# Polyphase Circuits

## Effects of Harmonics

Effects of Harmonics: The relationship between line and phase quantities for wye and delta connections as derived earlier are strictly valid only if the source voltage is purely sinusoidal. Such a waveform is an ideal one. Modern alternations are designed to give a terminal voltage which is almost sinusoidal. But it is nearly impossible to …

## Reactive Power with Wattmeter

Reactive Power with Wattmeter: We have already seen earlier that the difference between higher reading wattmeter and lower reading wattmeter yields VLIL sin Φ. So, the total reactive power = √3 VLIL sin Φ. Reactive Power with Wattmeter in a balanced three-phase load can also be calculated by using a single wattmeter. As shown in …

Leading Power Factor Load: Suppose the load in Fig. 9.46(a) is capacitive, the wattmeter connected in the leading phase would read less value. In that case, WR will be the lower reading wattmeter, and WY will be the higher reading wattmeter. Figure 9.48 shows the phasor diagram for the Leading Power Factor Load. As the …

## Power Factor by Two Wattmeter Method

Power Factor by Two Wattmeter Method: When we talk about the power factor in three-phase circuits, it applies only to balanced circuits, since the power factor in a balanced load is the power factor of any phase. We cannot strictly define the power factor in three-phase unbalanced circuits, as every phase has a separate power …

## Three Wattmeter and Two Wattmeter Method

Three Wattmeter and Two Wattmeter Method: In this method, the three wattmeter are connected in the three lines as shown in Fig. 9.45, i.e. the current coils of the three wattmeter are introduced in the three lines, and one terminal of each potential coil is connected to one terminal of the corresponding current coil, the …

## Power in Three Phase Circuits

Power in Three Phase Circuits: Measurement of power by a wattmeter in a single phase circuit can be extended to measure Power in Three Phase Circuits. From earlier Section, it is clear that we require three wattmeters, one in each phase to measure the power consumed in a three-phase system. Obviously, the total power is …

## Power Measurement in Single Phase Circuit by Wattmeter

Power Measurement in Single Phase Circuit by Wattmeter: Wattmeters are generally used to measure power in the circuits. A wattmeter principally consists of two coils, one coil is called the current coil, and the other the pressure or voltage coil. A diagrammatic representation of a wattmeter connected to measure power in a single phase circuit …

## Unbalanced Three Phase Circuit Analysis

Unbalanced Three Phase Circuit Analysis: Types of Unbalanced Loads – An unbalance exists in a circuit when the impedances in one or more phases differ from the impedances of the other phases. In such a case, line or phase currents are different and are displaced from one another by unequal angles. So far, we have …

## Three Phase Balanced Circuit

Three Phase Balanced Circuit: The analysis of Three Phase Balanced Circuit is presented in this section. It is no way different from the analysis of AC systems in general. The relation between voltages, currents and power in delta-connected and star-connected systems has already been discussed in earlier section. Balanced Three-Phase System-Delta Load: Figure 9.31(a) shows …

## 3 Phase Delta Connection

3 Phase Delta Connection: Delta Connected System – Figure 9.26 shows a balanced three-phase, three-wire, delta-connected system. This arrangement is referred to as mesh connection because it forms a closed circuit. It is also known as 3 Phase Delta Connection because the three branches in the circuit can also be arranged in the shape of …