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What is meant by RLC?
What is meant by RLC?
In an RLC circuit, the most fundamental elements of a resistor, inductor, and capacitor are connected across a voltage supply. All of these elements are linear and passive in nature. Passive components are ones that consume energy rather than producing it; linear elements are those which have a linear relationship between voltage and current.
RLC circuit is an electrical circuit consisting of the followings:
a resistor (R)
an inductor (L)
a capacitor (C),
The RLC circuit can be connected in series or parallel.
1. Resistive circuit
Loads or equipment under resistive circuit:
heating element
DC component
electronics or semi-conductor related
Resistance Formula;
R ( Ω ) = V ÷ I or V² ÷ P
2. Inductive circuit
Loads or equipment under this circuit:
electric motor
discharge lamps
transformer
The unit for inductive is ' H ' or ' Henry ' and symbol is 'L '
Inductive reactance formula;
XL ( Ω ) = 2 x π x Freq x L
3. Capacitive circuit
Loads or equipment under this circuit:
Uninterrupted power supply unit (for Computer)
equipment with capacitors added to the circuits
The unit for capacitive is 'Farad ' or 'F '.
Capacitive reactance formula;
XC ( Ω ) = 1 ÷ ( 2 x π x Freq x C )
RLC connected in series
RLC connected in series
Figure above showing RLC are connected in series (or single line).
Since all these components are connected in series, the current in each element remains the same,
IR = IXL = I XcLet VR be the voltage across resistor, R.
VL be the voltage across inductor, L.
VC be the voltage across capacitor, C.
XL be the inductive reactance.
XC be the capacitive reactance.
Figure above is where capacitor is connected to store charge and improve power factor.
The Terms
The Terms
In-phase - means the voltage and current is same direction with wave.
Out of phase - means the voltage and current is shifted by an angle and not rotating not same direction with wave.
Leading - means the current or voltage is leading one another by an angle.
Lagging - means the current or voltage is lagging from one another by an angle.
The voltage across the capacitor c that is Vc is drawn lagging the current I by a 90° angle because in capacitive load the current leads the voltage by an angle of 90° . The two vector VL and VC are opposite to each other.
Phasor Diagram
Phasor Diagram
A phasor is a vector that has an arrow head at one end which signifies partly the maximum value of the vector quantity ( V or I ) and partly the end of the vector that rotates.
Refer to figure below.
RLC connected in parallel
RLC connected in parallel
In parallel RLC Circuit the resistor, inductor and capacitor are connected in parallel across a voltage supply. The parallel RLC circuit is exactly opposite to the series RLC circuit. The applied voltage remains the same across all components and the supply current gets divided.
The total current drawn from the supply is not equal to mathematical sum of the current flowing in the individual component, but it is equal to its vector sum of all the currents, as the current flowing in resistor, inductor and capacitor are not in the same phase with each other; so they cannot be added arithmetically.
The current through each element can be found using Kirchhoff’s Current Law, which states that the sum of currents entering a junction or node is equal to the sum of current leaving that node.
Figure above are the all components of R,L,C together in parallel.
In the parallel RLC circuit, all the components are connected in parallel; so the voltage across each element is same. Therefore, for drawing phasor diagram, take voltage as reference vector and all the other currents IR, IC, IL are drawn relative to this voltage vector.
Impedance Z
Impedance Z
The impedance Z of a series RLC circuit is defined as opposition to the flow of current due circuit resistance R, inductive reactance, XL and capacitive reactance, XC. If the inductive reactance is greater than the capacitive reactance (XL > XC ) then the RLC circuit has lagging phase angle and if the capacitive reactance is greater than the inductive reactance( XC > XL ) then, the RLC circuit have leading phase angle and if both inductive and capacitive are same ( XL = XC ) then circuit will behave as purely resistive circuit.
Impedance Formula
What is resonance ?
What is resonance ?
In a circuit containing inductor and capacitor, the energy is stored in two different ways.
1. When a current flows in a inductor, energy is stored in magnetic field.
2. When a capacitor is charged, energy is stored in static electric field.
The magnetic field in the inductor is built by the current, which gets provided by the discharging capacitor. Similarly, the capacitor is charged by the current produced by collapsing magnetic field of inductor and this process continues on and on, causing electrical energy to oscillate between the magnetic field and the electric field. In some cases at certain a certain frequency known as the resonant frequency, the inductive reactance of the circuit becomes equal to capacitive reactance which causes the electrical energy to oscillate between the electric field of the capacitor and magnetic field of the inductor.
When resonance occurs, the inductive reactance of the circuit becomes equal to capacitive reactance, which causes the circuit impedance to be minimum in case of series RLC circuit; but when resistor, inductor and capacitor are connected in parallel, the circuit impedance becomes maximum, so the parallel RLC circuit is sometimes called as anti-resonator.
Example calculation
Example calculation
Given an inductive load 0.8 H is connected to AC supply source with 50 hert frequency, find inductive reactance XL?
Three components RLC are connected in series with each following value of R=25 ohm, XL = 56 ohm and Xc = 18 ohm, find the impedance, Z ?
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