Tham khảo tài liệu '(mcgraw-hill) (instructors manual) electric machinery fundamentals 4th edition episode 1 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | a This generator is Y-connected so IL IA. At rated conditions the line and phase current in this generator is IA IL i 7000 kVA 251 A at an angle of L 73 VL 73 2300 V The phase voltage of this machine is Vộ VT 73 1328 V. The internal generated voltage of the machine is E A V RaIA jX SIA A y A A SA Ea 1328Z0 Q 251Z- A j Q A Ea V The input power to this generator is equal to the output power plus losses. The rated output power is POUT 1000 kVA 800 kW PCU 3Ia2 Ra 3 251 A 2 Q kW Pf w 24 kW Pcore 18 kW Pstray assumed 0 Pin Pout Pcu Pf w Pcore Pstray kW n -A X100 800 kW X100 PIN kW b If the generator is loaded to rated kVA with lagging loads the phase voltage is V 1328Z0 V and the internal generated voltage is EA V . Therefore the phase voltage at no-load would be V 1537Z0 V . The voltage regulation would be VR 1537 1328 X100 1328 c If the generator is loaded to rated kVA with leading loads the phase voltage is V 1328Z0 V and the internal generated voltage is E A V Rai A jX SIA A y A A SA Ea 1328Z0 Q A j Q A Ea V The voltage regulation would be VR 1217 1328 X100 1328 d If the generator is loaded to rated kVA at unity power factor the phase voltage is V 1328Z0 V and the internal generated voltage is E A V Rai A jX SIA A y A A SA 115 Ea 1328Z0 Q 251Z0 A j Q 251Z0 A Ea V The voltage regulation would be VR 1393 -1328 X100 1328 e For this problem we will assume that the terminal voltage is adjusted to 2300 V at no load conditions and see what happens to the voltage as load increases at lagging unity and leading power factors. Note that the maximum current will be 251 A in any case. A phasor diagram representing the situation at lagging power factor is shown below By the Pythagorean Theorem EA2 v RAIA cosớ X I sin ớ X I cosd-R L sin ớ 2 A p A A SA SA AS V JE2 - XSIA cos ớ - R 4 sin ớ 2 - R ỉ cos ớ - XSIA sin ớ p A SA
