what is the difference between single phase and three phase current?

Answer 1

Imagine a wheel rolling down the road. If you marked one point on the wheel it would be a single phase of sign wave rising and falling relative to the road. If you marked 3 points on equal thirds of the wheel you would have 3 phases of sign wave relative to the road.

3 phase power is very efficient for electrical motors as the motor can be built to have three poles giving a constant torque with a constant rotating magnetic vector.

Single phase (including 220v) is typically used for everything else. 220 is often incorrectly called 2 phase because the two legs are 180 degrees out of phase with each other and both vary relative to common or ground, but since the ground is never used, it is still considered single phase.

Answer 2

Have you ever done any singing in rounds? ''Row, row, row your boat, merrily, merrily....'' When the first group reaches merrily, the second starts ''Row''. Eventually you have 3 different groups singing the same thing at different times. So 3 phase. In addition to the familiar sine wave of single phase, 3 phase has a second phase starting 120 degrees after the first, and a third phase at 240 degrees. The big advantage to 3 phase is that motors can be smaller for the same horse power. Just as a single phase AC motor is smaller than a similar DC motor, so a 3 phase motor is smaller than a single phase. Airplanes use electric motors with even more phases where weight is even more important then size. In factories, it is common to have many high loads, and most of them use 3 phase motors and 240 or 480 volts. I once managed a small factory where almost everything was 480 3 phase or pneumatic. We had 3 phase motors ranging from 1/4 horse to 600 horsepower. I wouldn't even want to think about a 120 volt single phase 600 horse motor, or the conductors it would take to supply it. Most of the lighting was 277 volts pulling power from one phase of the 3 phase. The phases were 480 apart, but only 277 above ground. It is also easy to reverse a 3 phase motor, just switch any 2 leads. I even selected a vacuum cleaner that ran on compressed air because we weren't wired up to supply enough single phase 120 volts to run a large shop vac. Perhaps the biggest advantage to single phase is that it is the way it has always been done. It works well with incandescent lights and other resistive loads too. It certainly is easy to understand why we stick to 120 volts in our houses. Enough people kill themselves with it, let alone 480.

Answer 3

Actually, the phase difference is 120 degrees (3 x 120 = 360). Draw a Y - label the center N, label the ends A, B and C.
These are transformer windings of the load side (where the power is used) of the transformer that used to hang on the poll outside every home - one transformer fed 10 homes or so. In new construction these are nearly always underground.

The tap labelled N is the neutral. Each winding offers 110 volts (or so). Attach your dryer to A and B, 220 volts. Same for A and C or C and B.

Now, imagine a motor with three windings that produce a magnetic field. The windings are attached to A and B, B and C, and A and C in succession. Because the current is in three phases, 120 degrees apart, the magnet inside (attached to the rotor) will be forced to "chase" the magnetic field.

Voila - conversion of electrical energy into mechanical energy.

Answer 4

First-You cannot run single phase devices on three phase power or three phase devices on single phase power.

Single phase is one input line carrying one sinusoidally varying input power. there is a single power line, a ground and a neutral line. Single phase is typically used residential electric power.

In three phase there are three power lines that supply sinusoidially varing power. Each phase is called a "leg". If the power in tehse lines was "in phase" then they would all have their peaks, valleys, and other points at the same time. If they do not then they are said to be "out of phase". The phase difference or the difference between, say, the peaks of two phases is called the phase difference; and is usually expressed in degrees. Three phase can be split off onto three single phase lines. Power companies do this on residential power lines. Three phase power is typically used in large electric machinery such as very large electric motors, or steel mills.

Answer 5

Assume, a 50 amphere 3 phase supply source is available.
Ina single phase utility, you can draw a 50 amps current in each phase with neutral terminal.(ie) 3x50=150 amps of single phase current can be used.
But in three phase utility, you can draw 50 amps current only.

Answer 6

Hard to explain clearly without a diagram.
Try ; http://en.wikipedia.org/wiki/Three-phase
Do be aware that single phase power can be
one of four variations of two legs of a three
phase system, the fourth being with one "line"
being a center-tapped ground.
Also wiki 'Three phase four wire`

Answer 7

u can use a single phase supplt to power a 3 phase motot but u will need an inverter to do this

Answer 8

Single and three phase. Single is DC (direct current) and three phase is AC(alternating current).

DC is easy think of one wire and it has 5 volts on it, AC think of three wires they all have a voltage on them but they are 120 degrees apart from each other.

DC is is normally always converted from AC, think of a phone charger.

Answer 9

http://en.wikipedia.org/wiki/Single-phase_electric_power
http://en.wikipedia.org/wiki/Three-phase_electric_power