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Re: AC Voltage
See my answers below in red: When in doubt, keep it simple, make sure your protection devices have all the proper connections to work, make sure your building wiring is strong enough to support your application (wiring size, breaker type and size, panel wiring, panel balance, etc. etc. etc.), and when in doubt - ask. On Sat, May 18, 2024 at 9:56?AM Johannes wrote:
Yes, getting a working ground is an important thing to fix.
Attaching to interior piping of a building was used in the past because that copper pipe ran outside into the actual ground. However, it is not a good way to make a ground connection because there are many ways it can be ineffective or dangerous.And - you might not have a copper pipe going outside anymore. My son had his house repiped and the copper going outside was replaced with PEX. What you need is to have the ground circuit actually connected to an EARTH return - which means a "ground" rod driven into the ground, near the electrical panel, with a heavy gauge wire connecting the rod to the panel. Grounds within the building also need to be wired and not assumed to be connected by conduit.
Wild electricity is an interesting way to look at it!? The purpose of the ground in these machine tools applications is to divert a live circuit to a safer place - ground. For example, suppose your motor overheats and the insulation is damaged. It is possible that the damaged insulation lets the live power to the motor flow to the case of the motor. If someone were to touch the live circuit by touching the motor housing or something that is bolted to the motor and then also touch something that has a actual ground connection, it is possible for current to flow between one touch to the other. If it is mains power, it can be lots of voltage and lots of current. While the fuse might blow when you become the bridge between hot and ground, more likely is that you would get a shock and worse - and the fuse wouldn't blow. A GFCI (Ground Fault Circuit Interrupter) breaker would have a better chance of stopping you from becoming the fusible link than a fuse. An AFCI (Arc Fault Circuit Interrupter) breaker will also be useful when dealing with leakages as it can detect leakage from more than just ground.
Grounds don't make the AC more stable, they just make a return path for errant current. The quality of the AC coming in is governed by the power transformer that connects to the power company, the wiring along the way, balancing of the loads, etc. While phases are referenced to ground, locally it might be different and this topic is a bit more than I want to tackle here.? We had a case where a link in a meter corroded (really old meter, really old house (knob and tube in places still live), and something took out the circuit in such a way that the 240 coming in to the old house didn't have a neutral reference that was solid One side had 40v and the other 200v. That was a power company call but a bunch of equipment was destroyed by the overvoltage situation (including a couple of MOV surge protectors).
Many MOV circuits are using the ground as the place to dump the transients. In practice, this can have unintended consequences if the ground return isn't really good. Power strips with cords and MOVs work only if the ground in the building wiring is solid and not tied to neutral anywhere but where it is supposed to be. If the return path of the transient is weak, the the electricity will find a better path and that might be more problematic.? Rule to follow - no extension cords on surge protecting power strips.? Why? Because now you are hoping the ground connection on the power strip with a surge protector has a good ground connection and it it doesn't as it adds impedance to the circuit and that can make things worse (pulses decrease, but pulse width lengthens). Ground is a reference point. We call it ground because that is what was used
and is still used
for many applications. In power circuits, it is useful to think of have a hot line, a return line, and a ground line. Inside electronic systems we also think of things the same way, though we might refer to the ground of the system to actually be the return and an actual ground connection is used a different way.
-- Buffalo John |
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Re: AC Voltage
Here part cost $0.15 each? Shipping? is around $6.00 so buy more than one for next time. The good news about part is only voltage you look at for most electronics.??
If you use whole like use for solar systems that is real big one with price to match.? https://www.jameco.com/z/V130LA5-James-Electronics-Varistor-205V-2500A-Surge-Through-Hole-10mm-Disc_667041.html?CID=MERCH |
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Re: AC Voltage
The Varistor use today every where today beyond the mini lathes and DRO'S.? They are not plug in like fuse.?
It is found on the other side of fuse or breaker. You have disconnecte to test the part.? If still good the VOM will read very high ohms.? If bad zero ohms.? It is only a safety part and does nothing till you have voltage spike.? Some will just cut the part out remember if do this you power strip with a Varistor built in.? If you do welding you can trip this Varistor.? |
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Re: AC Voltage
¿ªÔÆÌåÓý
AC is an important subject, and I thank for all input.
Please keep on teaching us:?
Most of us know that the Earth cable (GND)? is important.
However, many (include me) dont have it in the workshop. (it will be fixed soon)
What is the main function of this cable that we connect to a cupper pipe (not steel) or into a cupper plate in the garden?
Is it that wild electricity shall blows the Fuse before it blows me?
Make a better stable AC ?
To be a reference point for what MOV etc. is doing ?
/johannes
From: [email protected] <[email protected]> on behalf of BuffaloJohn <johndurbetaki@...>
Sent: Saturday, May 18, 2024 9:27 AM To: [email protected] <[email protected]> Subject: Re: [7x12MiniLathe] AC Voltage ?
Buried power distribution helps to reduce the chance that a lightning strike will travel into the building. However, not all power distribution is buried, it is above ground some distance away from where it goes underground and
that is where transient can be injected. To protect against this, the power company has lightning arrestors that they install to protect their equipment (transformers, etc.). This reduces the transient that enter a building, but does not eliminate them.
As for the 40 year old TVS, you think
it is still good, but how do you really know? Have you examined the MOVs? We have seen open circuit MOVs as failures and as such, the light that says it is still working gives a false indication. If you look at the circuit of a three pin MOV, you can see how
failure as an open will allow the third leg to let the indicator still light. The specs you list are the TVS specs, not the specs of the devices plugged into the building power distribution circuit.
On Sat, May 18, 2024 at 7:40?AM Pierre-Raymond Rondelle via
<pierreraymondrondelle=[email protected]> wrote:
-- Buffalo John |
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Re: AC Voltage
Buried power distribution helps to reduce the chance that a lightning strike will travel into the building. However, not all power distribution is buried, it is above ground some distance away from where it goes underground and that is where transient can be injected. To protect against this, the power company has lightning arrestors that they install to protect their equipment (transformers, etc.). This reduces the transient that enter a building, but does not eliminate them. As for the 40 year old TVS, you think it is still good, but how do you really know? Have you examined the MOVs? We have seen open circuit MOVs as failures and as such, the light that says it is still working gives a false indication. If you look at the circuit of a three pin MOV, you can see how failure as an open will allow the third leg to let the indicator still light. The specs you list are the TVS specs, not the specs of the devices plugged into the building power distribution circuit. On Sat, May 18, 2024 at 7:40?AM Pierre-Raymond Rondelle via <pierreraymondrondelle=[email protected]> wrote:
--
Buffalo John |
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Re: AC Voltage
¿ªÔÆÌåÓý1- MOV failure mode is short circuit, not open circuit. Never put such a device on the fridge or a freezer line ! 2- Use exclusively MOVs on AC lines Of course, the earthing circuit is of a prime importance: the the surge path must have a very low stray inductance and its resistance be compliant to the standards. As a matter of example: At home, located in a quite high keraunic area, all the grid distribution cables are buried and it's a favorable situation. I have a 40y-old 220Vac protection still alive, with 3 varistors (phase-neutral, phase-earth and neutral-hearth) 400V clamping voltage @ 1mA, with a limitation of 700V for a 10Amp shock, 1200V for a 2500A shock, 1400V for 5kA or 1500V for 10kA. Response time is better than 50ns. The device has it's own earth 1m below with a straight cable, the protection is placed at the head of the distribution cabinet located 5m after the company's counter. my earth ground network resistance is well below 50 Ohms when the soil is dry. Since it's been installed, the standard voltage has been establish to 230V and I didn't see any difference. I never had any issue for 40 years. It's not the same in my neighborhood !! Then at the computer level, just because I'm paranoiac (!), i have the same scheme but with 275 V service varistors I replaced the original 250Vac by Chinese components because they were too close to the peak value of the grid voltage. The earth path is shorter than 1 meter. Read this: and for those who can read French Language. This book is very rich hence highly recommended, written both in worker language ans engineer's one ; worth to be translated with Googletrans. On 17.05.24 23:43, BuffaloJohn via
groups.io wrote:
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Re: AC Voltage
¿ªÔÆÌåÓýwe had them across the line outputs I believe on all of our computer filters . Power cord , breaker, filter MOV or maybe it was on the filter inputs . that was 30 something years back . animal On 5/17/24 9:23 PM, davesmith1800
wrote:
On Fri, May 17, 2024 at 07:32 PM, mike allen wrote: |
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Re: AC Voltage
Metal-Oxide Varistor or (MOV). ?This typical found on board of motor controller of your mini lathe or other electronics like DRO'S?
Even TVS?
?
DaveOn Fri, May 17, 2024 at 07:32 PM, mike allen wrote:
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Re: AC Voltage
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Not the electronic thyristor? |
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Re: AC Voltage
¿ªÔÆÌåÓýthat bag of 100 probably came over a ocean to get to ya . Shit that I need to be able to count on I prefer that it ca,e from the island of USA . I don't think that ya can honestly test a system which ya replaced a thyristor without a Hi-pot machine ? Or maybe ya can .? ??? That pumped storage hydro sounds like a pretty darn? good setup ! Thanks for the link . ??? animal On 5/17/24 2:01 PM, davesmith1800
wrote:
I look it up just like a power strip. One time use like a fuse.? |
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Re: AC Voltage
¿ªÔÆÌåÓýReminds me of a great Casey Stengel-ism ¡°No one goes there any more, it¡¯s too crowded¡±I was actually just reading an Washington Post article about how the California grid operators have the problem that they¡¯re getting too much power back from all the household solar that¡¯s installed. Free gift link?? There¡¯s a bunch of different technologies coming online to capture and store that excess energy, but they haven¡¯t caught up yet. Stuff like Iron-Air batteries??, and pumped storage hydro? Those iron air batteries are described as ¡¯the size of a washer-dryer ¡® combo; I wonder how much power they hold? That¡¯s a size that could conceivably work, space-wise to take a home off the grid, coupled with panels on the roof. ?
--?
Bruce Johnson The less a man knows about how sausages and laws are made, the easier it is to steal his vote and give him botulism. |
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Re: AC Voltage
Chris Albertson
¿ªÔÆÌåÓý
?Ther are no new homes for under $1M, and very hard to find for under $1.5M. ?But still they sell very fast as there are an unlimited number of buyers who can afford it or more. ?Near me by the beach, 3X to 5X higher. ?? Then that $10K upfront investment saves you $100 per month on the electric bill, that is a fast payback and then for the next 15 years you make $100/month profit. ? Most people will opt for a larger system and spend closer to 20K so most of their electric bill is covered. About what is covered? ?A surge protector is wired in PARALLEL to all house wires. ?It is not wired in series. ? So YES, it DOES protect against internally generated surges. ?In fact, placing a 200A protection in your panel box would offer some protection to neighbors who share the same utility pole transformer. ?(limited by resistance in the wires). The device clamps the rails in the box to some maximum voltage. ?It would 100% certain stop the surge from jumping across branch circuits
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Re: AC Voltage
Yes, like I wrote earlier, that is a MOV - Metal Oxide Varistor and they have either two or three leads. The ones with three leads can be used to indicate when the MOV has blown. The ones with two leads are a crapshoot if they are still good, depends how they failed. Most surge suppressors use MOVs. The biggest problem with MOVs is that the clamping voltage is really high. A MOV with an AC working voltage of 130VAC has a clamping voltage of over 350V, so you can still blow the electronics out. On Fri, May 17, 2024 at 2:21?PM davesmith1800 via <davesmith1=[email protected]> wrote: Found the name varistor. --
Buffalo John |
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Re: AC Voltage
Found the name varistor.
I was little I hope mini lathe has one or just power strip in is easier to replace. A varistor (a.k.a. voltage-dependent resistor (VDR)) is a surge protecting electronic component with an electrical resistance that varies with the applied voltage.[2] It has a nonlinear, non-ohmic current¨Cvoltage characteristic that is similar to that of a diode. Unlike a diode however, it has the same characteristic for both directions of traversing current. Traditionally, varistors were indeed constructed by connecting two rectifiers, such as the copper-oxide or germanium-oxide rectifier in antiparallel configuration. At low voltage the varistor has a high electrical resistance which decreases as the voltage is raised. Modern varistors are primarily based on sintered ceramic metal-oxide materials which exhibit directional behavior only on a microscopic scale. This type is commonly known as the metal-oxide varistor (MOV). ?
?
Metal-oxide varistor manufactured by Siemens & Halske AG. |
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Re: AC Voltage
Looks like plugs in every time to place it by a electrician.?
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20 years ago that cost $160.00 and hard wire.? At less price is coming down.? More pain? It does not protect against welders only what come from power pole.? I will stick power strip for my mini lathe.? The new home cost of solar adds $10,000 per news Dave? On Fri, May 17, 2024 at 11:41 AM, Chris Albertson wrote:
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