Describe the Fundamentals of Electrical and Electronic Engineering.
The objective of this experiment is to study and get acquainted with/to a balanced threephase Yto Y connected system. In this experiment, a 3phase Y connected voltage source will be connected to a 3phase Yconnected load with various measurements taken to validate the relationship between line and phase voltages. Students will so be expected to determine the load impedance from the measurements taken during the experiment. The entire experiment will be conducted at 50 Hz. All of the currents and voltages in this experiment are RMS quantities.
The power is generated, transmitted, and distributed in 3phase (3Φ) form. The 3Phase AC supply system has the following advantages:


 It is themost economical wayof generating, transmitting, and distributing electrical energy
 It can supplyawide variety of loads, those that require a threephase supply such as an induction motor, as well as others requiring only a single phase supply
 A balanced threephasesystem ensures asmooth flow of energy from source to load since singlephase power produces a pulsating flow of energy

2.1 Balanced ThreePhase System
Figure 1 shows the circuit diagram of the threephase circuit that will be connected up for this experiment. A threephase Yconnected RLC load bank is to be connected to a Yconnected three phase voltage source.
Figure 2 shows the perphase circuit (phase U) of the load bank. It is possible to alter the phase impedances (ZU, ZV, and ZW) of the load bank individually by adjusting the reactances XU, XV, and XW as well as the resistances RU, RV, and RW in each phase. The reactances and resistances can be adjusted by using the three knobs available on the RLC load bank. In this experiment, a balanced threephase load is required. Therefore, XU = XV = XW and RU = RV = RW. The settings for the reactance and resistances will be provided to you by your lab supervisors during the experiment.
It is also possible to set the load as an inductive or capacitive load by using the 3way switch available on the RLC load bank. If XL is chosen, the power factor will be a positive value and a negative value if XC is chosen.
Please refer to your lecture and tutorial notes for more information in relation to 3Phase systems. Each student is expected to answer the following prelab questions in the space provided by applying the theory gained in lectures and tutorials. The prelab exercises must be completed before the start of the experiment. Students will not be given time before the start of the experiment to do the preliminary work. Students who fail to do their preliminary will not be allowed to carry out the experiment. Completion of the preliminary is important, as this will help students to perform an analysis of the experiment to bring them up to date with the theoretical background.
PreLab Question1: Draw the circuit diagram of a 3phase Yconnected voltage source clearly labelling all phase and line voltages. Also, write down the mathematical formulas that express the relationship between phase voltages, and phase and line voltages. Are the line voltages greater in magnitude or phase voltages?
Line voltage: is the voltage measured between the any twoline segments, line voltage are voltage between two live conductors.
Phase voltage: voltage measured between live and the neutral link of the threephase supply system.
For star connected circuit and for the relation between line and phase current given as
During laboratory experiment we have recorded
Table 1 Observation line and phase voltage
Van 
243 Volts 
Vbn 
242Volts 
Vcn 
239Volts 
Vab 
419Volts 
And from mathematical relationship line voltage is 1.73 times the phase voltage so line voltage is more than the phase voltage
PreLab Question2: Write down the relationship between the peak and RMS values of a voltage. What are the peak and RMS values of the mains voltage in the Australia?
Solution:
The relationship between the peak and RMS values of a voltage is
The main voltage in Australia is 230 V at 50 Hz frequency therefore the RMS value of mains voltage in Australia is 230 V
Preliminary
Thus, the peak value of mains voltage in Australia is
PreLab Question 3: For the following Δ (delta) connected load, if the phase impedance is 18 + 21j ?/Φ, what
PreLab Question 4: What is the neutral current in a 3phase 4 Wire Balanced System? And why?
Solution:
The neutral current is zero in three phase Star configuration in balanced load while it gives some value of current in unbalanced load. In a Star 4 wire system the neutral, in theory, carries only the difference of current flow between the 3 phase conductors. So, when the current in phase A, B and C are equal, then there is no current flow in the neutral. When current flow in phase A only increases, then the neutral current will equal that increase. However, this is true only for purely resistive (linear) loads. Nonlinear loads cause harmonics, some of which will add up on the neutral. Because when you add all the currents together at the neutral they add up to 0 if they are balanced. If balanced current was 10A/ phase then add 10cos(0) + 10cos(120)+10cos(120) = 0 for a 3 phase system. If it's not balanced then add them all together and there will be some current at some angle left over
PreLab Question 5: What is the perunit system? How are the actual circuit quantities (voltages, currents, impedances, etc) converted to their perunit values? If the 3? apparent power (S) rating of a 3phase YtoY connected load is 5 kVA and line voltage is 415 Volts, what would be the base impedance?
Solution:
The per unit system simplifies the analysis of complex power system by choosing a common set of base parameters in terms of which all system quantities are defined
The definition of any quantity (voltage, current, impedance) in per unit system is given as
The
Voltage: the ratio of actual voltage to the base voltage is called the per unit voltage
Vbase base voltage or rated voltage
Current: the ratio of actual current to base current is called p.u. current
Similarly ration of actual impedance to the base impedance is called per unit impedance
Here for given problem
For the singlephase system
And for three phase system
And for current
Base impedance
Measurement Results When X = XL (Inductive Load) 

Quantity 
Value 
XU = XV = XW 
0.5pu=0.5pu=0.5pu 
RU = RV = RW 
0.5pu=0.5pu=0.5pu 
Van 
243 Volts 
Vbn 
242Volts 
Vcn 
239Volts 
Vab 
419Volts 
ILinea 
6.7Amps 
Ineutral 
339Amps 
P? 
780Watts 
Cos θ 
0.48 


 Switchthe load bank off by using onoff switch on the load bank.
 Changethe position of the 3way switch to point to the XC setting
 Reenergiesthe RLC load bank by turning on the onoff switch
 Redothemeasurements and record the values of the circuit quantities in the table provided below

Measurement Results When X = XC (Capacitive Load) 

Quantity 
Value 
XU = XV = XW 
0.5pu=0.5pu=0.5pu 
RU = RV = RW 
0.5pu=0.5pu=0.5pu 
Van 
243 Volts 
Vbn 
242 Volts 
Vcn 
240 Volts 
Vab 
419 Volts 
ILinea 
6Amps 
Ineutral 
1.9 Amps 
P? 
775 Watts 
Cos θ 
0.5 
1) The Preliminary Work
2) Measurements recorded during the experiment including the nameplate information in tabulated form
Nameplate Information of the RLC Load Bank 
Model 
Apparent Power (S) 
Voltage Rating 
Current Rating 
Frequency 
Power factor 
3) The calculation of the XU = XV = XW and RU = RV = RW actual values, i.e. the conversion from the perunit values.
4) The calculation of the perphase load impedance of the Yconnected load (Refer to Class Example 2) for both the X = XL and X = XC cases. How does ZY for X = XL differ from ZY for X = XC and why?
Phase current: I_{1p} = I_{1L}, I_{2p} = I_{2L}, I_{3p} = I_{3L}
Line current: I_{L} = I_{1L} = I_{2L} = I_{3L }
Phase voltage:
Line voltage: V_{L} = V_{12} = V_{23} = V_{31}
For X = XL
The per phase impedance remains the same in start connected circuit no conversion is needed so for the both cases it can be written as
5) The computation of the perphase load impedance of an equivalent Δconnected load
The equivalent impedance is given as
As its balance load circuit all impedance are same so the per phase equivalent impedance is give as
6) From the measurements, determine the mathematical relationship between the magnitudes of the line voltage and linetoneutral voltage for phase a. Does it agree with the theoretical principles?
According to readings
References:
[1] Louis, M.M., 2014. Elements of Electrical Engineering. PHI Learning Pvt. Ltd.
[2] Dorf, R.C., 2018. Pocket book of electrical engineering formulas. CRC Press.
[3] Bird, J., 2017. Electrical circuit theory and technology. Routledge.
[4] Mayergoyz, I.D. and Lawson, W., 1997. Basic electric circuit theory: a onesemester text. Gulf Professional Publishing.
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