In the last lesson, the following points were described:
1.
How to compute the total impedance in parallel and seriesparallel circuits?
2.
How to solve for the current(s) in parallel and seriesparallel circuits, fed from single
phase ac supply, and then draw complete phasor diagram?
3.
How to find the power consumed in the circuits and also the different components,
and the power factor (lag/lead)?
In this lesson, the phenomenon of the resonance in series and parallel circuits, fed
from single phase variable frequency supply, is presented. Firstly, the conditions
necessary for resonance in the above circuits are derived. Then, the terms, such as
bandwidth and half power frequency, are described in detail. Some examples of the
resonance conditions in series and parallel circuits are presented in detail, along with the
respective phasor diagrams.
Keywords
: Resonance, bandwidth, half power frequency, series and parallel circuits,
After going through this lesson, the students will be able to answer the following
questions;
1.
How to derive the conditions for resonance in the series and parallel circuits, fed from
a single phase variable frequency supply?
2. How to compute the bandwidth and half power frequency, including power and
power factor under resonance condition, of the above circuits?
3. How to draw the complete phasor diagram under the resonance condition of the
above circuits, showing the currents and voltage drops in the different components?
Resonance in Series and Parallel Circuits
Series circuit
C
E
L
A
R
D
+

I
B
V
frequency
(f)
Fig. 17.1 (a) Circuit diagram.
The circuit, with resistance R, inductance L, and a capacitor, C in series (Fig. 17.1a) is
connected to a single phase variable frequency (
) supply.
f
The total impedance of the circuit is
Version 2 EE IIT, Kharagpur