EET-226 Lecture Notes - Lecture 14: Kcna2, Volt-Ampere, Ac Power
Document Summary
A farm grain drying, and storage center is supplied with a 277/480-v, 3 phase system. 20 -a, 120-v circuits are required for lights and receptacle outlets. Determine the maximum kva rating of the single-phase, 480-v step-down transformer. = (120 v) * (40 a) = 4800 va. A single-phase transformer rated 7. 2 kva, 1. 2 kv/120 v has a primary winding of 800 turns. Determine: the turns ratio and the number of turns in the secondary winding. 96000/1. 2 kv = ns*1. 2 kv/1. 2 kv (1. 2 kv cancels out each other) 96000/1200 v = (80 t) = ns: s = 7. 2 kva. 800 (np)/80 (ns) = 10: the currents carried by the two windings when the transformer delivers its rated kva at rated voltages. A doorbell requires 0. 4 a at 6 v. it is connected to a transformer whose primary coil has a. X= np/ns = vp/vs = 110 v/6 v = 18. 33. P = v*i cos0 (6 v) *(0. 4 a) *1.
