Discuss the methods used for finding the approximate

Question

Question 1:

a) Discuss the methods used for finding the approximate transformer parameters R_ser, L_ser, R_par, and L_par.

b) Explain what each of the parameters R_ser, L_ser, R_par, and L_par model and show their positions in the transformer's circuit diagram.

Following transformer testing on a 100 WA, 50 Hz, 1000 V:250 V step-down transformer, the following results table was compiled:

	Open-circuit test	Short-circuit test
Voltmeter reading (V)	1000	505
Ammeter reading (A)	2.5	7.2
Wattmeter reading (W)	105	88

c) From the transformer data and table determine the transformer's equivalent resistive parameters.

d) Likewise, determine the transformer's equivalent inductive parameters.

The transformer of (c) and (d) has an iron loss of 92 W and it is used on full-load with a power factor of one. What are the copper losses when its efficiencies are:

e) 98 %?

f) 84 %?

Question 2:

a) Electrical power generation and transmission requires electrical companies to charge tariff to cover costs and make profit. Discuss their capital and running charges.

An industrial unit utilising electrical machinery has a maximum demand of 250 kW, it has a power factor of 0.8 and a load factor of 0.35. Consider the following tariffs, and determine their annual (consider I year having 365 days) cost of electricity and their corresponding costing per kWh:

b) A maximum demand charge of £25/kW and a running charge of 5 p/kWh.

c) A maximum demand charge of £20/kVA and a running charge of 5 p/kWh

d) A basic maximum demand charge if £25/kW. This increases by a factor of 0.15 for each 0.1 the power factor is worse than 0.9. The running charge is 5 p/kWh.

e) Which tariff system would you recommend to the industrial unit?

Question 3:

a) Draw a schematic diagram of a per-phase synchronous electrical, generator.

b) Define the components in the armature (stator) side of the diagram

c) Define the generators torque components.

d) Define the enerators power components

A 3-phase, 600 WA synchronous generator has a rated line voltage of 3300 V. The stator winding is star connected and has a resistance of 0.37 Ω/phase Its synchronous impedance is 4.3 Ω/phase.

e) Draw the synchronous generator's per phase voltage and current phasor diagram.

f) Calculate the per phase output voltage.

g) Determine the voltage dropped across the synchronous impedance.

Calculate the synchronous generator's voltage regulation and output power for full loads having power factors of:

h) Unity.

I) 0.8 lagging.