Tham khảo tài liệu '(mcgraw-hill) (instructors manual) electric machinery fundamentals 4th edition episode 1 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | V vL f-y V V S a The voltage regulation is VR 7967 8573 x 1 0 8573 2-7. A 5000-kVA 230 single-phase power transformer has a per-unit resistance of 1 percent and a perunit reactance of 5 percent data taken from the transformer s nameplate . The open-circuit test performed on the low-voltage side of the transformer yielded the following data VOC kV IOC A POC kW a Find the equivalent circuit referred to the low-voltage side of this transformer. b If the voltage on the secondary side is kV and the power supplied is 4000 kW at PF lagging find the voltage regulation of the transformer. Find its efficiency. Solution a The open-circuit test was performed on the low-voltage side of the transformer so it can be used to directly find the components of the excitation branch relative to the low-voltage side. T G - jB I5 1 A 1 1 1 C M kV P e cos- pOC V I oc oc cos J kV A Tex GC - jBM - s - s RC A- 4240 Q Xm bF 936 Q The base impedance of this transformer referred to the secondary side is V 2 7 __ base base Sbase kV 2 5000 kVA Q so Req Q Q and XEQ Q Q. The resulting equivalent circuit is shown below 35 Req s Q X EQ s Q RC 4240 Q XMs 936 Q C s W2 s b If the load on the secondary side of the transformer is 4000 kW at PF lagging and the secondary voltage is kV the secondary current is Is . 000 Zot A S VS PF kV IS A The voltage on the primary side of the transformer referred to the secondary side is V V T 7 P S S EQ V 13 800Z0 V A Q 14 V There is a voltage drop of 14 V under these load conditions. Therefore the voltage regulation of the transformer is VR 14 330 -13 800 X 100 13 800 The transformer copper losses and core losses are PCU IS2 Req s A 2 Q kW P_ core K 1 Rc 14 330 V 2 4240 Q kW Therefore the efficiency of .
