[Amps] RE: Amps digest, Vol 1 #20 - 6 msgs

jljarvis jljarvis@abs.adelphia.net
Fri, 8 Mar 2002 15:19:57 -0500


220V GFCI breakers are available from most electrical supply stores.
You may also find them at Home Depot or Lowes, for some types of
panels.  There are packaging differences which make mixing vendors
dicey.   You should also expect to pay through the nose for these.

I have one on an outdoor jacuzzi....50 amps cost me $100!

n2ea


-----Original Message-----
From: amps-admin@contesting.com [mailto:amps-admin@contesting.com]On
Behalf Of amps-request@contesting.com
Sent: Friday, March 08, 2002 3:09 PM
To: amps@contesting.com
Subject: Amps digest, Vol 1 #20 - 6 msgs


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Today's Topics:

   1. Re: Source for 220V cords (Bill Coleman)
   2. Re: Source for 220V cords (Bill Coleman)
   3. RE: Source for 220V cords (PAUL HEWITT)
   4. RE: Source for 220V cords (PAUL HEWITT)
   5. Re: Source for 220V cords --Thanks (Bill Coleman)
   6. Re: Glitch resistors (Ian White, G3SEK)

--__--__--

Message: 1
From: "Bill Coleman" <n2bc@stny.rr.com>
To: "Gary Schafer" <garyschafer@attbi.com>
Cc: "Richard" <2@mail.vcnet.com>, "Steve Katz" <stevek@jmr.com>,
   <RMead100@aol.com>, "AMPS" <amps@contesting.com>
Subject: Re: [Amps] Source for 220V cords
Date: Fri, 8 Mar 2002 14:20:00 -0500

Two pole GFCI's not hard to find at all.  Probably best to go to an
electrical supply rather than a DIY home store.  Of course the type of panel
makes a difference too.  I found out the manufacturer of my original panel
had gone out of the home business - then I found out why (something about
breakers not tripping...).   An entire new panel resulted.
~~~~~~~~~~~~~~~~
Bill Coleman    N2BC
http://home.stny.rr.com/n2bc
----- Original Message -----
From: "Gary Schafer" <garyschafer@attbi.com>
To: "Bill Coleman" <n2bc@stny.rr.com>
Cc: "Richard" <2@mail.vcnet.com>; "Steve Katz" <stevek@jmr.com>;
<RMead100@aol.com>; "AMPS" <amps@contesting.com>
Sent: Friday, March 08, 2002 11:22 AM
Subject: Re: [Amps] Source for 220V cords


> Yes Bill, a simple rule is "ground should never carry any current".
>
> One note about ground fault breakers, if you are gong to install them on a
220
> volt line they need to be double pole type just like any other 220
breaker. They
> are kind of hard to find I think.
>
> 73
> Gary  K4FMX
>
>
> Bill Coleman wrote:
>
> > Ground and Neutral are the same in the MAIN breaker box - not
necessarily in
> > all breaker boxes...  A branch circuit (probably quite common for
> > post-construction install of 240V in our shacks) must have the neutral
and
> > ground separated.  You should not wire up a device anywhere which
requires
> > neutral (i.e. the neutral is carrying current) to the ground instead of
> > neutral.
> >
> > A slight digression:  Ground-fault and arc-fault breakers rely on
separate
> > ground and neutral - or stated differently, they rely on current NOT
being
> > returned on the ground.  I would recommend that our shack and workshop
> > branch circuits all be fed by a ground-fault breaker.  I feel better
knowing
> > that a milliamp difference in the load between hot and neutral  will
likely
> > trip the breaker rather than a 40A overload running up my arm and out to
the
> > frame of a piece of radio junque.
> > ~~~~~~~~~~~~~~~~
> > Bill Coleman    N2BC
> > http://home.stny.rr.com/n2bc
> > ----- Original Message -----
> > From: "Richard" <2@mail.vcnet.com>
> > To: "Gary Schafer" <garyschafer@attbi.com>
> > Cc: "Steve Katz" <stevek@jmr.com>; <RMead100@aol.com>; "AMPS"
> > <amps@contesting.com>
> > Sent: Friday, March 08, 2002 7:02 AM
> > Subject: Re: [Amps] Source for 220V cords
> >
> > >
> > >
> > >Richard wrote:
> > >
> > >> >A window air conditioner cord is what you want. They have a molded
plug
> > on
> > >> >them,
> > >> >although they are not usually all that long. Can be found in Home
Depot,
> > >> >Lows or
> > >> >probably most larger hardware stores.
> > >> >
> > >> >By the way I think that a 15 amp 220 plug has one blade turned 90
> > degrees
> > >and
> > >> >the 20 amp plug has both blades 90 degrees from what a standard 120
volt
> > >plug
> > >> >would be.
> > >> >These are all 3 wire plugs. 2 hot and ground. No neutral connection.
I
> > think
> > >> >that the SB220 will run without the neutral on 220 vac.
> > >> >
> > >> Do this and the chassis is not returned to mains neutral/gnd at the
> > >> breaker box.
> > >>
> > >> -  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> > >> www.vcnet.com/measures.
> > >> end
> > >
> > >I am not sure about the SB220 but the SB200 does not require a neutral
> > connection
> > >on 220 volts. The fan is the only 120 volt item in the amp. It gets
> > connected
> > from
> > >one hot side to the center connection of the transformer primary. This
acts
> > as an
> > >auto transformer to give 120 volts for the fan.
> >
> > ?  True. Gary.   Also, green/ground and white/neutral are the same point
> > in the breaker box.
> >
> > >The chassis ground still goes to
> > >the green wire (center pin) as it did with the 120 volt connection. No
> > neutral
> > >connection is needed as there is no 120 volts as far as the line is
> > >concerned.
> >
> > -  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> > www.vcnet.com/measures.
> > end
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>



--__--__--

Message: 2
From: "Bill Coleman" <n2bc@stny.rr.com>
To: "Gary Schafer" <garyschafer@attbi.com>,
   "Phil Clements" <philk5pc@tyler.net>
Cc: "Richard" <2@mail.vcnet.com>, "Steve Katz" <stevek@jmr.com>,
   <RMead100@aol.com>, "AMPS" <amps@contesting.com>
Subject: Re: [Amps] Source for 220V cords
Date: Fri, 8 Mar 2002 14:30:56 -0500

I agree with Gary about branch circuits - the ground and neutral must be
maintained separate & the neutral connection bar is isolated from the branch
circuit box chassis.

The discussion about 3-wire vs 4-wire triggered another code item I
discovered.  I had planned to run a couple 240V feeds with 4-wire but not
use the neutral.  Code says "no unused conductors".  Rats, so much for
planning ahead.

Consult the codes, consult/hire an electrician if not comfortable.  I'm
lucky that the town building inspector is a friend and neighbor, he's helped
out on my tower (a looong story) and electrical improvements.  Helped keep
me out of trouble!
~~~~~~~~~~~~~~~~
Bill Coleman    N2BC
http://home.stny.rr.com/n2bc
----- Original Message -----
From: "Gary Schafer" <garyschafer@attbi.com>
To: "Phil Clements" <philk5pc@tyler.net>
Cc: "Bill Coleman" <n2bc@stny.rr.com>; "Richard" <2@mail.vcnet.com>; "Steve
Katz" <stevek@jmr.com>; <RMead100@aol.com>; "AMPS" <amps@contesting.com>
Sent: Friday, March 08, 2002 1:20 PM
Subject: Re: [Amps] Source for 220V cords


>
>
> Phil Clements wrote:
>
> > > > Ground and Neutral are the same in the MAIN breaker box - not
necessarily in
> > > > all breaker boxes...  A branch circuit (probably quite common for
> > > > post-construction install of 240V in our shacks) must have the
neutral and
> > > > ground separated.  You should not wire up a device anywhere which
requires
> > > > neutral (i.e. the neutral is carrying current) to the ground instead
of
> > > > neutral.
> >
> > Right on, Bill!
> > This subject comes up several times per year, so let me try to draw a
mental
> > picture for those who are planning 240 volt service into the shack.
> >
> > The location where the power lines come into the building and terminate
in the
> > main breaker box is called the "service entrance" by those in the trade.
As
> > close as possible to this breaker box, ground rod(s) are installed. The
ground
> > rod should be 8 feet or longer. Do not try to save a few bucks by using
cheap
> > rods; get a good one like the power companies use. As we will see later,
this
> > rod plays an important part in the system. It is referred to in the
trade as the
> > "service entrance ground." A good quality wire is run from the breaker
box
> > ground bus bar ( a long bar with many holes and set screws for
installing wires)
> > to the ground rod. As Bill stated, the difference between a main service
panel
> > and a sub-panel is that on the main panel the ground bus bar and the
neutral
> > bus bar (which is insulated from the box) are strapped together by a
jumper
> > wire. When running romex throughout the building, the white wires go to
the
> > neutral bus bar, and the bare wires go to the ground bus bar. When
installing
> > a sub-panel down-line, the ground (un-insulated) bus bar in the sub
panel
> > is unused. Both the white and bare romex wires are hooked to the neutral
bus
> > bar.
>
> This is wrong. The neutral and ground are NEVER tied together except at
the MAIN
> breaker panel.
> This is even true when in some installations the main house breaker is
outside and
> the distribution panel with all the branch circuit breakers is mounted
inside. The
> ground and neutral are NOT connected together even in this panel. They are
only
> connected together at the outside main circuit breaker.
>
>
> >
> >
> > To get 240 volts, a dual breaker is installed in the sub-panel. The
black and
> > white wires on the romex go to the terminals on the dual breaker, and
the
> > bare wire hooks to the neutral bus bar. The 240 volt plug and socket in
the
> > shack are wired so that the black white and green wires coming from the
> > amp hook to the black white and bare wires coming from the sub-panel.
>
> This is wrong also. First you never hook a white wire to a hot 220
terminal. White
> ALWAYS goes to the neutral line. If you are running 220 you need a 4 wire
line. They
> have RED, Black, White and a bare ground wire. Again the only place the
neutral and
> bare ground wires are tied together is in the main breaker panel. The red
and black
> wires are the two hot lines from either side of the 220.
>
> The exception to this is sometimes window air conditioners have a 220 line
to them.
> Or a pool or well pump that is only 220 volts. In this case they have no
need for a
> neutral as they only operate on 220 volts. A three wire line can be used.
Sometimes
> a regular romex (black, white and ground wires) is used. The black goes to
one side
> of the 220 and the white goes to the other side of the 220.  BUT it is
marked with
> RED tape at each end to identify it as a hot line. The bare wire is
connected to the
> ground buss in the panel and the outlet end of the line goes to the ground
pin.
> There is no neutral involved in this circuit.
>
> If a neutral is needed a 4 wire line and 4 wire outlet must be used.
>
>
>
> >
> >
> > In an ideal installation, the power, phone, and TV antenna grounds
should all
> > hook to the service entrance ground, and enter the building at the same
place.
> > Another "RF Ground" rod(s) should be installed as close as possible to
the
> > operating
> > position in the station, and solid strap, tubing, or wire run from the
radio,
> > amp,
> > tuner and accessories to this rod. I also add several buried radials to
this rod
> > to assist in keeping RF off all the equipment chassis.
> >
> > (((73)))
> > Phil, K5PC
>
> 73
> Gary  K4FMX
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>



--__--__--

Message: 3
Reply-To: <wd7s@att.net>
From: "PAUL HEWITT" <wd7s@att.net>
To: "Gary Schafer" <garyschafer@attbi.com>,
   "Phil Clements" <philk5pc@tyler.net>
Cc: "Bill Coleman" <n2bc@stny.rr.com>, "Richard" <2@mail.vcnet.com>,
   "Steve Katz" <stevek@jmr.com>, <RMead100@aol.com>,
   "AMPS" <amps@contesting.com>
Subject: RE: [Amps] Source for 220V cords
Date: Fri, 8 Mar 2002 11:40:04 -0800




> -----Original Message-----
> From:
> amps-admin@contesting.com
> [mailto:amps-admin@contesting.com]On
> Behalf Of Gary Schafer
> Sent: Friday, March 08, 2002 10:20 AM
> To: Phil Clements
> Cc: Bill Coleman; Richard;
> Steve Katz; RMead100@aol.com; AMPS
> Subject: Re: [Amps] Source
> for 220V cords
>
>
>
>
> Phil Clements wrote:
>
> > > > Ground and Neutral are
> the same in the MAIN breaker
> box - not necessarily in
> > > > all breaker boxes...  A
> branch circuit (probably
> quite common for
> > > > post-construction
> install of 240V in our
> shacks) must have the neutral and
> > > > ground separated.  You
> should not wire up a device
> anywhere which requires
> > > > neutral (i.e. the
> neutral is carrying current)
> to the ground instead of
> > > > neutral.
> >
> > Right on, Bill!
> > This subject comes up
> several times per year, so
> let me try to draw a mental
> > picture for those who are
> planning 240 volt service
> into the shack.
> >
> > The location where the
> power lines come into the
> building and terminate in the
> > main breaker box is called
> the "service entrance" by
> those in the trade. As
> > close as possible to this
> breaker box, ground rod(s)
> are installed. The ground
> > rod should be 8 feet or
> longer. Do not try to save a
> few bucks by using cheap
> > rods; get a good one like
> the power companies use. As
> we will see later, this
> > rod plays an important part
> in the system. It is referred
> to in the trade as the
> > "service entrance ground."
> A good quality wire is run
> from the breaker box
> > ground bus bar ( a long bar
> with many holes and set
> screws for installing wires)
> > to the ground rod. As Bill
> stated, the difference
> between a main service panel
> > and a sub-panel is that on
> the main panel the ground bus
> bar and the neutral
> > bus bar (which is insulated
> from the box) are strapped
> together by a jumper
> > wire. When running romex
> throughout the building, the
> white wires go to the
> > neutral bus bar, and the
> bare wires go to the ground
> bus bar. When installing
> > a sub-panel down-line, the
> ground (un-insulated) bus bar
> in the sub panel
> > is unused. Both the white
> and bare romex wires are
> hooked to the neutral bus
> > bar.
>
> This is wrong. The neutral
> and ground are NEVER tied
> together except at the MAIN
> breaker panel.
> This is even true when in
> some installations the main
> house breaker is outside and
> the distribution panel with
> all the branch circuit
> breakers is mounted inside. The
> ground and neutral are NOT
> connected together even in
> this panel. They are only
> connected together at the
> outside main circuit breaker.
>
>
> >
> >
> > To get 240 volts, a dual
> breaker is installed in the
> sub-panel. The black and
> > white wires on the romex go
> to the terminals on the dual
> breaker, and the
> > bare wire hooks to the
> neutral bus bar. The 240 volt
> plug and socket in the
> > shack are wired so that the
> black white and green wires
> coming from the
> > amp hook to the black white
> and bare wires coming from
> the sub-panel.
>
> This is wrong also. First you
> never hook a white wire to a
> hot 220 terminal. White
> ALWAYS goes to the neutral
> line. If you are running 220
> you need a 4 wire line. They
> have RED, Black, White and a
> bare ground wire. Again the
> only place the neutral and
> bare ground wires are tied
> together is in the main
> breaker panel. The red and black
> wires are the two hot lines
> from either side of the 220.
>
> The exception to this is
> sometimes window air
> conditioners have a 220 line to them.
> Or a pool or well pump that
> is only 220 volts. In this
> case they have no need for a
> neutral as they only operate
> on 220 volts. A three wire
> line can be used. Sometimes
> a regular romex (black, white
> and ground wires) is used.
> The black goes to one side
> of the 220 and the white goes
> to the other side of the 220.
>  BUT it is marked with
> RED tape at each end to
> identify it as a hot line.
> The bare wire is connected to the
> ground buss in the panel and
> the outlet end of the line
> goes to the ground pin.
> There is no neutral involved
> in this circuit.
>
> If a neutral is needed a 4
> wire line and 4 wire outlet
> must be used.
>
>
>
> >
> >
> > In an ideal installation,
> the power, phone, and TV
> antenna grounds should all
> > hook to the service
> entrance ground, and enter
> the building at the same place.
> > Another "RF Ground" rod(s)
> should be installed as close
> as possible to the
> > operating
> > position in the station,
> and solid strap, tubing, or
> wire run from the radio,
> > amp,
> > tuner and accessories to
> this rod. I also add several
> buried radials to this rod
> > to assist in keeping RF off
> all the equipment chassis.
> >
> > (((73)))
> > Phil, K5PC
>
> 73
> Gary  K4FMX

A couple of missed points;  The ground
rod is no longer legal for most states
in NEW construction.  A UFER ground is
now required, rebar embedded in the
foundation wall or slab.  Be sure to
check with local building codes
officials.  Also, some localities
require MORE than one ground rod when
replacing an old one, soil conductivity
is now an issue.

If the sub panel is installed on a
DETACHED building (backyard shack) a
ground rod (or Ufer) may be required at
that panel as it a service entrance for
that building.  Again check with local
officials
Paul

PAUL HEWITT
WD7S PRODUCTIONS
QRO HOMEBREW COMPONENTS
http://wd7s.home.att.net


--__--__--

Message: 4
Reply-To: <wd7s@att.net>
From: "PAUL HEWITT" <wd7s@att.net>
To: "Gary Schafer" <garyschafer@attbi.com>,
   "Phil Clements" <philk5pc@tyler.net>
Cc: "Bill Coleman" <n2bc@stny.rr.com>, "Richard" <2@mail.vcnet.com>,
   "Steve Katz" <stevek@jmr.com>, <RMead100@aol.com>,
   "AMPS" <amps@contesting.com>
Subject: RE: [Amps] Source for 220V cords
Date: Fri, 8 Mar 2002 11:40:46 -0800




> -----Original Message-----
> From:
> amps-admin@contesting.com
> [mailto:amps-admin@contesting.com]On
> Behalf Of Gary Schafer
> Sent: Friday, March 08, 2002 10:20 AM
> To: Phil Clements
> Cc: Bill Coleman; Richard;
> Steve Katz; RMead100@aol.com; AMPS
> Subject: Re: [Amps] Source
> for 220V cords
>
>
>
>
> Phil Clements wrote:
>
> > > > Ground and Neutral are
> the same in the MAIN breaker
> box - not necessarily in
> > > > all breaker boxes...  A
> branch circuit (probably
> quite common for
> > > > post-construction
> install of 240V in our
> shacks) must have the neutral and
> > > > ground separated.  You
> should not wire up a device
> anywhere which requires
> > > > neutral (i.e. the
> neutral is carrying current)
> to the ground instead of
> > > > neutral.
> >
> > Right on, Bill!
> > This subject comes up
> several times per year, so
> let me try to draw a mental
> > picture for those who are
> planning 240 volt service
> into the shack.
> >
> > The location where the
> power lines come into the
> building and terminate in the
> > main breaker box is called
> the "service entrance" by
> those in the trade. As
> > close as possible to this
> breaker box, ground rod(s)
> are installed. The ground
> > rod should be 8 feet or
> longer. Do not try to save a
> few bucks by using cheap
> > rods; get a good one like
> the power companies use. As
> we will see later, this
> > rod plays an important part
> in the system. It is referred
> to in the trade as the
> > "service entrance ground."
> A good quality wire is run
> from the breaker box
> > ground bus bar ( a long bar
> with many holes and set
> screws for installing wires)
> > to the ground rod. As Bill
> stated, the difference
> between a main service panel
> > and a sub-panel is that on
> the main panel the ground bus
> bar and the neutral
> > bus bar (which is insulated
> from the box) are strapped
> together by a jumper
> > wire. When running romex
> throughout the building, the
> white wires go to the
> > neutral bus bar, and the
> bare wires go to the ground
> bus bar. When installing
> > a sub-panel down-line, the
> ground (un-insulated) bus bar
> in the sub panel
> > is unused. Both the white
> and bare romex wires are
> hooked to the neutral bus
> > bar.
>
> This is wrong. The neutral
> and ground are NEVER tied
> together except at the MAIN
> breaker panel.
> This is even true when in
> some installations the main
> house breaker is outside and
> the distribution panel with
> all the branch circuit
> breakers is mounted inside. The
> ground and neutral are NOT
> connected together even in
> this panel. They are only
> connected together at the
> outside main circuit breaker.
>
>
> >
> >
> > To get 240 volts, a dual
> breaker is installed in the
> sub-panel. The black and
> > white wires on the romex go
> to the terminals on the dual
> breaker, and the
> > bare wire hooks to the
> neutral bus bar. The 240 volt
> plug and socket in the
> > shack are wired so that the
> black white and green wires
> coming from the
> > amp hook to the black white
> and bare wires coming from
> the sub-panel.
>
> This is wrong also. First you
> never hook a white wire to a
> hot 220 terminal. White
> ALWAYS goes to the neutral
> line. If you are running 220
> you need a 4 wire line. They
> have RED, Black, White and a
> bare ground wire. Again the
> only place the neutral and
> bare ground wires are tied
> together is in the main
> breaker panel. The red and black
> wires are the two hot lines
> from either side of the 220.
>
> The exception to this is
> sometimes window air
> conditioners have a 220 line to them.
> Or a pool or well pump that
> is only 220 volts. In this
> case they have no need for a
> neutral as they only operate
> on 220 volts. A three wire
> line can be used. Sometimes
> a regular romex (black, white
> and ground wires) is used.
> The black goes to one side
> of the 220 and the white goes
> to the other side of the 220.
>  BUT it is marked with
> RED tape at each end to
> identify it as a hot line.
> The bare wire is connected to the
> ground buss in the panel and
> the outlet end of the line
> goes to the ground pin.
> There is no neutral involved
> in this circuit.
>
> If a neutral is needed a 4
> wire line and 4 wire outlet
> must be used.
>
>
>
> >
> >
> > In an ideal installation,
> the power, phone, and TV
> antenna grounds should all
> > hook to the service
> entrance ground, and enter
> the building at the same place.
> > Another "RF Ground" rod(s)
> should be installed as close
> as possible to the
> > operating
> > position in the station,
> and solid strap, tubing, or
> wire run from the radio,
> > amp,
> > tuner and accessories to
> this rod. I also add several
> buried radials to this rod
> > to assist in keeping RF off
> all the equipment chassis.
> >
> > (((73)))
> > Phil, K5PC
>
> 73
> Gary  K4FMX

A couple of missed points;  The ground
rod is no longer legal for most states
in NEW construction.  A UFER ground is
now required, rebar embedded in the
foundation wall or slab.  Be sure to
check with local building codes
officials.  Also, some localities
require MORE than one ground rod when
replacing an old one, soil conductivity
is now an issue.

If the sub panel is installed on a
DETACHED building (backyard shack) a
ground rod (or Ufer) may be required at
that panel as it a service entrance for
that building.  Again check with local
officials
Paul

PAUL HEWITT
WD7S PRODUCTIONS
QRO HOMEBREW COMPONENTS
http://wd7s.home.att.net


--__--__--

Message: 5
From: "Bill Coleman" <n2bc@stny.rr.com>
To: "Richard" <2@mail.vcnet.com>, <RMead100@aol.com>,
   " AMPS" <amps@contesting.com>
Subject: Re: [Amps] Source for 220V cords --Thanks
Date: Fri, 8 Mar 2002 14:46:06 -0500

Interesting... I've never had a problem with RF bothering a GFCI.  My KW AM
broadcast transmitter (in the garage) is on a 30A two-pole GFCI about 20'
away from the panel with other GFCIs. The old RCA gets into my phones, the
TV, the stereo - but never bothered it's GFCI nor any of the others. All the
circuits in the shack and workshop (and kitchen and baths and outdoors) are
GFCIs - never been bothered by RF.

Somebody mentioned they are expensive... guess you have to define expensive.
Sure they are $40 when a vanilla breaker is $4.  $36 seems like cheap
one-shot insurance to me.
~~~~~~~~~~~~~~~~
Bill Coleman    N2BC
http://home.stny.rr.com/n2bc
----- Original Message -----
From: "Richard" <2@mail.vcnet.com>
To: <RMead100@aol.com>; " AMPS" <amps@contesting.com>
Sent: Friday, March 08, 2002 12:40 PM
Subject: Re: [Amps] Source for 220V cords --Thanks




>
>Wow,
>
>Thanks to all the responders.  Actually, I haven't installed the 220
circuit
>yet, but I will look into how it should be wired relative to having all
four
>wires in to the box. Also hadn't thought about how the fan worked, but will
>take a look at that circuit too.
>
>The GFCI breaker suggestion seems to make a great deal of sense.
>
?  ... and they usually help to reduce TVI too because when the amplifier
makes mo' RF, the 240v switches off.
>
cheerz, Randy

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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Message: 6
Date: Fri, 8 Mar 2002 18:38:49 +0000
To: amps@contesting.com
From: "Ian White, G3SEK" <G3SEK@ifwtech.com>
Reply-To: "Ian White, G3SEK" <g3sek@ifwtech.com>
Subject: Re: [Amps] Glitch resistors

wb4mnf wrote:
> Not needed with RL filter. Only RC filter. Right?
>

Do you mean:
"Not needed with LC filter, only C filter. Right?"

If so, the answer's  No - wrong. They both have a C on the output, and 
there is more than enough energy stored in a typical C to damage a tube, 
if all of that stored energy gets dumped into the tube (eg due to an 
internal arc).

For example, 30uF charged up to 3kV stores 135 joules of energy (E = 0.5 
* C* V^2). Eimac's limit for energy dumped into tubes up to 1500W anode 
dissipation is only 4 joules [1] - so you really do need to take some 
precautions.

The purpose of the glitch resistor is to absorb the energy of a current 
surge, so that the tube doesn't have to. The voltage drop across an arc 
is probably only about 50V [1] so that in an arc from 3kV, 2950V appears 
across the glitch resistor and only 50V across the tube. This means that 
only 1.7% of the total energy goes into the tube - all the rest goes 
into the resistor.

For 135J stored in the capacitor, this would mean that only 2.25J gets 
dumped into the tube, which is comfortably less than the 4J limit.

But the mains power is still switched on, and still pouring energy in! 
This means that as well as the glitch resistor, you need a *fast* way of 
interrupting the mains supply.

A fast, low-rated mains fuse or breaker is generally good enough (but it 
requires a step-start in order to be able to switch the thing on without 
blowing the fuse or tripping the breaker).

Better is a fast mains relay, powered by a circuit that senses excessive 
anode current.

Best of all is a circuit that senses excessive anode current, switches 
off the mains, and at the same time fires a thyristor "crowbar" that 
shorts the B+ supply to the tube. This means that almost all the stored 
energy in the capacitor gets dumped into the glitch resistor. A good 
example is at:
http://www.qsl.net/oe5jfl/flashover.htm

It's the usual deal - you can get adequate protection very simply 
(glitch resistor and fuse) *if* you select the right components. Better 
protection is possible, but also more complicated. As ever, it's your 
choice.

[1] Eimac Application Bulletin #17, 'Fault Protection'

I'm keeping this whole thread (thanks also for the e-mails about sources 
of glitch resistors) and by the end of this should have enough material 
to throw together that promised "flashover FAQ".


-- 
73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                           'In Practice' columnist for RadCom (RSGB)
                            http://www.ifwtech.com/g3sek


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