Contactor/relay repair question
JohnF
destroyed the aux contacts mounted on it. Is there some way to stop
the buzzing? A replacement is nearly $3000.00 and money is very scarce
around here right now.
TIA
JohnF
Jeff Wisnia
Put a full wave rectifier in the circuit to the coil. But you might also
need a series inductor or power resistor to limit the coil current to a
reasonable level.
HTH,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Truth exists; only falsehood has to be invented."
JohnF
when we got it 10 years ago. What causes the relay to buzz anyway?
JohnF
R. O'Brian
They have accumulated dirt or rust on the faces that come together when the
contactor is energized, preventing intimate contact.
Also check the shading coil( a little copper loop inset in one face) to make
sure it is not broken or missing. That will also cause buzzing.
Randy
"JohnF" <mpi-b...@phxinternet.net> wrote in message
news:e1l2r1tnhvsfsl9fp...@4ax.com...
RoyJ
etc) that is interacting with the AC, low voltage to the windings so it
does not pull in hard, or a partially shorted winding that is not
pulling the armature in hard enough. I'd run a voltmeter on the
terminals and see what voltage you are getting. I'd also check the
current and see how it stacks up against the coil ratings.
For a $3000 unit (??), it should be fully serviceable. I'd change out
the coil.
Tom Gardner
from a jewelry hobby store and solder new blocks on the contact bars using
jeweler's silver solder sheets. Works great, lasts longer and WAY cheaper
than buying a contact set. You should splurge on a new coil and find any
other problem. Contactors should be seen but not heard.
"JohnF" <mpi-b...@phxinternet.net> wrote in message
news:e1l2r1tnhvsfsl9fp...@4ax.com...
Don Foreman
wrote:
AC relays and solenoids often have a "shading coil" to reduce buzz.
Look for something like a D made of heavy copper that surrounds only
part of the core. Sometimes it's heavy copper wire that goes thru a
hole or slot in the core. If that is missing or open (cracked),
the unit will buzz loudly. It's usually found near the "business" end
of the coil, near the armature that it moves.
How it works: the current in the coil is primarily inductive, so
about 90 out of phase with applied voltage. The current in the
shading coil is determined by transformer action from part of the
flux (since it doesn't encircle the whole core) and its (low)
resistance, so it's more in phase with applied voltage. The result
is "two phase" local magnetic flux which may fluctuate but never
goes thru zero.
If you go with DC excitation as Jeff suggests, first measure the
resistance of the coil with an ohmmeter and look at the rated AC coil
current The right average DC voltage will be the rated current times
the resistance reading. You'll probably find that it's much lower
than the rated AC voltage, so you'll probably need a dropping
transformer before your bridge rectifier.
MOP CAP
In the past I have made a new shading coil from 14 or 12 ga. copper
wire silver soldered together and forced back into the slot on the face
of the solenoid. If yours dosen't have a slot you may still be able to
put Cu wire through the holes and with a micro torch silver solder the
ends. I don't think regular solder would hold up.
Chuck P.
JohnF
them helping to stop relays from buzzing and was thinking about making
some replacements from copper wire just as you suggest. does it have
to be a continuous loop or can it be open and just crimped in the slot
of the armature?
JohnF
Don Foreman
wrote:
>The copper goodies are in there but broken. I remember something about
>them helping to stop relays from buzzing and was thinking about making
>some replacements from copper wire just as you suggest. does it have
>to be a continuous loop or can it be open and just crimped in the slot
>of the armature?
>
>JohnF
>
It has to be a closed electrical circuit, and the joint has to be
low-resistance -- welded or silversoldered. As another poster noted,
soft solder may not hold up well in that location.
Bruce L. Bergman
Gardner" <tom(nospam)@ohiobrush.com> wrote:
>"JohnF" <mpi-b...@phxinternet.net> wrote in message
>news:e1l2r1tnhvsfsl9fp...@4ax.com...
>> I have a large expensive contactor/relay that buzzes so hard it has
>> destroyed the aux contacts mounted on it. Is there some way to stop
>> the buzzing? A replacement is nearly $3000.00 and money is very scarce
>> around here right now.
Start with cleaning it all up thoroughly and lubricating per the
instructions, it may be nothing more than rust or crap keeping the
pole pieces from seating properly. Look for bent guides that are not
letting the pole pieces mate squarely against each other. Or you have
a series/parallel multi-tap coil that has one open winding.
>I started making my own contacts many years ago. I buy fine silver plate
>from a jewelry hobby store and solder new blocks on the contact bars using
>jeweler's silver solder sheets. Works great, lasts longer and WAY cheaper
>than buying a contact set. You should splurge on a new coil and find any
>other problem. Contactors should be seen but not heard.
Agreed that you can make your own - but if you sit down and honestly
figure in the labor hours needed to track down the supplies and
retread your old contact sets, that usually makes the current
production ones on the shelf cheaper. Might be time to find another
supplier with a markup more to your liking.
And I can't do it for a paying customer, because if "something goes
terribly wrong" the liability lawyers would have a field day.
If the replacement parts are totally discontinued, or they're so old
that the supplier is hand-building the replacement parts they sell
making them über-expensive, /that's/ the time to roll your own.
And when the money situation is better, buy a replacement contactor.
Preferably current production, and a bit oversized for longer life.
--<< Bruce >>--
--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.
Brian Lawson
wrote:
>I have a large expensive contactor/relay that buzzes so hard it has
Hey John,
More details about this contactor would help. Make, size, poles, coil
voltage, number and purpose/how many/NO/NC of "aux contacts".
John
Some shading coils on older contactors are made with "U" type threaded
rod with nuts. You just have to clean the thing up and it will kill the
noise. I had one a while ago that was on a big motor gen set with the
big mercury vapor tubes, for a 150 hp vertical boring mill . The
noise from the contactor could be heard through the whole plant. The
local maintenance guy couldn't believe that what I told him to do would
fix the noise but after he did it, the thing was completely quiet. I
couldn't do anything for the motor gen noise though. <G>
John
Don Young
size to fabricate a new shading coil.
Don Youngnews:hg63r1pm5glcqsre0...@4ax.com...
JohnF
"rattling" for so long the surfaces of the laminate parts are worn and
out of parallel. It appears that part of the cover that holds the
assembly together had vibrated loose some time back and let the whole
thing float around to a degree. I am going to make new shading coils
from 12ga copper wire and resurface the laminates so they will sit
flat together. I still have to get some new aux contacts/switches but
those are only about $400.00.
There is no ID except for the #'s relative to the Reliance drive part
so, at this point, I'm stuck with parts from the drive manufacturer
rather than the component manufacturer. I can find no specs in any
drawings or literature I have except that the motor is a 40HP 240vdc
and 108/150 amp listed at 850/2550 rpm.
Cover me! I'm goin' in!
JohnF
On Tue, 27 Dec 2005 14:51:50 GMT, JohnF <mpi-b...@phxinternet.net>
wrote:
>I have a large expensive contactor/relay that buzzes so hard it has
Bugs
faces. Cleanliness is next to godliness with these units. A contactor
that expensive should have replacement parts available from the mfr.
Bugs
Ken Sterling
"assembly screws" loose that held the two halves together, with the
coil between. When the screws became loose, the coil was no longer
clamped in position and it would buzz/vibrate. Simply tightening up
the assembly screws on the contactor solved the problem. Years ago,
they used to use wooden wedges on transformer coils to keep them from
buzzing. Possibly some cardboard shims, or maybe even hot melt glue
would solve your problem.
HTH
Ken.
DoN. Nichols
[ ... ]
> >In the past I have made a new shading coil from 14 or 12 ga. copper
> >wire silver soldered together and forced back into the slot on the face
> >of the solenoid. If yours dosen't have a slot you may still be able to
> >put Cu wire through the holes and with a micro torch silver solder the
> >ends. I don't think regular solder would hold up.
[ ... ]
> The copper goodies are in there but broken. I remember something about
> them helping to stop relays from buzzing and was thinking about making
> some replacements from copper wire just as you suggest. does it have
> to be a continuous loop or can it be open and just crimped in the slot
> of the armature?
It has to be a continuous loop. It has to be a very *low*
resistance shorted turn. It shifts the phase of *part* of the pole in the
solenoid, so when the main part drops to zero magnetic field during the
cycles, there is some pull from the phase-shifted part to keep it from
starting to release.
Enjoy,
DoN.
--
Email: <dnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
JohnF
THANKS for all the help.
I took the contactor apart, resurfaced the nasty, vibrated to death,
mating areas, made up new copper goodies and had them silver soldered.
Thing is quiet as a church mouse (whatever that means) now. Machine is
working again for less than 400 bucks rather than the OG $3000.00 it
was going to cost for a new contactor and aux's.
Thanks again for the help
JohnF