[CAD_CAM_EDM_DRO] Re: Remember Mr. Bill's servo lite?

What no-one seems to have mentioned, unless i missed it, is 'additional'
components into the mix.

While you MIGHT not get shocked with a variac coupled servo, if you happen
to touch your PC grounded case at the same time, you might have a very bad
experience.

In isolation, a variac or a transformer might not shock you, but all other
appliances conform to a standard, and that's why we're all alive. By
introducing a live-variac component you are upsetting the apple cart, and
introducing a 'potentially' lethal component into the equation. It would be
a good idea to label your contraption 'LIVE' just in case some innocent
bystander who does not have the same convictions as you happens to touch it
with a grounded drilling machine or whatever.

Regards
Roland

On 15 January 2012 06:39, Andy Wander <awander@...> wrote:

> **
>
>
> Hi Jeff:
>
> I appreciate the effort.
>
> But there are a couple of things that don't convince me still.
>
> For instance, to use your analogy, why is the "red" water more dangerous
> than the un-colored water?
>
> And I don't think it is correct to say beg to differ that you can't get a
> shock by touching a single wire from an isolation transformer. The chances
> are good that you will not get a shock, by completing a circuit to ground,
> but by no means absolute. The output of the "ungrounded" isolation
> transformer WILL have some potential with respect to ground-and you don't
> know what it is.
>
> Andy Wander
>
>
> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com [mailto:
> CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jeffrey T. Birt
> Sent: Saturday, January 14, 2012 11:16 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Remember Mr. Bill's servo lite?
>
> Sorry Andy, I'm really trying to be helpful but trying to explain this type
> of thing over email is not very effective.
>
> >So you don't count magnetic flux coupling as an electrical path?
>
> >It can cause current to flow, so even if you call it by a different name,
> again, what is the difference?
>
> Electrical current is the flow of electrons through a conductor (something
> with electrons that are relatively easy to break loose.) Magnetic flux is,
> well magnetic flux they are different things. Just because magnetic flux
> can
> induce a voltage (and current) flow does not mean they are the same thing.
> A
> fire will produce heat but fire and heat are not the same thing.
>
> Let's use an analogy to try and make the point more clear.
>
> Let's say you have an engine driven pump that is pumping water from a pond
> through a hose, the hose feeds into an impeller, another hose leads from
> the
> housing back to the pond. The water from the pump in turn rotates the
> impeller. This is a closed system, let's call this the 'P' side.
>
> You have a second impeller that has hoses that lead two and from a tank,
> basically it sucks water from the tank, circulates it through the impeller
> housing and discharges it back into the tank. Let's call this the 'S' side.
>
> Now let's say you mechanically couple the two impellers with a shaft. This
> means that the engine driven pump which is circulating water on the 'P'
> side
> is, by means of the mechanically coupled impellers, is also circulating
> water through the 'S' side.
>
> Now if you dump a couple of hundred gallons of red dye into the pond, the
> pond will turn red and you will have red colored water flowing through the
> 'P' side. Remember that the two side are only connected by the drive shaft
> so the 'S' side still has clear water. The two side are isolated so you
> can't get red hands by playing with things on the 'S' side.
>
> This is roughly similar to an isolation transformer. Water flowing on one
> side causes water to flow on the other side even though they are only
> coupled by a shaft, there is now water flowing directly from the pond to
> the
> tank.
>
> A Variac is like a pressure regulator. It reduces the water pressure from
> the source pump but provides no isolation. The water from the pump is the
> same water flowing through the tank.
>
> Our electrical distribution system is (earth)ground referenced. You have a
> ground rod outside your house and a wire leads from the (earth)ground rod
> to
> your electrical panel where it is connected to the (earth)ground bus (and
> the (earth)ground bus is also bonded to the neutral bus.) As you know when
> you wire your house there are three wires in the cable, 'hot' 'neutral',
> and
> '(earth)ground'. Current flows through hot and neutral while (earth)ground
> is there for safety.
>
> If you stick your finger in an electrical outlet and touch the hot terminal
> you will be shocked because your body will provide a current path to
> (earth)ground. Now let's say you plug an isolation transformer into that
> outlet and touch one of the wires on the secondary side. You won't be
> shocked because the secondary side is isolated from the primary side; there
> is no electrical connection between the primary and secondary sides. If you
> touch both wires on the secondary side you will be shocked because your
> body
> is completing a current between them.
>
> I hope that helps
>
> Jeff
>
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Andy Wander
> Sent: Saturday, January 14, 2012 8:57 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Remember Mr. Bill's servo lite?
>
> But it is NOT clear-at least not to me, Jeff. So you don't count magnetic
> flux coupling as an electrical path? It can cause current to flow, so even
> if you call it by a different name, again, what is the difference?
>
> I am not saying it is ok to use a Variac-but I am always amazed by the
> vociferous arguments of those who can't really back them up.
>
> If you can explain why it is dangerous, please do. But just saying "I can't
> make it any clearer" doesn't help me understand.
>
> Andy Wander
>
> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> ] On Behalf Of Jeffrey T. Birt
> Sent: Saturday, January 14, 2012 6:37 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Remember Mr. Bill's servo lite?
>
> There IS NO ELECTRICAL PATH from the isolated secondary to earth ground!
> That is the whole point. I do not know how much more clearly it can be
> said.
>
> Jeff Birt
>
> Soigeneris.com
>
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> ] On Behalf Of Andy Wander
> Sent: Saturday, January 14, 2012 5:04 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Remember Mr. Bill's servo lite?
>
> Again, you are only saying the "conventional" stuff, Jeff. I don't mean to
> pick on you, but can you tell me why a direct path from mains to earth is
> more dangerous than a magnetically coupled path from mains to earth?
>
> I can't see any reason why 100V, say, should be more dangerous whether it
> is
> through a transformer or directly coupled to the mains.
>
> Andy Wander
>
> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> ] On Behalf Of Jeffrey T. Birt
> Sent: Saturday, January 14, 2012 4:13 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Remember Mr. Bill's servo lite?
>
> Let's stop and consider what a transformer is and why it works. A
> transformer is two coils of wire wound around a common ferrous core. There
> is no direct electrical connection between these two coils, that is current
> (electrons) do not flow from the primary coil to the secondary coil. When
> current flows through a wire a magnetic field is produced around the wire.
> In the case of AC current, since the current is always changing the
> magnetic
> field is always changing. It just so happens that a voltage in induced on a
> wire when it is in the presence of a changing magnetic field. So here we
> have out transformer, two coils of wire that are only coupled by a magnetic
> field, thus they are isolated from one another.
>
> The secondary side of a transformer has no direct connection to the primary
> so if you measure from one side of the primary to the secondary you won't
> see a voltage there. The voltage is 'across' the secondary. A 'variac' is
> an
> autotransformer, take a look here:
> http://en.wikipedia.org/wiki/Autotransformer . As you can see there is a
> direct electrical connection between the primary and secondary sides (no
> isolation). In essence your machine is directly hooked to the mains. If
> some
> electrical wire frays and touches your machine frame (or you!) now you have
> a direct path from mains to earth, a very dangerous situation.
>
> Hope that helps
>
> Jeff Birt
>
> Soigeneris.com
>
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> ] On Behalf Of Andy Wander
> Sent: Saturday, January 14, 2012 1:18 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Remember Mr. Bill's servo lite?
>
> That;s what I don't get, and nobody seems capable of explaining it-they
> just
> say "it is".
>
> Take 2 scenarios:
>
> 1) A couple of wires plugged in to an AC outlet at 120VAC. One wire will be
> "grounded", while the other wil be at 120VAC above ground.
>
> 2) A 120VAC isolation transformer, with the primary plugged in to the same
> AC outlet, and the wires attached to the secondary.
>
> Why is #1 necessarily more dangerous? I could think up scenarios,
> especially
> if one side of the secondary is NOT grounded, where #2 would give more
> chance of a dangerous electrical shock. But let's assume one side of the
> secondary is #2 IS grounded. Why is it safer to have the isolation
> transformer?
>
> Andy Wander
>
> [Non-text portions of this message have been removed]
>
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