In some UPS units (as well as surge protectors), I have seen MOVs between Live and Earth, and between Neutral and Earth, not to mention the one between Live and Neutral. Will MOVs between Live and Earth, and between Neutral and Earth provide extra protection?
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My first choice in quality Japanese electrolytics is Nippon Chemi-Con, which has been in business since 1931... the quality of electronics is dependent on the quality of the electrolytics. -
Re: MOVs between L-E and N-E
They may provide additional protection, but are you sure they're not the usual EMI/RFI filter ceramic discs? They look very similar to MOVs, often with the same blue or yellow epoxy coating. -
Re: MOVs between L-E and N-E
A MOV is typically designated on a PCB by MOV, ZNR, TNR or Z. There were 3 such designations on a UPS PCB, which corresponded to MOVs.My first choice in quality Japanese electrolytics is Nippon Chemi-Con, which has been in business since 1931... the quality of electronics is dependent on the quality of the electrolytics.Comment
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Re: MOVs between L-E and N-E
Apparently there are more surges between L-E and N-E than between L-N, so I guess that the extra MOVs help.Comment
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Re: MOVs between L-E and N-E
In American 3-wire installations (L-N-E), the Neutral and Earth are connected at the breaker box. However, the amount of current that flows in the hot wire (Line) also flows in the return wire (Neutral). Depending on the amount of current flow, the distance to the breaker box, and the wire gage, the Neutral can actually be a couple of volts above ground (Earth) due to voltage drop (I*R). No current should flow in the ground (Earth) lead; if it does, it means that the Neutral is open, or the Neutral and ground are shorted at the device. Also, the length of wiring between the breaker box and the outlet acts as an antenna, and is particularly susceptible to induced voltage (i.e., lightning strikes nearby). Therefore, the L-E MOV functions as a backup to the L-N MOV, and the N-E MOV provides the same protection as the L-E MOV on the neutral line. For the same reason, there are shunt capacitors on both L-E and N-E, so that any stray/induced voltages are removed from both lines, and the power supply line is balanced.
Are European installations similar (willawake, Rainbow, cods69)?Comment
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Re: MOVs between L-E and N-E
See http://fr.wikipedia.org/wiki/Neutre_...ectricit%C3%A9)
(you can ignore the text (as I did because I don't know french), just see the pictures)
Here in Slovakia, TN-C and TN-S are most widely used. TN-S is used in most modern buildings, TN-C in older.Comment
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Re: MOVs between L-E and N-E
With extreme care, voltage measurements between Live/Neutral and Live/Earth should be almost the same. Measuring between Neutral and Earth should measure no more than 0.5V (depending on how big the building is), because Neutral and Earth are tied together at the switchboard before any RCD/GFCI/ELCB (safety switch) device. If there is a significant voltage between Neutral and Earth, call a licensed electrician as soon as possible to remedy this fault.
I think one of the reasons why MOVs are between Live and Earth, as well as between Neutral and Earth because there may be buildings with the earth wire not tied to the neutral wire in the switchboard.My first choice in quality Japanese electrolytics is Nippon Chemi-Con, which has been in business since 1931... the quality of electronics is dependent on the quality of the electrolytics.Comment
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I have a whole home surge protector (Eaton CHSPT2SURGE). This is the lower end model as compared to the CHSPT2ULTRA. When I took it apart, I noticed it's basically the same PCB as the higher end model, just missing the extra MOVs for higher capacity. Coincidentally, I have a pack of brand new Bourns 20D241K MOVs laying around:
https://www.digikey.ca/en/products/d...0D241K/2799098
The only thing I noticed is that these Bourns MOVs are not thermally protected with a fuse. I'm wondering if it's safe to just simply install these extra MOVs for extra capacity,... -
I bought one of these as it was the only one I could find that is compact enough to fit in my toolbox (though I've since found KSGER make a substantially safer looking one). It's one of those fan-in-handle things that has the 230V element in the handle. Quecoo briefly sold a similar unit but discontinued it.. maybe they couldn't find solutions to these problems. I'm aware these fan-in-handle things are garbage compared to a good air pump station but I only really use this for occasional QFN work etc.
I did not realise at the time of buying that its design is... interesting, to say... -
I have repaired a Sign WiFi Smart Plug with model number: SNSM-WASINGLE sold by Spares Nordic AB in Sweden.
The fault condition was that the device gave no signs of life: pressing the push button did not cycle the internal relay and the blue LED did not come on and it was not seen on the WiFi network.
The fault was very simple, capacitor C3 on the PCB with writing "KSJ" and "LOWESR" had literally blown its top off, after replacing it the device works fine again!
As I find linear high voltage regulator designs interesting I drew up the attached schematic... -
Good day folks. Recently my company has, in a kinda-sorta-way, nominated me to join the "security systems team" which involves going to various sites to install alarm systems and CCTV cameras...not the best of positions, since I've gravitated pretty far away from my beloved laptop and electronics repair, but at least the pay is adequate (enough....for now) and I'll definitely be moving back to those once my boss decides it's the right time, but I digress.
The reason I'm asking about how mains grounding works is because more often than not, I have to connect up the alarm... -
Hi All,
I have acquired a hefty isolation transformer for use on(under) the bench and have a question about earth bonding.
Apart from the live & neutral connections, should the transformer itself be connected to mains earth?
If so, should the device under test, powered by the IT also be connected to the transformer earth?
Many thanks in advance.
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