Splitpair Premium Member join:2000-07-29 Cow Towne |
to nelamvr6
Re: AC Wiring causes wierd chirping soundsaid by nelamvr6:Why exactly are these wires moving against each other? Because they are handling rather large loads. The inductive field between the current carrying conductors will cause them to attract or move away from one and another. This movement will make noises. Wayne |
|
|
nelamvr6High-End Headphoniac Premium Member join:2000-11-28 New London, CT |
nelamvr6
Premium Member
2006-Jun-27 8:10 pm
said by Splitpair:said by nelamvr6:Why exactly are these wires moving against each other? Because they are handling rather large loads. The inductive field between the current carrying conductors will cause them to attract or move away from one and another. This movement will make noises. Wayne Uh...no. The wires found in houses are either copper or aluminum, most often copper. The magnetic fields around a conductor are not strong enough to attract either aluminum or copper. Try and see if you can pick up a penny or an aluminum can with a magnet. Even a really strong magnet will not be able to attract copper or aluminum. Not to mention that most houses don't have wires in conduits but instead use romex. |
|
jig join:2001-01-05 Hacienda Heights, CA |
jig
Member
2006-Jun-27 8:46 pm
its not about attracting inert metal, its a metal carrying a current. regardless, i don't see those generating 9600hz |
|
drjim MVM join:2000-06-13 Long Beach, CA |
to nelamvr6
Uh...YES The wires themselves produce the magnetic field, and as long as current is flowing in them, there WILL be a magnetic field surrounding them. You don't normally notice it, because the fields are balanced and in-phase, so there's no magnetic attraction or repulsion. AC induction motors use a rotating magnetic field caused by the current flowing through the stator windings to induce a counter EMF and magnetic field in the rotor, producing the torque that turns the rotor. If you have a large current imbalance in parallel conductors, the field surrounding one wire will be much stronger and possibly out-of-phase, depending on the load, resulting in the conductors moving relative to each other. I've SEEN 0000 conductors carrying AC move around under heavy load when the currents in each phase were highly unbalanced. |
|
nelamvr6High-End Headphoniac Premium Member join:2000-11-28 New London, CT |
nelamvr6
Premium Member
2006-Jun-27 9:18 pm
said by drjim:Uh...YES The wires themselves produce the magnetic field, and as long as current is flowing in them, there WILL be a magnetic field surrounding them. You don't normally notice it, because the fields are balanced and in-phase, so there's no magnetic attraction or repulsion. AC induction motors use a rotating magnetic field caused by the current flowing through the stator windings to induce a counter EMF and magnetic field in the rotor, producing the torque that turns the rotor. If you have a large current imbalance in parallel conductors, the field surrounding one wire will be much stronger and possibly out-of-phase, depending on the load, resulting in the conductors moving relative to each other. I've SEEN 0000 conductors carrying AC move around under heavy load when the currents in each phase were highly unbalanced. No. There is a world of difference between wires formed into a coil and wires lying parallel in a straight line. And we are not talking about 0000 conductors. We are talking about household wiring. There will be no attraction between the two copper wires in a run of romex. Or at least the attraction will be so slight that there will be no movement between the two. |
|
drjim MVM join:2000-06-13 Long Beach, CA |
drjim
MVM
2006-Jun-27 9:39 pm
I'll give you the points for wires in Romex, but you're just flat wrong about about parallel wires in a flat plane. |
|
nelamvr6High-End Headphoniac Premium Member join:2000-11-28 New London, CT |
nelamvr6
Premium Member
2006-Jun-27 10:05 pm
said by drjim:I'll give you the points for wires in Romex, but you're just flat wrong about about parallel wires in a flat plane. No, I respectfully disagree. Copper wires work very well as electro-magnets when formed into coils. But there would have to be a very large current passing through a straight length of copper to produce a magnetic field strong enough to attract another straight piece of copper. Way more current than would be found in a household circuit. |
|
tmaertinCrash Into Me Premium Member join:2002-04-03 North Tonawanda, NY |
to nelamvr6
nelamvr6 - just an FYI - the amount of copper in a penny now is too small to test this. If you have a penny minted pre 1982 this would work. The price of copper increased that year - the US Mint changed the penny to a ratio of 97.5% zinc and 2.5% copper. as far as the issue at hand, if you find the product on the web link below around the house - someone is messing with you. I cant believe they actually make this: » www.shomer-tec.com/site/ ··· C99BE7CC |
|
nelamvr6High-End Headphoniac Premium Member join:2000-11-28 New London, CT 1 edit |
nelamvr6
Premium Member
2006-Jun-27 10:46 pm
said by tmaertin:nelamvr6 - just an FYI - the amount of copper in a penny now is too small to test this. If you have a penny minted pre 1982 this would work. The price of copper increased that year - the US Mint changed the penny to a ratio of 97.5% zinc and 2.5% copper. as far as the issue at hand, if you find the product on the web link below around the house - someone is messing with you. I cant believe they actually make this: » www.shomer-tec.com/site/ ··· C99BE7CC You know I was already aware of this, I was wondering if anyone would point this out! (The penny's copper content that is, not the device in your link.) But my point was that copper is extremely difficult to magnetize. |
|
tmaertinCrash Into Me Premium Member join:2002-04-03 North Tonawanda, NY |
tmaertin
Premium Member
2006-Jun-27 10:52 pm
cmon now...tell the truth...you own the Mind Molester lol! |
|
chuckkk join:2001-11-10 Warner Robins, GA |
to nelamvr6
Actually, copper wire can move due to heating or repulsion. 30 years ago, I worked in a GE test lab. We had a "High Current" test facility that was able to dump 1000 amps at 1000 volts (3 phase) into a dead short. When testing at high current, parallel copper wires connected to the same phase were repelled with enough force to brake fiberglass tape used to help route the wiring to the device under test. The control room had a large armor glass window on the wall of the test chamber. We had molten copper from the device under test sprayed on the armor glass on more than one occasion. It was found necessary to put a piece of plexiglass in front of the armor glass to protect the glass from pitting. Naturally, the plexiglass sheet would be very much the worse for wear after one test shot. The test generator had a 25 ton spinning assembly, and was powered with a several thousand horsepower motor. The motor was powered directly with the high line voltage feeding the whole city. There was a solid state controller that controlled the motor spinup to prevent the rotor starting currents from being excessive. Oil pressure on the bearings was about 5000 PSI.
Some possible electrical sources of chirps in a home: Fire Alarm or Burgler Alarm Oven or the Fridge Electromic Thermostat Answering Machine Clock Radio Fan in air handler, outside A/C unit, or furnace during starting Ceiling Fan Land line electronic phone when the line is checked Electronic ballast Lawn sprinkler system timers Water softener (To name a few)
|
|
|
nelamvr6High-End Headphoniac Premium Member join:2000-11-28 New London, CT |
nelamvr6
Premium Member
2006-Jun-28 1:01 am
said by chuckkk:Actually, copper wire can move due to heating or repulsion. 30 years ago, I worked in a GE test lab. We had a "High Current" test facility that was able to dump 1000 amps at 1000 volts (3 phase) into a dead short. When testing at high current, parallel copper wires connected to the same phase were repelled with enough force to brake fiberglass tape used to help route the wiring to the device under test. The control room had a large armor glass window on the wall of the test chamber. We had molten copper from the device under test sprayed on the armor glass on more than one occasion. It was found necessary to put a piece of plexiglass in front of the armor glass to protect the glass from pitting. Naturally, the plexiglass sheet would be very much the worse for wear after one test shot. The test generator had a 25 ton spinning assembly, and was powered with a several thousand horsepower motor. The motor was powered directly with the high line voltage feeding the whole city. There was a solid state controller that controlled the motor spinup to prevent the rotor starting currents from being excessive. Oil pressure on the bearings was about 5000 PSI. Surely you're not suggesting that this is similar to the usage of romex in a household circuit? 1000 amps is a lot of juice. Do you feel that there will be movement in the conductors of a romex run in ordinary household wiring? |
|
Splitpair Premium Member join:2000-07-29 Cow Towne |
to nelamvr6
said by nelamvr6:The wires found in houses are either copper or aluminum, most often copper. The magnetic fields around a conductor are not strong enough to attract either aluminum or copper. Incorrect, totally incorrect. They type of conductor is irrelevant it is the current flowing thru the conductor that is relevant. Not to mention that most houses don't have wires in conduits but instead use romex. No so my home is an older structure and its wiring is in emt. Wayne |
|
fireflierCoffee. . .Need Coffee Premium Member join:2001-05-25 Limbo 1 edit |
to nelamvr6
Guess I'll have to respsectfully disagree with you. While I don't believe the sound is caused by the specific wiring issue cited (because it's happened in how many different houses?), parallel copper (or aluminum or steel or silver) wires each carrying current do exhibit an attraction or repulsion whose strength is based on:
Their distance The current in each conductor The permeability constant of the medium between them.
You can determine the magnetic force between the conductors with the equation:
F/l=mu0*I1*I2/2pi*D
where mu0 = Pi*4E-7 (for air), I1 is the current in one conductor, I2 is the current in the second conductor, and D is the distance between the two. This equation can be found in virtually any college physics book and demonstrates that magnetic attraction between conductors (both carrying current) in this arrangement has nothing to do with the interaction of a magnetic field to a metal but a magnetic field to another magnetic field as both conductors have their own magnetic field.
If you run the math on two conductors with 10A spaced 1E-3 M (1 millimeter) apart, you will get a field strength of roughly 2E-2 Tesla which is considerably stronger than the Earth's magnetic field strength of 60E-6 T at roughly the strongest point. Given that 12AWG house wiring can accommodate up to 20A, the field strength between the conductors could be higher.
One point that should be noted however: The "hot" and "neutral" conductors in "romex" are carrying currents in opposite directions to one another (yes I realize AC changes direction but the current in the hot and neutral remain opposite) and by the right hand rule, conductors carrying opposing currents cause conductors to repel each other, not attract though it could still impart mechanical stresses on the conductors which *might* make them vibrate under special conditions.
Having said that, if the OP has determined that the frequency of the sound is 9600 Hz, then magnetic coupling is not the issue as it would (if it made any noise at all) be a 60 Hz-sounding hum. The cardboard material separating the insulated conductors in romex would probably also serve to dampen any noises they might make resulting from mechanical vibration. |
|
fireflier |
to Splitpair
Mostly correct--it is the current flowing through TWO interacting conductors that is relevant. And yes you are correct, the conductor material (assuming it can conduct) is irrelevant for a situation in which two current carrying conductors interact with one another. |
|