In [22] Bolognani reported that the saturation in „q“ direc- tion increases under load (this effect is known as „armature reaction”) resulting in a variation of the ratio between the position depending HF inductances lcq and lcd . Under specif- ic conditions the inductances might be equal – the tracking control could not detect any difference any more. According to [22] this effect would disturb the encoderless control of synchronous motors with interior permanent magnets around 2 to 3 times rated load, whereas synchronous machines with surface mount permanent magnets show this effect later (around 5 to 6 times rated load).