Question

d) Consider an ideal, single-phase 2400V-240V transformer. The primary is connected to a 2200V source and the secondary is connected to an impedance of 2Ω ∠36.9o , find all the values in Table 1.

Table 1

No	Parameters
1	The secondary output current and voltage.
2	The primary input current
3	The load impedance as seen from the primary side.
4	The input and output apparent power
5	The output power factor

e) A 30MVA 33/11 kV star-delta three phase transformer is installed in one of the Main Intake Substation Swiss Power Company. Determine the transformer rating in terms of voltage, current and turns ratio. If the chief engineer decided to use a new transformer with 30MVA 33/11 kV delta-star connection, determine the new ratings. (15 marks)

Lampiran 1/ Appendix 1 BT) 1.6 Sheet steel Case sieci 14 12 10 08 BI Cast iron 0.6 04 02 . 0 HAVm) A 500 1000 1500 2000 2500 2000 3500 4000 4500 5000

Answer 1

di Secondary voltage V2 - 240 Vaated but tum ratio N 2400 duo Ne -10. cy primary V- 2200 V SO V2 = 2200 x - 220V load 1. Na N ZL 202_36:9 Seconday output current I Iz 220LO V2 zi 110 L-36.99 2 (36.99 1, -HO A Primary input current 1 - I zx 7 ј0 x = ! A 3 load impedance seen from primay Zro u 2_c1) 2 [36.** (10)". poo [3632 input apparent power S, = VI S: - 2900 x 11. - 24200 VA S, -84.2 kVA as input VA = Output VA S2 = 84,2 AVA: de power factor cosøen.cos 36.9° = 0.8 Clag) CS Scanned with ÇamScanner 24.2 VA 5.