電機機械題目講解 老師 : 秦純 學號 :MA 學生 : 蔡景棠

4.20 A four-pole, 60Hz synchronous generators has a rotor length of 5.2 m, diameter of 1.24 m, and air-gap length of 5.9 cm. The rotor winding consists of a series connection of 63 turns per pole with a winding factor of Kr = The peak values of the fundamental air-gap flux density is limited to 1.1 T and the rotor winding current to 2700 A. Calculate the maximum torque (N.m) and power output (MW) which can be supply by this machine. Ans: N-m

4.21 Thermal considerations limit the field-current of the laboratory-size synchronous generator of Problem 4.18 to a maximum value of 2.4A. If the peak fundamental air-gap flux density is limited to a maximum of 1.3T, calculate the maximum torque (N-m) and power (kW) which can be produced by this generator. Ans:

4.25 A three-phase linear ac motor has an armature winding of wavelength 25 cm. A three-phase balanced set of currents at a frequency of 100Hz is applied to the armature. a. Calculate the linear velocity of the armature mmf wave. b. For the case of a synchronous rotor, calculate the linear velocity of the rotor. c. For the case of an induction motor operating at a slip of 0.045, calculate the linear velocity of the rotor. Part(a) 25cm=0.25m m/sec Part(b) 同步轉子 速度 m/sec Part(c) =( ) 25= m/sec Ans:

4.26 The linear-motor armature of Problem 4.25 has a total active length of 7 wavelengths, with a total of 280 turns per phase with a winding factor kw = For and air-gap length of 0.93 cm, calculate the rms magnitude of the balanced three-phase currents which must be supplied to the armature to achieve a peak space-fundamental air-gap flux density of 1.45 T. Ans: 根據 4.88 式 得