In fact there is not only a single trajectory circle to be measured. Fig. 6 shows that a synchronous machine with permanent magnets produces 2 circles with different diame- ters. When the HF voltage is injected in the same direction as the main field of the permanent magnets, the resulting field is slightly higher and results in a slightly higher saturation (showing a stator admittance circle with greater diameter) – when the HF voltage is injected in the opposite direction of the main field of the permanent magnets, the resulting field is slightly lower and results in a slightly lower saturation (showing a stator admittance circle with smaller diameter).