Before we discuss about this circuit, the first thing is to discuss about the power system.
Power System
The power system used three phase circuits , this means that the alternating current(AC) have three different phases.(see below)
But why three phases?
There are two reasons for this:
1. Three-phase generators can be driven by constant force or torque.
2. Industrial applications, such as high-power motors, welding equipments, have constant power output if they are three-phase systems
How ac generator work?
If you know about the electromagnetism theory, that there is an electric field present in a wire. This had been proven by the famous scientist Micheal Faraday. That there is a current present in a wire when there is a magnetic force acting on it.
One-phase voltage sources
Three-phase circuits
CONFIGURATION OF THREE PHASE CIRCUIT SYSTEM
Wye (left) and Delta (right) connected voltage sources
Va = Vb = Vc same magnitude but the angle is different by a factor of 120 degree.
The figure below is the circuit for a three phase circuit ( Y-Y)
This is a sample of Y-Y circuit. Load is combination of the load and line impedance ( Zy). And in the end of it is the neutral.
To solve this kind of problem, we should only get one of those three phase circuit because the value used is just equal. To solve for the line current ( that is going to the line impedance) use the ohm’s law I = V/Zy. Used this formula but have different angle.
If Load is Delta, The Zy divide it by 3.
If the Voltage source, Vp/sqr(3) ( θ old – 30)
SEQUENCES
abc (positive) sequence b is lag a by 120 degree.
acb (negative) sequence b is lead a by 120 degree.
FranCircuit 2 