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3 Phase Electrical Formulas

Before starting we should know what a phase mean. Basically it relates to the timing of magnet which passes over the coil at different times. So a 3 – phase – electrical – formula is nothing more than having two extra coils which is slightly out of time with the first coil. In a 3 – phase – electrical we would be having 3 coils for each pair of magnet. In each cycle of power a 3 – phase – electric system have three voltage and current wave which is form are 120 degree offset . By this we mean that every single voltage wave has a phase difference of 120 degree to the other voltage wave form. Each current wave form also ha s a phase difference of 120 degree to the other current wave form. The definition of three phase power states that three individual single phase power is carried out by 3 separate power circuit in an electrical system. An ideal 3 – phase – electrical system implies balanced system. If one of the three phase voltage is not equal to the other than a three phase system is said to be unbalanced. Even the value of phase angle in between the respective phases is not exactly equal to 120 degree.

Generation of three phase power is more economical than generation of single phase power. There are some other advantages of three phase power over single phase power. Like to start a single phase motor we have to apply some auxiliary mean but on other hand three phase motor start itself without providing any external mean. In ratings also three phase machines is 1.5 time good as compare to single phase machine. A three phase power is more preferable for high tension power loads as compare to single phase. Single phase power equation is time dependent function on other hand three phase power equation is time independent constant function.

By this we mean that single phase motor is of pulsating nature which in return produces excessive vibration in large rated motor. Three phase system have good efficiency and also great power factor as compare to single phase system. Other fact about three phase is that most electric power in world is three phase. In a same power range three phases is 150 % more efficient than single phase. In three phase system the power never drop to zero on other hand in single phase power drop to zero three times during the cycle. In three phase system the power which is delivered to the load is same at any instant. It is not in single phase system. 75 % is the size of the conductors is needed in three phase system to have an output of same power which we have from single phase.  By this we can see that three phase power is all the way good for us if we compare to single phase. For our house hold appliance we may need single phase system but as we know that three phase is a lot better from single phase. We have set category of distribution of phase for residential for commercial and for other also.

Question:here in our place we have two types of power voltage supplying our community. one is three phase 220v / 60 hz.the line to ground or neutral voltage is 110v and phase to phase is 220v. the other supply is 3 phase 380v. the voltage from line to neutral is 220v and line to line is 380v. Now according to my electrical instructor that the formula of computing total load in ampere for three phase supply is.. I = total load in watts times power factor divided by square root of 3 times 220V.. question is where did 220v came from.. what about the 3 phase 380v or the 3 phase 220v power supply.. please help me

Answers:For 3-phase calculations: P = sqrt(3) V I pf where P = 3-phase power load, watts V = Line-to-line voltage, volts I = Line current, amperes pf = power factor The 380/220 is indeed a 3-phase system because 380/1.732 = 220 But the 220/110 is not a 3-phase system, 220/1.732 is not equal to 110. The secondary winding (220 volts) of the single-phase distribution transformer is center-tapped to produce 220/110 volts supply.

Question:I know that the voltage from phase to phase is 380V when line power (phase to neutral) is 220V, this means 220*sqrt(3)=380, but how you can prove this formula?

Answers:Prove it graphically. The three phases are 120 electrical degrees apart. Draw a line with a length of 220. Draw another line with a length of 220 so the two make a 120 angle between the two. Measure the length of the third side of the triangle. You'll find that it is 380. If you bisect the 120 angle, you'll have two right triangles with angles of 30, 60, and 90. See the proof in the attached link to derive the 3 factor.

Question:Also, what phase is my 240volt stove and dryer ?

Answers:you are single phase- don't worry about it.(residential) 2 hots 3 phase- commercial and industrial 3 hots 2 phase- heavy industrial(vary rare) 4 hots

Question:Electrical Engineering

Answers:If V is the phase to neutral voltage and I the phase current then, in a balanced system: Power P = 3.V.I.cos where is the power factor angle. Try saying please next time.