Calculate the total voltage of the supply - NSC Electrical Technology Power Systems - Question 2 - 2019 - Paper 1

The inductive reactance ($X_L$) can be calculated using the formula:

X_L = rac{V_L}{I_T}

Given that $V_L = 16 V$ and $I_T = 3 A$:

X_L = rac{16}{3} \\ = 5.33 \, \Omega

The circuit is capacitive because the voltage drop across the capacitor ($V_C$) is greater than the voltage drop across the inductor ($V_L$). This indicates that the circuit has more capacitive effects than inductive, thereby contributing to the leading nature of the current.

To complete the phasor diagram:

• Draw the voltage vector for the resistor ($V_R = 12 V$) along the real axis.
• Draw the voltage vector for the inductor ($V_L = 16 V$) lagging behind $V_R$ by 90°.
• Draw the voltage vector for the capacitor ($V_C = 24 V$) leading $V_R$ by 90°.

The direction of rotation in this phasor diagram will show the result of the contributions from each of the elements in the circuit.

An increase in impedance ($Z$) while keeping the resistance ($R$) constant will lead to a decrease in the total current ($I_T$) flowing through the circuit. This will consequently increase the phase angle ($heta$). As the phase angle increases, the power factor ( ext{PF}) which is given by PF = rac{R}{Z} will decrease, indicating a less efficient circuit.