Question

A 1500 kW, unity pf, 3-phase, Y-connected, 2300 V-(line), 30 pole, 60 Hz synchronous motor has a synchronous reactance of 1.95 22/phase. For this problem all losses may be neglected. a. Compute the max. torque in Nm which this motor can deliver if it is supplied with power from an infinite bus, and if its field excitation is constant at the value which would result in unity (1.0) pf at rated load. b. Now, suppose that the motor is supplied from a 3-phase, Y-connected, 2300 V, 1750 kVA, 2-pole, 3600 rpm generator whose synchronous reactance is 2.65 2/phase. The field excitations of generator and motor are adjusted so that the motor runs at unity pf and rated terminal voltage at full- load. The field excitations of both machines are then held constant, and the mechanical load on the synchronous motor is gradually increased. Compute the max. motor torque under these conditions and the terminal voltage when the motor is delivering its max. torque.

Answer 1

may be A 15oukh, unity of, 3-phase Y - connected, 23000 ov-(line), 30 pole, 60Hz Synchronous motos has Synchownous reactance of 1.95 re/phase. For this problem all losses neglected a) Compute the max. torque which this motos Can delives if it is supplied with power from infinite bus, and if its field excitation constant at the value which would result i unity. (1.0) pf at rated load. m is . motos = 30 Step O: Power rating of the Synchronous motor, Pros: 1500kw Voltage supplied to the motos Vline = 2300 No. of poles of the Frequency supplied to the motor, f = 60 Hz. Synchronowe reactance of the motor , X₂ = 1.950/ph. Power of the load, coud Maximum tor que developed by the Imaxe = Synchownous motor factor 2 Condition for maximum powes developed by the motor (Pomach) man EV ale

E due to maximum power developed E = 2. coso 2800 = 1150 volte 2x (Pmech) man EV Xg 1150 x 2300 1.95 (Pman) 1.356M W Max Torque developed by the Synchronous motos (Prech) oraz 25 Nmax GO Tman Pmax x 60 2T Ns 120f 120x60 where Synchronous, Speed, Ns = Р = 240 rpm Tman 6 1,356x 10 x 60 2T X240 Maximum Torque developed by Tmax= 53.96K N-m the Synchronous motor