Buzzing relays

DrivingMissLazy · July 22, 2008, 06:43:31 PM

It is my recollection that inserting a diode in the 120 volt feed to an AC relay is that it will drop the voltage to somewhere in the 65 volt range.

I used to do this in some of the equipment I manufactured. I would use the full 120 volts to energize the relay or solenoid and then insert a diode in the circuit to hold the relay energized. This significantly increased the life span of the unit. After the units were up to speed I also transferred all the operational control voltage from the dirty utility power to the clean output power of the power conditioner.

Richard

gumpy · July 23, 2008, 04:51:18 AM

Well, I tried the diode trick. I put one of the 1N4004 diodes in the ground side of the coil control line. It seemed to just make the clatter louder. The diode did not burn out, but it didn't help the clatter any, so I removed it. After I took it out, the relay stopped chattering and seemed to work ok. The first relay is still buzzing, but it's a very low buzz. If I smack the enclosure it's mounted in with my hand, it will change pitch, sometimes for the better. It's not any louder than the inverter humm. I purchased new relays to replace them, but for now, I'm going to leave the old ones in place since it's going to be a pain in the rear to get them out (operator installation error) and I'm kind of pressed for time right now.

I got most of my electrical back in place. Still have to hook up the A/C and Aquahot lines. Now I can start on getting the generator installed (which is what prompted this whole mess). I'll have to redo a few things after the summer trip, as I'm just trying to get it functional now, and it's not necessarily pretty.

craig

boogiethecat · July 23, 2008, 09:02:26 AM

use four 1N4007's hooked in a bridge configuration; 1000 volt rated, radio shack fodder, if not there, Digikey...cheap...

gumpy · July 23, 2008, 10:23:28 AM

Ok, so effectively, with this setup, you're just supplying a continuous DC current to the coil? Correct?

zxt · July 23, 2008, 04:21:46 PM

Sometimes these types of relays can get some rust between the pole piece and the armature. A cleaning with a scotch brite pad can clear up the buzzing. It is also possible for the pole piece or armature to get a groove wore into it after it has been energized for extended periods of time. In this case a piece of 220 grit sand paper folded over might get the hump smoothed down, if it is to serious, it has to be replaced.

gumpy · July 23, 2008, 08:27:16 PM

So, tonight I tried the bridge rectifier. I didn't have the 1N4007 diodes, but I had used the 1N4004s the other day and they survived, so I twisted some of them together and attached with alligator (galliator?) clips. The results were very promising. The
second relay was clattering away before I put the bridge on. Afterward, it was silent and completely stable. Very impressive.

Now I need to find the specified diodes, and figure out how to mount them so I can attach them to the relays. I'm thinking I can attach ring terminals to them, and attach them to a piece or plastic board along with the control lines to the relays. I can then mount it on the inside of my transfer switch box.

Since I'm running out of time, I may just mount the 1N4004s for the time being. Looks like I may have to redo some of this work after our vacation this summer, as I'm still not satisfied with the layout and access to the electrical box and transfer switch. The generator is just not playing fair and it's placement is becoming a problem. I may end up cutting one of my underfloor ribs to get it installed. It's blocking access to the exhaust and maintenance door. Not my preference, but it may have to be done.

craig

pvcces · July 23, 2008, 11:42:31 PM

Craig, you might prefer a more sanitary setup than a bunch of diodes on a board. Just use a bridge from Radio Shack. They're small and completely sealed except for the connections!

For what it's worth.

Tom Caffrey

gumpy · July 24, 2008, 04:43:41 AM

Quote from: pvcces on July 23, 2008, 11:42:31 PM
Craig, you might prefer a more sanitary setup than a bunch of diodes on a board. Just use a bridge from Radio Shack. They're small and completely sealed except for the connections!

For what it's worth.

Tom Caffrey

Yeah, I was thinking about that. I saw a photo of one when I was looking up what a bridge diode structure was. If I can find some of the IC units, I can probably just solder my lines to it, and mount it on a board somehow. Will have to see what they look like. I think I have some edge connectrors so I might be able to mount it on a PC board, and attach a few wire connectors to it, and mount it with some standoffs inside the panel box.

I have 4 relays in the box, although only 2 are buzzing currently ( heh heh, currently. Get it? Ok, so it wasn't that good. Still, I got a chuckle out of it. So little things amuse little minds.) I should probably mount 4 bridges in there. I might be able to do it with less, though, since some of my control lines feed multiple relays. Will have to go over my schematic in more detail.

This is great. I'm learning some new stuff here. One more thing to postpone the alzheimer's.

So, here's a question. If these relays have a tendency to degrade and start chattering, and the simple fix is to put a bridge on the control lines, why don't the manufactures simply include the bridge in the original design to begin with rather than the shaded pole configuration? Or, why isn't there a simple bridge component already made that can easily be added to the relay when it starts chattering.

DrivingMissLazy · July 24, 2008, 07:17:13 AM

I believe buzzing relays is something that very seldom happens, and cleaning the rust or dirt off the armature generally solves the problem. Also, the relays are designed to have a certain impedance with 60 hertz applied. By applying DC you very easily may exceed the current rating of the unit causing them to overheat and quickly destroy themselves.

Richard

Sam 4106 · July 24, 2008, 09:04:48 AM

Hi Gumpy,
I can't help wondering why you have four relays in your transfer switch. Is your transfer switch a manufactured one or something you home brewed? Why would there be more than two triple pole relays for a 50 amp, 120/240 volt transfer switch? Are you using it to transfer something other than shore and generator power? What functions you are using your transfer switch for?

Thanks, Sam 4106

"Two are buzzing currently"! Is that "pun in cheek" humor?

gumpy · July 24, 2008, 09:28:23 AM

Quote from: Sam 4106 on July 24, 2008, 09:04:48 AM
Hi Gumpy,
I can't help wondering why you have four relays in your transfer switch. Is your transfer switch a manufactured one or something you home brewed? Why would there be more than two triple pole relays for a 50 amp, 120/240 volt transfer switch? Are you using it to transfer something other than shore and generator power? What functions you are using your transfer switch for?

Hi Sam,

How'd your procedure go the other day? Did you get to see the barn raising?

It's a home brew. It also includes neutral/ground bonding for my electrical system, as well as L1-L2 crossover when not on 240V shore line so both busbars in the distribution panel are powered. This is normally done by the dogbone adapter when plugged in, but my system also crosses L1-L2 when on inverter power. Also, I used DPDT relays, not tripple pole, because that's what I could find and afford at the time.

Quote
"Two are buzzing currently"! Is that "pun in cheek" humor?

Yeah, I got a chuckle out of it after I wrote it. Wasn't sure anyone else would find it funny.

pvcces · July 24, 2008, 10:22:04 PM

Yeah, Craig. I thought it was funny.

I see that I forgot that the bridge might apply too much power to the relay coil because of lack of impedance. If you do use the bridge, it might require some resistance in series with the coil to hold the current to no more than the current when using AC.

I brought it up mainly to reduce the strong vibrations caused by the 60 Hz power. I expect that eddy currents in the armature contribute to the buzzing.

For what it's worth.

Tom Caffrey

gumpy · July 25, 2008, 03:57:36 AM

So, how does one go about figuring out how much and what size resistance to put inline?

I suspect it requires some tools more sophisticated than my $3 harbor freight digital multimeter.

Len Silva · July 25, 2008, 05:44:35 AM

Don't you think it would be far simpler to just replace the relays? Or, replace them with DC coils and use a bridge rectifier for each one.

gumpy · July 25, 2008, 05:48:27 AM

Quote from: Len Silva on July 25, 2008, 05:44:35 AM
Don't you think it would be far simpler to just replace the relays? Or, replace them with DC coils and use a bridge rectifier for each one.

Oh come on. Now you're just trying to be logical! That's not what we do. What fun would that be? What would I learn by just replacing them? I already know how to turn a screwdriver.

This isn't about practicallity. If it were, I probably shouldn't even own a bus