## THREE PHASE SYSTEM

At the end of this week, the students are expected to: Define polyphase system Explain the basic differences between single phase and three phase systems Explain phase sequence of a three phase system State the advantages of three phase circuits. POLYPHASE SYSTEM Circuits or system in which the ac sources operate at the same frequency…

## POWER IN A.C CIRCUIT

At the end of this week, the students are expected to: Calculate power in a.c circuits containing: Resistance Inductance Capacitance Combination of the resistance, inductance and capacitance 1.1 POWER IN A.C CIRCUIT 1.1.1 Power in A.C circuit containing Resistance only + Fig 1.1: (a) pure resistive circuit, (b) power wave form. (b) Inspection of the…

## APPARENT POWER, REACTIVE POWER AND ACTIVE POWER/POWER IN A.C CIRCUIT

Fig 1.9: Apparent power S = VI When a load has voltage V across it and current I through it as in figure 1.9, the power that appears to flow to it is VI. However, if the load contains both resistance and reactance, this product represents neither active power nor reactive power. Since VI appears…

## APPARENT POWER, REACTIVE POWER AND ACTIVE POWER/POWER IN A.C CIRCUIT

Fig 1.9: Apparent power S = VI When a load has voltage V across it and current I through it as in figure 1.9, the power that appears to flow to it is VI. However, if the load contains both resistance and reactance, this product represents neither active power nor reactive power. Since VI appears…

## GENERATION OF THREE PHASE E.M.F’s

Three Phase Systems At the end of this week, the students are expected to: Explain how 3-phase e.m.fs are produced  Distinguish between star and delta three-phase system Derive the relationship between line and phase values of voltages and currents in a star and delta connected windings 2.5 GENERATION OF THREE PHASE E.M.F’s      …

## APPARENT POWER, REACTIVE POWER AND ACTIVE POWER/POWER IN A.C CIRCUIT

Fig 1.9: Apparent power S = VI When a load has voltage V across it and current I through it as in figure 1.9, the power that appears to flow to it is VI. However, if the load contains both resistance and reactance, this product represents neither active power nor reactive power. Since VI appears…

## ESSENCE OF CONNECTING A RESISTOR IN PARALLEL WITH AN INDUCTOR

Fig 3.9: Decay of current in an RL series circuit Let us consider the circuit shown in figure 3.9. A discharge resistor RD is connected in parallel with the inductive circuit. When the switch S is connected to A, the current  becomes E/R. When the switch is moved to position B, the circuit is disconnected from…

## POWER FACTOR AND FACTORS AFFECTING ITS VALUE /POWER IN A.C CIRCUIT

Power Factor Power factor is the ratio of the real power dissipated in the load to the apparent power of the load. Thus, P.f = cosθ = P/S (1.4) Angle θ is the angle between voltage and current. For a pure resistance, therefore, θ =00. 0; for a pure capacitance, θ = -900. For a…

## DERIVATION FOR POWER IN A 3-PHASE CIRCUIT (BALANCED AND UNBALANCED)

At the end of this week, the students are expected to: – Derive an expression for power in a three-phase circuit (balanced and unbalanced) – Explain the two wattmeter and single wattmeter methods of measuring three-phase power 2.8 DERIVATION FOR POWER IN A 3-PHASE CIRCUIT (BALANCED AND UNBALANCED) 2.8.1 Power in a 3-Phase circuit (balanced-delta connection)…