(7-11)
The general equivalent circuit for the Synchronous Machine is as shown in Figure 8-1. A second damper winding on the q-axis is included in this model and hence, it can also be used as a round rotor machine to model steam turbine generators. This model is particularly suitable for studying sub-synchronous resonance (SSR) problems as well.
This model operates in the generator mode so that a positive real power indicates electrical power leaving the machine, and a positive mechanical torque indicates mechanical power entering the machine. A positive reactive power indicates the machine is supplying reactive power (i.e. overexcited).
The ability exists to either control the speed directly or to input the mechanical torque, and calculate the speed from Equation 7-10.
Referring to Figures 8-2 and 8-3, the d-axis voltage UD2 and current ID2 are the field voltage and current, respectively. The damper circuit consists of parameters L3D and R3D with UD3 =0. The additional inductance L23D accounts for the mutual flux, which links only the damper and field windings and not the stator winding. The inclusion of such flux, necessary for accurate representation of transient currents in the rotor circuits, is illustrated in [14]. Only the saturation of LMD is considered in this machine and is based on the magnetizing current,
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(7-11) |
The matrix 
is recalculated each time there is a significant change in the saturation factor.