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Lord Garth
Guest
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 Posted:
Sun Apr 10, 2005 6:10 am Post subject:
Re: About 3-phase AC |
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| Quote: | Bob Eldred wrote:
snip
It's still common in the US where houses are mixed with small motor
installations. That unexpected 208-to-neutral is(was) a problem on
water-well controls when you needed 120v for the control-circuit.
WAde H
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Around here, all delta circuits are being replaced with a wye configuration.
The utility has standardized on this...then all the other power utilities
came
on the scene so who knows !
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Bob Eldred
Guest
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| Posted:
Sun Apr 10, 2005 9:10 pm Post subject:
Re: About 3-phase AC |
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Well, that certainly makes more sense than some sort of a nutty asymetrical
grounding scheme. Oh well, based on the above comments, I guess anything is
possible. What does the NEC have to say about it?
Bob |
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Don Kelly
Guest
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| Posted:
Tue Apr 12, 2005 6:10 am Post subject:
Re: About 3-phase AC |
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| Quote: | I think you got something wrong, or I didn't expressed it correclty!
Say you have two AC sources of 110V, now if I put them in series they
should add up to give 220V if their instantaneous phases are same(0 or
360) or if they are 180 phase out they should sum up to zero. I think
these two AC sources are just like two phases of 3-phase AC supply
which are 120degree phase apart. And they should give a voltage less
than 220V when summed up.
Any Help...Thanks
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Your two single phase 110 sources in series will give 220V or 0 depending on
connection. This is the Edison or 3 wire single phase system in the 220V
case (and something useless in the other case) which is a common North
American configuration. In Europe, where it is not used, it is called a 2
phase system and if one defines an phase system as having n voltages to
neutralThere are two basic forms of a 3 phase connection -star in which
there is a common neutral or delta where there is no neutral. .You mention a
voltage of 110V to neutral so the corresponding voltage between lines is
110*root(3)=190V.
In a star connected 3 phase system the phase and line currents are the same
but line to line voltages are greater than phase to neutral voltages by the
factor of root(3). In a delta the phase and line to line voltages are the
same but the line (external) currents are root(3) times the phase (internal)
currents.
There are advantages and disadvantages to both and advantages for 3 phase
over single phase (2 or 3 wire), particularly in rotating machines and
transformers.
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer
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gonzo223
Joined: 24 Aug 2006
Posts: 1
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Thu Aug 24, 2006 3:25 am Post subject:
Need some related advice |
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Wow, I hope some of you from this forum would be as confused about my job or some of my interests as I am about what I've read so far in this forum...
I just need to know what's required to hook up a 220v 3 phase motor in my residential home.
I hooked it up to my standard 220v connection and it worked fine for a while. Here's where it gets hairy...
The motor would twitch, but when I have it a spin befor putting power to it, it would run fine and at full speed.
The next time I tried to get her going, it just twitched a little bit and blew a fuse.
I finally started researching and found that switching 2 wires would determine what direction the motor spun. I changed wires around a few times and blew fuse after fuse.
I did a little more web crawling looking for any help and that brought me here.
This is probably pretty obvious to anyone here, but what exactally do I need to get my 3 phase motor running on whatever 220v power it is that runs my dryer.
Thanks for putting up with my question... |
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neon
Joined: 25 Feb 2006
Posts: 570
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Sun Oct 29, 2006 11:26 am Post subject:
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| What delta and Y transformer has to do with phase i don't know. they both recieve the same input on a delta the output will be one half of the voltage of a Y TRANSFORMER. 3 phase means 360 degrees devided by 3 or 120 degrees apart therefore any one time the voltage will be that 120 degrees differential no matter what voltage there is. |
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neon
Joined: 25 Feb 2006
Posts: 570
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Sun Oct 29, 2006 11:42 am Post subject:
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| at the generating stationthe power is sent to hi power transmission line in the form of 375kv which goes into a substation which in turn transforms it down to about 16kv for local distribution when it gets to the pole it is transform down to to 120v from a Y TRANSFORMER 3 PHASES that what you get one phase neds more then use another tap for more power and so on. all of you must understand Y transformers to get the concept read about it. |
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