A.C. Fundamentals - Susceptance-frequency curve
1 Answer
The Susceptance-frequency curve, also known as the B-f curve, is a graphical representation of how the susceptance (B) of a circuit component or network changes with respect to frequency. Susceptance is the imaginary part of the admittance and is denoted by the symbol B. It measures the reactance that is due to capacitive or inductive components in a circuit.
In an AC circuit, susceptance is given by the formula:
B = 1 / (Xc - XL)
Where:
B is the susceptance
Xc is the capacitive reactance (1 / (2πfC), where f is frequency and C is capacitance)
XL is the inductive reactance (2πfL, where f is frequency and L is inductance)
The susceptance-frequency curve is generally used to analyze circuits with both capacitive and inductive components. The curve shows how the total susceptance of the circuit changes as the frequency of the AC voltage source varies.
Here's what the curve typically looks like:
At very low frequencies (close to DC), the inductive reactance (XL) dominates, causing a positive value of susceptance. This is represented by a positive value of B on the curve.
As the frequency increases, the inductive reactance (XL) starts to decrease, causing the susceptance to decrease.
At a certain frequency, called the resonant frequency, the capacitive reactance (Xc) becomes equal to the inductive reactance (XL), resulting in zero net susceptance. This is the point where the curve crosses the zero susceptance line.
Beyond the resonant frequency, the capacitive reactance (Xc) becomes dominant, causing a negative value of susceptance. This is represented by a negative value of B on the curve.
As the frequency continues to increase, the absolute value of the capacitive reactance (Xc) increases, causing the absolute value of the susceptance to increase as well.
Remember that the susceptance-frequency curve is specific to circuits with both capacitive and inductive elements. Purely capacitive or purely inductive circuits would have different reactance-frequency behaviors. The curve helps engineers and technicians understand how different components in a circuit interact and how they affect the overall behavior of the circuit at different frequencies.
In an AC circuit, susceptance is given by the formula:
B = 1 / (Xc - XL)
Where:
B is the susceptance
Xc is the capacitive reactance (1 / (2πfC), where f is frequency and C is capacitance)
XL is the inductive reactance (2πfL, where f is frequency and L is inductance)
The susceptance-frequency curve is generally used to analyze circuits with both capacitive and inductive components. The curve shows how the total susceptance of the circuit changes as the frequency of the AC voltage source varies.
Here's what the curve typically looks like:
At very low frequencies (close to DC), the inductive reactance (XL) dominates, causing a positive value of susceptance. This is represented by a positive value of B on the curve.
As the frequency increases, the inductive reactance (XL) starts to decrease, causing the susceptance to decrease.
At a certain frequency, called the resonant frequency, the capacitive reactance (Xc) becomes equal to the inductive reactance (XL), resulting in zero net susceptance. This is the point where the curve crosses the zero susceptance line.
Beyond the resonant frequency, the capacitive reactance (Xc) becomes dominant, causing a negative value of susceptance. This is represented by a negative value of B on the curve.
As the frequency continues to increase, the absolute value of the capacitive reactance (Xc) increases, causing the absolute value of the susceptance to increase as well.
Remember that the susceptance-frequency curve is specific to circuits with both capacitive and inductive elements. Purely capacitive or purely inductive circuits would have different reactance-frequency behaviors. The curve helps engineers and technicians understand how different components in a circuit interact and how they affect the overall behavior of the circuit at different frequencies.