On Thu, 08 Sep 2011 11:23:56 -0400, Jamie
t wrote:
ehsjr wrote:
Jamie wrote:
ehsjr wrote:
NT wrote:
On Sep 2, 8:41 pm, John Fields wrote:
Snipped a lot of repetitious, self serving nonsense.
and if the relay is
designed to operate on AC with a certain RMS current in its
coil, how
can it possibly overheat if that current is DC?
With the same current it wont, with higher curren ti will. IIRC you
proposed using 174v rms,
No, I merely added a capacitor across the output of _your_ proposed
full wave rectified 120 VRMS 60Hz source (170V peak) in order to get
smoothed DC closer to the relay's must-make current.
fwliw I said use diodes, you came back with a FW BR. I dont think it
matters.
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Then show me your circuit.
Just in case you've forgotten, your suggestion was to use a 240V AC
relay using diodes and 120V mains.
---
that would be ok on your specific relay, but
not a universal solution.
???
Your proposd BR+C delivers the right i for one specific relay. For
some relays it will fry them.
---
Show me.
If you want to go get some specs of other relays, you can. This is
starting to get silly.
Worth investigating, to me. JF gave a specific relay & numbers. I
tried to find a relay to support the idea that an AC/DC relay would
be happy with DC voltage about 50% of AC rating. Can you please
provide a reference?
Meanwhile, what I did find was an ap note from Tyco entitled
"Operating DC Relays from AC and Vice-Versa" .
http://relays.te.com/appnotes/app_pdfs/13c3250.pdf
It does not agree with the DC at ~50% of AC rating idea. It uses
the example of a KR series relay coil. Their example uses a 12
volt AC relay fed by DC. The example states that the "DC voltage
cannot exceed 9.8 volts", and "should not be lower than 7.35 volts".
Thus the DC range would be ~61%(minimum) to ~81% (maximum) of the
12VAC rating.
Extrapolating, it does agree with the idea of BR+C fed by 120 for
the 240 volt relay, insofar as the DC voltage:
~146VDC min to ~194VDC max, which makes the midpoint ~170VDC.
That's very close to ~168 from the BR+C
Regarding coil ratings, I've worked with DC relays, and I've worked
with AC relays, but I haven't worked with AC/DC coil relays, so
I can't speak from experience with them, and I haven't found
anything yet specifically dealing with that, other than the
link I found to Tyco. So a specific link or links would be
most helpful.
Thanks,
Ed
You must remember that AC coil relays are wound a little different,
its not just induction here. Inter pole windings help keep the AC coil
from chattering the armature. I am sure under DC operation, this may
effect the calculations.
There are some AC coil relays that do not do this and thus the 50%
voltage for DC should come close, but then again, DC R in the coil also
plays a role in this.
Jamie
Your post contains nothing specific and does not address
my question.
I am looking for a specific link or links that shows a datasheet,
ap note, or example of a relay that NT has in mind. Do you have one?
I want specifics, like John Fields posted; the specs that NT
said you could get: "If you want to go get some specs of other
relays, you can." The specs I have been able to find so far
do not demonstrate what NT was talking about, thus my post
asking for a reference.
Ed
Don't be anal, they make relays that will do AD/DC because they have a
diode imbedded in them.
---
"Embedded."
Link?
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The voltage ratings are the same. The coil is
actually of DC type..
---
If you're saying that half-wave rectified 12VAC will cause the
armature of a relay with a 12VDC coil to close, instead of chatter,
then I'd have to ask for proof since I have empirical evidence which
refutes your assertion.
Years ago, Larkin and I had the same argument here.
He took your position and lost the argument.
---
They also have relays with shunt diodes built into
them, for those you need to insure the polarity is correct and are
strictly DC only.
---
What does that have to do with driving DC coil relays with rectified
AC, or driving AC coil relays with DC?
From my experience, those diodes are used in order to return the
coil's inductive turn-off transient to the positive supply in order to
keep E = LdI/dT from ruining a relay driver's day, and to save the
user the expense of an extra part and the PCB real estate needed for
its implementation.
---
We also deal with solenoids to operate in the same manner..
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Elaborate, please?
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Scroll down and read about AC coils, I am sure if you're looking for
some more detailed information you can find it, but this will explain
some of the differences.
http://www.ehow.com/about_6498402_di...elay-coil.html
Jamie
--
JF