Question

3. If the voltage and current (both are rms values) supplied to a circuit or load by a source are Varm) = 460?0° V, Is(m)-1414L-45° A. Determine the a) the power supplied by the source which is dissipated as heat or energy in the circuit, b) the power stored in the reactive components and c) the power factor angle and power factor 4. An ideal transformer is rated to deliver 460 KVA at 380 V to a customer T Customer's Load Ideal transformer Customer a) How much current can the transformer supply to the customer? b) If the customer's load is purely resistive (power factor, cos0 ), what is the maximum c) d) power that the customer can receive? If the customer's power factor is 0.8 (lagging) what is the maximum usable power that the customer can receive? What is the maximum power if the power factor (pf) is 0.7 (lagging)? If the customer requires 300kW to operate, what is the minimum power factor with the given size transformer? c)

Answer 1

V_s = 460 angle 0 I_s = 14.14 angle - 45 degree complex power 's' = v_s times I_x^* = 460 times 14.14 angle 45 = 4599/P(w) downarrow power dissipated (a) + j4599 downarrow Q(var) Reactive power (b) Power factor = cos 45 = 0.707 (lassing) (4) 460 kv A, downarrow VI, 380 v downarrow v (a) I = VI/V = 460 k/380- = 121.53 A (b) V I cos phi = 460 k times 1 = 460 kw (460 kw) (c) VI cos phi = 460 k times 0.8 = 368 kw (d) V I cos phi = 460 k times 0.7 = 322 kw (e) V I cos phi = 300 kw implies cos phi = 300 k/VI = 300 k/460 k implies four factor, cos phi = 0.652