Discussion in 'General Electronics Discussion' started by Joel1, Sep 30, 2018.

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1. ### Joel1

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Sep 30, 2018
I am new to dealing with A/C electricity. I know that when one is using D/C you just need 2 wires. However, with A/C I see that three wires are being used...why?

Also how does one split the electrical output of an A/C generator?

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,178
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Jan 21, 2010
Both AC and DC can be carried on 2 conductors.

Your 3 wire motor uses a pattern of three AC waveforms with a phase relationship to each other to make it work (I'm assuming here, because you don't give any information). When you soon it, you get a combination of three AC waveforms, one on each pair of wires.

What do you mean by "split the electrical output?"

3. ### Cannonball

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May 6, 2017
AC can be transmitted on two wires. The third wire is for safety. AC coming out of the main breaker box and has a white wire, a black wire and a green wire. All of the white
wires are connected together and are called the neutral wire.
The third wire is green and it connects to the metal part of switches and receptacles and goes back to the metal part of the breaker box.

If you exchange the white wire with the black any where in the circuit you will have short in the circuit which will trip the breaker in the main breaker to prevent anyone from being shocked.

4. ### Audioguru

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Sep 24, 2016
The motors shown in the photos look like small brushless hobby motors that have 3 wires, one wire for each phase of the AC. It looks like the motor in the second photo is a generator driving an LED and looks the same as motor talked about and driven as a windmill generator on another website.

5. ### hevans1944Hop - AC8NS

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Jun 21, 2012
Three wires are used in two instances. One instance is ordinary house wiring, where one wire (white) is the "neutral" or AC return wire; a second wire (black or red) is the "hot" or AC supply wire; and a third wire (green) is the "safety" ground wire.

Each "hot" or AC supply wire is supplied current from a circuit breaker or a GFCI-equipped circuit breaker. Each "neutral" or AC return wire is connected to a "neutral" bar in the distribution cabinet, along with all the other "neutral" wires from other AC circuits powered from other circuit breakers in the distribution cabinet. The neutral bar is connected, in the distribution cabinet, to a purpose-driven earth ground located near the service entrance panel. Each "safety" ground wire is connected to a separate ground distribution bar that is electrically bonded to a purpose-driven earth ground.

Power tools and motors that are "double insulated" need not use the green safety ground, which is normally electrically bonded to the conductive exterior of the tool or motor case to provide a short-circuit path back to the neutral if the tool or motor should develop an internal conductive path from the "hot" AC line to the exterior case of the tool or motor. In such a circumstance, either the circuit breaker in series with the "hot" AC line will trip, or a ground-fault circuit interrupter (GFCI) will trip to remove voltage to the "hot" AC line. In either instance, AC power is prevented from being applied to the exterior conductive parts of the tool or motor.

I don't know what you mean by this question. Split the electrical output of an A/C generator in what manner?

AC is generated by the utility service for long distance transmission as three-phase alternating current. Each phase is 120 degrees apart from adjacent phases. It can be shown that this arrangement will create a spatially rotating, constant amplitude, magnetic field when the three phases are used to excite the poles of an AC induction motor. Depending on design, the three phases (A, B, and C) may connect to loads in a delta arrangement without a common "neutral" or in a star or "Y" arrangement with a common neutral.

The AC is generated at a moderately high voltage by alternators at the utility service, than it is transformed to really high voltages (with transformers of course) for transmission to distribution sites where transformers are again used to reduce the voltage to more practical usable levels for distribution to neighborhood homes and businesses. All this is done as three-phase transmission, generally requiring three transformers (one for each phase) as the voltage is successively reduced. Most homes are served by only one of the three phases, applied to a single transformer with a center-tapped secondary. This transformer often serves several homes simultaneously.

When mounted on a pole (instead of underground or in a transformer vault) this transformer is called a "pole pig." The center tapped secondary, which is connected to the "neutral" of the house distribution panel, provides 120 VAC between each of the two end terminals of the secondary winding and the center tap of the secondary winding. These two 120 VAC distributions are 180 degrees out of phase with each other, but it is still considered to be single phase distribution. Connections between the end terminals provide 240 VAC for heavier loads, things like whole-house HVAC systems, cooking ranges, and water heaters.

It is also possible to create spatially rotating, non-constant, magnetic fields using just two phases, separated by 90 degrees. Some early power generation and distribution systems toyed with this idea until Nikola Tesla and George Westinghouse demonstrated the superiority of the three-phase AC system, initially installed at Niagara Falls on the Canadian and US border.

Many stepper motors used today operate from two-phase AC square waves that are separated in phase by 90 degrees, but three or more phases are also used. You should read about power engineering to get a better handle on AC.

6. ### Joel1

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Sep 30, 2018
ALL - Thank you for your responses, I appreciate them!

To clarify, all of you have talked about green, white, red, or black wires, however the colors of the wires here are blue and yellow. What's the difference?

Also - when I say split the electrical output I mean using the generator to light 2 light bulbs instead of just 1.

lastly, what are the two metal rods sticking out of the light bulb?

Thanks!

7. ### Minder

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Apr 24, 2015
That is one of those cheap 3ph AC generators off ebay, if feeding single phase loads, LED's etc, you can place the LED's across each phase, IOW with 3 LED's, one would connect across PHA & PHB, two across PHB & PHC. three across PHA & PHC.
Although it is AC the LED's will 'self rectify' IOW no need to convert to DC.
m.

8. ### Tha fios agaibh

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Aug 11, 2014
Wire colors depends on electrical codes. This varies by country and application.
I see your from here in the States. In building wiring, the only mandatory colors are green, white (or grey) orange and light blue. Otherwise, they can be any color you want.
If the wires are in a different application such as an appliance or machinery the rules for color are different.

Edit to say, I'd forget about color at this point because its essentially up to the device manufacture to decide what colors they decide to use.

Last edited: Oct 2, 2018
9. ### Minder

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Apr 24, 2015
Those simple ebay (141763227567) 3 ph Alternators are basically for wind vane generators etc, which is what I used one for using a 3 banks of LED's per phase pairs.
They use two yellows and a blue for some reason?
M.

10. ### Minder

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Apr 24, 2015
I have purchased more than one of these units and have never seen any 'Rods' sticking out of the terminals, their presence doesn't make much sense?
They do not appear in your lower Pic?
M.

11. ### Bluejets

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Oct 5, 2014
Op might be referring to the mounting pins on a bc lamp.

Who knows what they're looking at......

12. ### Minder

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Apr 24, 2015
I realize what the OP is referring to now, the shipper includes one LED connected across two phases.
This is the two wires poking out of two of the connections.
M.

13. ### Minder

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Apr 24, 2015
I don't think there is much danger in this case, 5v - 6v 3ph AC!
M.

Last edited by a moderator: Apr 28, 2019
14. ### Minder

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Apr 24, 2015
The OP was concerning an ebay simple 3phase low volt generator, typically used for wind vane LED's
M.

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15. ### davennModerator

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Sep 5, 2009
this is a very old thread
deleted a lot of mis-information and responses

will now close