Yanik <jya...(a)abuse.gov> wrote: >>> zekfr...(a)zekfrivolous.com (GregS) wrote >>> innews:htlreq$mlf$1(a)usenet01.srv.= >>cis.pitt.edu: >> >>> >>> Are surge protectors based on grounding or diode clipping? >>> >>> >>Both. =A0Most surge suppressors have a conducts-on-overvoltage >>> >>element directly across the line, with a fuse or circuit breaker >>> >>to keep the fire hazard low. >> >>> >>The conducts-on-overvoltage element is usually a metal oxide >>> >>varistor, a kind of crude semiconductor breakover diode. >>> >>> it's not a "diode",its just a sintered semi-metallic pellet that >>> conducts once a certain voltage is reached. >>> a "diode" is a P/N junction or a semiconductor/metal junction. >> >>The metal oxide in a MOV is certainly a semiconductor. I never said otherwise. but it's NOT a "diode". >>The breakover >>is due to avalanche multiplication rather than minority injection. >>The oldest >>ones were SiC (basically, just grinding wheels with electrodes bolted >>on). >>It has two leads, so it's a diode. No,it's not. from the Free Dictionary; 1.An electronic device that restricts current flow chiefly to one direction. 2. An electron tube having a cathode and an anode. ... Other Google examples for "diode definition" are essentially the same. A thermistor is another semiconductor,with two leads,yet NOT a "diode",but a resistor.An MOV is closer to "resistor" than "diode". a Polyfuse is another semiconductor with two leads,yet not a "diode". >>It's made with a semiconductor, so >>it's a semiconductor diode. It isn't a rectifier diode, though. >>DIAC and current regulator two-terminal devices are also diodes, >>but aren't simple PN junction types (don't really rectify). >>Vacuum tubes are sometimes diodes, too (like my microwave oven's >>magnetron). >> >>> even the cheap suppressors I've bought had 3 MOVs,one for each leg >>> to ground and from one leg to the other. I guess that's a "delta" >>> config. >> >>The protective ground connection is, in most situations, carrying no >>current. The MOVs that connect to that protective ground are not so >>much >>protecting the plugged-in device, as they are dumping transient energy >>in >>the building's wiring (protecting the building rather than the >>appliance). MOVs -shunt- surge energy to ground,through the wiring. sometimes,they cannot handle the energy,and blow apart.I've had to replace more than a few of them,living in the Lightning Capitol of the US,central Florida. Sometimes,the surge energy finds a better path through the protected device,with unfortunate results. >>The internal suppressors on lots of consumer equipment only have >>one MOV, across the line, not the full trio that is common in third- >>party >>suppressor modules. >> > > I thought there were NO supressors in most consumer equipment > because its a liability. no,just an extra cost. plus,after they absorb a strike,they often need replacement,along with the blown fuse. > > Its the line to ground noise and surges that cause TTL computer type > equipment to BOMB OUT. Ground has everything to do with functioning > circuits, that use ground for reference. Of, course, its best not to > use ground for reference. > > greg > even with floating circuits,a lightning strike will find some path to ground. Probably one that is destructive. -- Jim Yanik jyanik at localnet dot com
From: whit3rd on 28 May 2010 00:27
On May 27, 1:44 pm, Jim Yanik <jya...(a)abuse.gov> wrote: > zekfr...(a)zekfrivolous.com (GregS) wrote innews:htmh5b$rcn$1(a)usenet01.srv.cis.pitt.edu: > >>> >>The conducts-on-overvoltage element is usually a metal oxide > >>> >>varistor, a kind of crude semiconductor breakover diode. > > >>> it's not a "diode",its just a sintered semi-metallic pellet that > >>> conducts once a certain voltage is reached. > >>> a "diode" is a P/N junction or a semiconductor/metal junction. > > >>The metal oxide in a MOV is certainly a semiconductor. > > I never said otherwise. but it's NOT a "diode". > from the Free Dictionary; > 1.An electronic device that restricts current flow chiefly to one > direction. 2. An electron tube having a cathode and an anode. ... > > Other Google examples for "diode definition" are essentially the same. How sad. Diode, meaning two electrodes... applies to a variety of semiconductor devices, and vacuum tubes. Not just rectifiers, but tunnel diodes and gunn diodes and those self-blinking LEDs (really oscillator integrated circuits with a lamp). The dictionary is wrong. MOVs are semiconductor devices equivalent to avalanche (Zener) diodes, but without any forward-bias conduction. They're semiconductor diodes in all senses of the words. |