Question 3 A two-winding transformer rated at P = 90 kVA, V₁/VH=240/1200 V, f = 60 Hz. When this two-winding transformer operates at rated load and power factor pf = 0.8, its efficiency is 90%. (1) Calculate the primary currents on the low-voltage side ILv and high-voltage side IHV. (2) The above transformer is to be connected as an autotransformer, i) calculate the secondary current Isecondary of the autotransformer; ii) draw the relevant diagram and label all relevant currents and voltages if this transformer is to be used as a 1440/1200 V step-down autotransformer in a power distribution system. (3) Calculate the transformer kVA rating when used as an autotransformer. (For this part assume an ideal transformer.) (4) Calculate the total transformer loss Ploss when it operates at rated load and power factor pf = 0.8. (5) Calculate the efficiency n with the kVA loading of the part (1) and power factor pf = 0.8.
Load flow analysis
Load flow analysis is a study or numerical calculation of the power flow of power in steady-state conditions in any electrical system. It is used to determine the flow of power (real and reactive), voltage, or current in a system under any load conditions.
Nodal Matrix
The nodal matrix or simply known as admittance matrix, generally in engineering term it is called Y Matrix or Y bus, since it involve matrices so it is also referred as a n into n order matrix that represents a power system with n number of buses. It shows the buses' nodal admittance in a power system. The Y matrix is rather sparse in actual systems with thousands of buses. In the power system the transmission cables connect each bus to only a few other buses. Also the important data that one needs for have a power flow study is the Y Matrix.
Types of Buses
A bus is a type of system of communication that transfers data between the components inside a computer or between two or more computers. With multiple hardware connections, the earlier buses were parallel electrical wires but the term "bus" is now used for any type of physical arrangement which provides the same type of logical functions similar to the parallel electrical bus. Both parallel and bit connections are used by modern buses. They can be wired either electrical parallel or daisy chain topology or are connected by hubs which are switched same as in the case of Universal Serial Bus or USB.
Please answer the questions (4) and (5)
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