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Old 12-18-2008, 12:07 PM   #1
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3 phase power phase question


I am installing a camera system that uses the wiring as the cable to transmit on. In a business setting it will only work on 1 of the 3 phases. Inother words it will NOT work across phases. My question is, without trial and error, connecting and trying each camera. IS there a device and I can plug in each recept to see if it's on the same phase as the other reecpticle ?
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Old 12-18-2008, 03:28 PM   #2
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3 phase power phase question


Try re-posting in the Electrical forum.

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Old 12-18-2008, 04:09 PM   #3
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3 phase power phase question


Measuring from the hot terminal of one receptacle to the hot terminal of another with a DVM, you will read less than ~3 vac if they are on the same Φ.

Last edited by Yoyizit; 12-18-2008 at 07:35 PM.
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Old 12-18-2008, 04:20 PM   #4
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3 phase power phase question


That would be alot cheaper than a circuit tracer.
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Old 12-18-2008, 07:56 PM   #5
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3 phase power phase question


I would imagine your talking about 208Y120 3 phase. Phase to phase is 208 volts. Any of the 3 phases to neutral is 120 volts. It won't matter what receptacle you plug into as they are all phase to neutral if you are talking about 120 volt wall receptacles like you have in your home.
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Old 12-18-2008, 08:34 PM   #6
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3 phase power phase question


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Originally Posted by jelliott View Post
I am installing a camera system that uses the wiring as the cable to transmit on. In a business setting it will only work on 1 of the 3 phases. Inother words it will NOT work across phases. My question is, without trial and error, connecting and trying each camera. IS there a device and I can plug in each recept to see if it's on the same phase as the other reecpticle ?
Thanks
You could also just turn the breakers off to see what recept is on which phase. Every 3 breakers vertically will repeat phases. So, if the first breaker is A, the second B and the 3rd C, then the 4th will be A. It goes ABCABCABC etc.
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Old 12-18-2008, 08:42 PM   #7
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3 phase power phase question


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I would imagine your talking about 208Y120 3 phase. Phase to phase is 208 volts. Any of the 3 phases to neutral is 120 volts. It won't matter what receptacle you plug into as they are all phase to neutral if you are talking about 120 volt wall receptacles like you have in your home.
His problem is that the video signal will not travel through the transformer secondary windings.
For this reason, only receptacles wired to the same phase can be used.
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Old 12-18-2008, 08:52 PM   #8
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3 phase power phase question


Yes of course I see what your saying...thanks.... I thought he was saying he couldn't connect across phases. He needs to be on the same phase conductor ...gotcha.
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Old 12-18-2008, 09:01 PM   #9
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3 phase power phase question


A very long (say 50 foot) single conductor with a regular power plug at the end, the wire is connected to the smaller prong (not the neutral). A short (say 2 foot) conductor connected to a regular power plug, smaller prong. A small board with two ordinary (porcelain?) lamp sockets connected to each other with one jumper wire, each with the same kind of small incandescent lamp. Connect the single conductors to the free terminals of the lamp sockets.

You now have a test instrument for what you want to do. If the lamps come on when the ends are plugged into different receptacles then the receptacles are on different phases. You needed two lamps (in series) to handle the 208 or 240* volts phase to phase.

* The same dilemma exists with single phase 120/240 volt systems; the video or radio frequency equipment all has to be plugged into the same "side of the line".

Last edited by AllanJ; 12-18-2008 at 09:05 PM.
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Old 12-19-2008, 09:29 AM   #10
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3 phase power phase question


You should also be able to purchase a "bridge" which would allow the carrier signal from the camera to travel across phases.
These devices are installed in the service panel, using 15A breakers.
You would need one specifically designed for a 3-phase system to allow the signal to travel across all phases.
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Old 12-19-2008, 09:56 AM   #11
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You should also be able to purchase a "bridge" which would allow the carrier signal from the camera to travel across phases.
These devices are installed in the service panel, using 15A breakers.
You would need one specifically designed for a 3-phase system to allow the signal to travel across all phases.
Which is probably a high pass filter.
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Old 12-19-2008, 10:02 AM   #12
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3 phase power phase question


I wonder, just as a theoretical question, if placing three equally sized lamps on all the phases with a wye connected floating neutral would pass the signal? In other words, if you had three lamps sockets, and wired all three silver terminals together, but not to a neutral from the panel, and wired the three brass terminals to each phase, the lamps would burn with equal brightness. Would the signal cross these loads?
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Old 12-19-2008, 10:32 AM   #13
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I wonder, just as a theoretical question, if placing three equally sized lamps on all the phases with a wye connected floating neutral would pass the signal? In other words, if you had three lamps sockets, and wired all three silver terminals together, but not to a neutral from the panel, and wired the three brass terminals to each phase, the lamps would burn with equal brightness. Would the signal cross these loads?
The hot resistance of a 120v, 100w bulb is about 140Ω. If the signal source impedance is 75Ω, your destination signal would be reduced to ~ half the normal voltage and ~1/4th the normal power. There'd also be reflections because the Characteristic Impedance of the circuit (75Ω) is not maintained.
It might work, anyway.
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Old 12-19-2008, 12:45 PM   #14
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3 phase power phase question


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Originally Posted by Yoyizit View Post
The hot resistance of a 120v, 100w bulb is about 140Ω. If the signal source impedance is 75Ω, your destination signal would be reduced to ~ half the normal voltage and ~1/4th the normal power. There'd also be reflections because the Characteristic Impedance of the circuit (75Ω) is not maintained.
It might work, anyway.
A LC filter would be simpler! Just a coil and capacitor in series. Perhaps 3 filters, phase to phase would do!
Thirty years ago, I used to play with this sort of thing. But, now i've forgotten.There are formula's to apply, and I would think that any electrical tech. worth his salt would come up with the answer in a minute!
See this site http://en.wikipedia.org/wiki/LC_circuit

Last edited by Wildie; 12-19-2008 at 01:02 PM.
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Old 12-20-2008, 12:49 PM   #15
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3 phase power phase question


Search for "Phase Coupling", its done a lot with X10 systems in houses where there are multiple interfaces through out a house.

http://kbase.x10.com/wiki/Phase_Coupling

If you have an electric dryer outlet, this would be an easy install (also available in the 4pin variety as well)
http://www.smarthome.com/4826B/Signa...epeater/p.aspx

Though you would probably need two to couple between all three phases.

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