If a simple potentiometer was connected to this input, it would allow manually-controlled PWM ratios to be produced, at frequencies set by R7 and C2. U1 completes the loop, amplifying the difference between the PWM input and an inverted copy of the output of U3...
In order to simplify the procedure, the switch, 𝑆𝑊𝑝SWp, was kept closed. The generator and switched-off reactor parameters were measured by using an Asita AS250 impedance meter (see Table 1). Mutual inductances in LTSpice were expressed by means of coefficient 𝐾K (Figure 12). ...