2007-02-26 13:36:15 · 4 answers · asked by shaker 1 in Science & Mathematics ➔ Engineering
In a 3 phase system where the phase to phase voltage is 208V, the phase to neutral voltage will be 120V. This is north american residential distribution.
In industrial installations, other voltages are commonly used for 3-phase distribution: Canada 575V, USA 480V, Europe 380V, etc.
2007-02-26 14:51:36 · answer #1 · answered by Eng_helper 2 · 0⤊ 0⤋
the output of this transformer is usually star connected with the standard mains voltage (120 V in North America and 230 V in Europe) being the phase-neutral voltage. Another system commonly seen in North America is to have a delta connected secondary with a centre tap on one of the windings supplying the ground and neutral. This allows for 240 V three phase as well as three different single phase voltages (120 V between two of the phases and the neutral, 208 V between the third phase (known as a wild leg) and neutral and 240 V between any two phases) to be made available from the same supply.
While most three-phase motors are very big (>750w), there are small (<50w) three-phase motors. The most common example is a computer fan. An inverter circuit inside the fan converts DC to three-phase AC. This is done to decrease noise (as the torque from a three-phase motor is very smooth compared to that from a single phase motor or a brushed DC motor) and increase reliability (as there are no brushes to wear out, unlike a brushed DC motor).
2007-02-26 21:57:51 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Good question.
You may go back to the fundamental of electrical system.
Draw a STAR Circuit, and from the center of the star is your Neutral & earth. Disregard the Earth for the time being, and each wing is consider 1 phase. So.. you have 3 wings, and that is why you have 3 Phase.
If you use a voltmeter to measure From Phase to Neutral, you will get ~240V +-10% or 127 +- 10% depending on which country.
If you meausre phase to phase, you will get ~415V +- 10% or 220 +- 10% depending on which country.
Provided if my memory doesn't fails me, i will guess the figure is correct.
So, your answer is depending on how you measure the voltage.
2007-02-26 23:20:29 · answer #3 · answered by Mr. Logic 3 · 0⤊ 0⤋
Typically, 3 phase is used at 208V.
Through the transmission system the votlage goes up and down. But when it comes time to run motors etc 3 phase is usually 208VAC.
2007-02-26 21:54:03 · answer #4 · answered by Lost in PA 2 · 0⤊ 0⤋