Definition and Units of Admittance
– Admittance is a measure of how easily a circuit or device allows a current to flow.
– It is defined as the reciprocal of impedance.
– The SI unit of admittance is the siemens (S).
– The older unit of admittance is mho (℧).
– The term ‘admittance’ was coined by Oliver Heaviside in December 1887.
Relationship between Admittance and Impedance
– Admittance is the reciprocal of impedance.
– Impedance takes into account both resistance and reactance.
– Admittance considers the ease of current flow and dynamic effects of materials.
– Admittance is represented as Y = G + jB.
– G is the conductance measured in siemens, and B is the susceptance also measured in siemens.
Conversion from Impedance to Admittance
– Impedance (Z) is composed of real and imaginary parts (R and X).
– Admittance (Y) is the inverse of impedance (Y = Z^(-1)).
– Conductance (G) is the real part of admittance (G = R / (R^2 + X^2)).
– Susceptance (B) is the imaginary part of admittance (B = -X / (R^2 + X^2)).
– The magnitude and phase of admittance are given by |Y| and θ respectively.
Shunt Admittance in Electrical Power Systems Modeling
– Shunt admittance is used to model paths of least resistance in transformers and transmission lines.
– Shunt components in transformers model magnetizing current and core losses.
– Shunt components can be referenced to the primary or secondary side of transformers.
– When shunt components have significant effects on system operation, their admittance must be considered.
– Shunt admittance in transmission lines is governed by Y = yl, where y is the shunt admittance per unit length and l is the length of the line.
Other Related Concepts
– Nodal admittance matrix is a mathematical tool used in circuit analysis.
– Immittance is a general term that encompasses both impedance and admittance.
– There is a relationship between admittance and immittance matching in photonic crystals.
– SI electromagnetism units include admittance as a fundamental quantity.
– Equivalent-π representation is used to model long transmission lines. Source: https://en.wikipedia.org/wiki/Admittance
In electrical engineering, admittance is a measure of how easily a circuit or device will allow a current to flow. It is defined as the reciprocal of impedance, analogous to how conductance and resistance are defined. The SI unit of admittance is the siemens (symbol S); the older, synonymous unit is mho, and its symbol is ℧ (an upside-down uppercase omega Ω). Oliver Heaviside coined the term admittance in December 1887. Heaviside used Y to represent the magnitude of admittance, but it quickly became the conventional symbol for admittance itself through the publications of Charles Proteus Steinmetz. Heaviside probably chose Y simply because it is next to Z in the alphabet, the conventional symbol for impedance.
Admittance is defined as
where
Resistance is a measure of the opposition of a circuit to the flow of a steady current, while impedance takes into account not only the resistance but also dynamic effects (known as reactance). Likewise, admittance is not only a measure of the ease with which a steady current can flow, but also the dynamic effects of the material's susceptance to polarization:
where
- is the admittance, measured in siemens.
- is the conductance, measured in siemens.
- is the susceptance, measured in siemens.
The dynamic effects of the material's susceptance relate to the universal dielectric response, the power law scaling of a system's admittance with frequency under alternating current conditions.
