The terms Y are known as Admitting Parameters, and
its unit of measure is the SIEMENS.
The parameters values can be calculated by making V1 = 0, that is,
short-circuited input port or V2 = 0, which means short-circuited output port. Therefore,
these parameters are known as Short Circuit Admittance Parameters.
We can define the parameters as:
a) Y11 ⇒ Short-circuit input admittance.
b) Y12 ⇒ Short-circuit transfer admittance from Port 2 to Port 1.
c) Y21 ⇒ Short-circuit transfer admittance from Port 1 to Port 2.
d) Y22 ⇒ Admittance of short-circuit output.
Therefore, if we want to calculate Y11 and Y21 we should connect
a current source I1to port 1 and short-circuit port 2. Thus,
determining the values of V1 e I2, together with the value of
I1 which we already know, we calculate the parameters.
And to calculate Y22 and Y12, we use the same reasoning,
connecting a current source I2 to port 2 and short-circuiting port 1.
As we know the value of I2 and calculating V1 and
I2, we can determine the parameters.
Similar to the Parameters Z , if Y12 = Y21 we say that the circuit is
PASSIVE or RECIPROCAL.
Thus, when a circuit is of this type, we can represent it by the circuit in the Figure 32-02.
If the circuit is not Reciprocal or Passive, that is, have dependent sources,
then we have to modify the model. See the Figure 32-03 an equivalent circuit model for general cases.
Note that this circuit is derived directly from the equations of the Parameters Y ,
given at the beginning of the page.
There is a relation between the parameters Y and Z given by the equations: