On Sep 12, 11:27*am, Jamie
t wrote:
The Ghost In The Machine wrote:



On Sep 11, 9:05 pm, Jamie
t wrote:

John S wrote:

On 9/9/2011 6:53 PM, Jamie wrote:

John S wrote:

On 9/9/2011 6:30 PM, Jamie wrote:

ehsjr wrote:

I don't know how to make it clear enough for you to understand.
While I do appreciate your attempt to help, I must say it misses
the point.

I want a *specific* link to an *AC/DC* relay of the type *NT*
had in mind, or to an ap note or reference that discusses a relay
coil that is rated for *both* AC and DC as he indicated.

Do you have a link to what NT was talking about? Here's what
he said:
"The various ones I've seen that have coil 2 ratings, one for ac one
for dc, have consistently had the dc coil rating be half the ac
voltage rating."

I _do not_ need generalizations, hand waving and condescending
responses. You mentioned a relay that will "do" DC because it
has an imbedded (sic) diode and say "The voltage ratings are the
same." That is *NOT* what NT said. He talks about the dc
coil rating being half the ac rating.

Ed

Is this what you're looking for ?

http://relays.te.com/appnotes/app_pdfs/13c3250.pdf

Geeeez. I posted that link in my _first_ post in the thread, and
you replied to that post. I guess you either didn't read the post
properly, or didn't understand it. The ap note does not agree with
the DC at ~50% of AC rating idea - details are given in that post.

Sorry, I didn't see that.

It explains operating AC coils on DC and AC coils using
the internal DIODES for shading rings design.

No, that wasn't a hack as far as the diodes goes, that is a practical
design in a family of relays, We use large contactors with the dual
coil and diodes in them. You don't see this from the out side world but
they are incased in the encapsulation. Those particular types can have
DC going directly to them. It's just the way they are with obvious
reasons.

Yup. To operate an AC relay on DC, (the Tyco ap note says
doing so is impractical, but that you can do it in an
emergency) you should install a residual and you must lower
the voltage below the AC rating. An AC rated coil needs DC
in excess of 61% of the ac rating on the minimum side, and
less than 82% of the ac rating on the maximum side, per the
example given in the ap note.

The app note is pointing equivalent power dissipation, as you
know relays will pull in at a lower current So I don't see a problem
here.

Why don't you put a few AC types on the bench and test them yourself?

I think you'd be surprised in what you find. Lab testing tells a lot
about what you can do.

The only problem I have found with this practice of using AC on DC is
that some AC units use material that has a high hysteresis and the
AC will help keep this down. They do this in cases where they don't use
the dual coil system. In DC operation, I've seen it over magnetize the
core and cause a little slow release on the contacts. But that may not
be such a big deal in most cases.

Have a good day.

Jamie

I have an Essex contactor which was removed from my old A/C outside
unit. It has a 24VAC 50/60 Hz coil. I can make some measurements on it
if anyone is interested.

John S

If you have IR gun/camera, you should also do some comparisons.

Jamie

BTW, Jamie, if by IR gun/camera you are interested in coil temperature
rise, that can be done using the copper resistance vs temperature rise
method.

And, which comparisons are you referring to?

John S

*I have IR equipment, I just thought that most people that work in this
field would at least have a small hand held unit. *When doing quick
checks between induction and DC R it's a quick and dirty way to
determine the operating range of AC coil in a DC environment.

* * Most AC coil design i've seen try to balance between DC R and
induction, for obvious reasons.

* * We use one of the Humphrey solenoid valve series at work that employs
a single DIODE in series to operate the coil from the 120AC control
voltage in many different applications.

* * *I suppose it's possible those units actually have a 240 AC coil in
them and that is done for 120 volt operation. Or say that it could be
done to help keep the valve from sticking, thus allowing it to buzz
just a little how ever, these unit runs perfectly quiet and if they're
buzzing I can't hear or feel it? Depends on the hysteresis in the core I
guess.

Have a good day.

*Jamie

YES JAMIE TAKE YOUR HUMPHREYS BABY PILLS...
YOU ARE HYSTERICAL...BOOWAHAHAHAHA!

THE HYSTERISIS CURVE IS A CHARACTERISTIC OF A WAVE FORM., NOT INSIDE
THE CORE BUT *THE INPUT/OUTPUT SIGNAL.......

TRY AND HAVE A NICE WEEK
PATTYCAKE
TGITM

BOOWAHAHAHAHAHAHA !

Goes to show what you know about induction and construction of such things.

* Buzz off..

Jamie

PHASE OFF CREEP ..
I AINT NOBODY FOR YOU OR ANY OF YOU SUBLIMIE SLIME TROLLS TO BE
****ING WITH.

YOU DONT KNOW **** ABOUT BEING PEOFESSIONAL AND POLITE, ALL YOU DO IS
SPOUT OFF THEORETICAL CRAP AND INSULT OTHERS.

THE GRAVE AND THE PITS OF HELL WILL BE YOUR REWARD.

PATECUM