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From: Jon on 10 Jul 2010 22:10
This is what I'm going to do. Take a look at it and tell me what you think.
No fancy Jonathan Swift satire wanted.

http://jons-math.bravehost.com/transfer.html

look at the picture I took of my syringes

From: Dave Platt on 11 Jul 2010 01:52
In article <6bSdnRJ4UpNjuqTRnZ2dnUVZ_tmdnZ2d(a)earthlink.com>,
Jon <jon8338(a)peoplepc.com> wrote:

>This is what I'm going to do. Take a look at it and tell me what you think.

I think you could have serious problems under certain sorts of fault
conditions you haven't considered.

For example: think of what will happen if a fault on the service side
entirely knocks out the "right" phase of the incoming service, and the
"left" side suffers a partial brownout (or blinks off momentarily and
then comes back on, but perhaps not all the way).

This would cause your "A" relay to open and remain open (it won't pull
in with less than half of the usual voltage across it, or none at all
if the right side of the service failed "open"), and will fool
your entire system into "thinking" that the service voltage is
completely gone... but the left side will still be at least partially
live. If you then start up the generator without opening the transfer
switch, something will go boom for certain. Your fault-detect circuit
won't catch this, since there's only partial voltage across the "A"
coil in this case (not enough to close A's contacts) and so L won't
operate.

Since this incarnation of your circuit seems to be depending on the
fault-detection circuit to determine whether you accidentally didn't
open the disconnect before starting the generator, you've got a
problem. The whole idea of using a fault detector to discover the
mistake (after the fact) rather than preventing it (by using a listed
transfer switch with the right sorts of purely mechanical interlocks),
is a really bad idea.

Even if the fault detector *does* trip, it'll take time to open the C
relay... and this is a few milliseconds during which your generator
could be short-circuited right across the service power. If you're
especially unlucky, the C relay's contacts could arc and weld shut,
leaving your generator stuck on the line indefinitely.

The whole reason the codes specify the use of a mechanically-
interlocked transfer switch, rather than a complex set of logic (relay
or otherwise), is that a mechanical interlock works even in the face
of weird fault conditions (power bouncing on and off repeatedly,
voltages being low or high, etc.). It's immune to these sorts of things.
Your approach is not, and cannot be made so... the more relays and
"logic" you throw at it, the more vulnerable it is to strange
interactions of voltage and timing.

That's why people don't use this approach... it's fundamentally unsafe.

Please, DO NOT DEPLOY this thing you're working on.

>No fancy Jonathan Swift satire wanted.

By the way, your recent few versions of the page don't render properly
in Mozilla Firefox... the pictures don't show up.

http://www.totalvalidator.com/ says that there are a total of 17
errors in your page, 9 of which involve improper HTML.

--
Dave Platt <dplatt(a)radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
From: m II on 11 Jul 2010 04:37
Dave Platt wrote:
> In article <6bSdnRJ4UpNjuqTRnZ2dnUVZ_tmdnZ2d(a)earthlink.com>,
> Jon <jon8338(a)peoplepc.com> wrote:
>
>> This is what I'm going to do. Take a look at it and tell me what you think.
>
> I think you could have serious problems under certain sorts of fault
> conditions you haven't considered.


There are a couple of other things. WE are NOT giving him advice on how
to do his electrical abomination. You and I are discussing a
hypothetical case that does NOT apply to ANY venture Mister Giffen may
undertake now or at anytime in the future.


a) You can NOT connect stuff to the hot side of the disconnect switch.
EVERYTHING has to be disconnected when that switch is open. Coil A and
everything associated with it is BAD.

b) In many residential cases, the main breaker is also the disconnect,
so this setup also bypasses the safety mechanism.

b) What happens if a coil fails during use? A disaster. Failure must
cause a safe *stop*, NOT activation.

c) In normal AC use, if the disconnect switch is closed, coils A and B
are on. That makes the latching relay turn ON, showing an error.

d) A latching relay here makes no sense. You want it to keep a fault
signal? OK, but don't use it to work a contact that does something else,
besides, as soon as A or B open it gets reset anyway, because it's wired
wrong.

d) A reset switch should be of the NC type and in series with a holding
contact.

e) There are no overcurrent devices protecting any of his control circuitry.

d) Everything you said...and probably something I've overlooked.


Mister Giffen had told the world that God had designed the ancestor of
this thing. That circuit was even worse than this one. Is God
incompetent or did Jon lie? Perhaps God wanted KILL Jon and we are
inadvertently preventing HIM from carrying out his Divine Will.



mike
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