AC Distribution System:
AC Distribution Calculations : AC Distribution Calculations differ from those of d.c. distribution in the following respects : In case of d.c. system, the voltage drop is due to resistance alone. However, in a.c. system, the voltage drops are due to the combined effects of resistance, inductance and capacitance. In a d.c. system, additions and subtractions of currents or voltages are done arithmetically but in case of a.c. system, these operations are done vectorially. In an a.c. system, power factor (p.f.) has to be taken into account. Loads tapped off form the distributor are generally at different power factors. There are two ways of referring power factor viz It may be referred to supply or receiving end voltage which is regarded as the reference It may be referred to the voltage at the load point itself. There are several ways of solving AC Distribution Calculations. However, symbolic notation method has been found to be most convenient for this purpose. In this method, voltages, currents and impedances are expressed in complex notation and the calculations are made exactly as …
Three Phase Unbalanced Load : The 3-phase loads that have the same impedance and power factor in each phase are called balanced loads. The problems on balanced loads can be solved by considering one phase only ; the conditions in the other two phases being similar. However, we may come across a situation when loads are unbalanced i.e. each load phase has different impedance and/or power factor. In that case, current and power in each phase will be different. In practice, we may come across the following Three Phase Unbalanced Load : Four-wire star-connected unbalanced load Unbalanced Δ connected load Unbalanced 3-wire, Y-connected load The 3-phase, 4-wire system is widely used is connected between any line and neutral wire while a 3-phase load is connected across the three lines. The 3-phase, 4-wire system invariably carries unbalanced loads. In this chapter, we shall only discuss this type of Three Phase Unbalanced Load. Four-Wire Star-Connected Unbalanced Loads: We can obtain this type of load in two ways. First, we may connect a 3-phase, 4-wire unbalanced load to a 3-phase, 4-wire supply …
