Abstract: The spindle flux, as the sole medium for the electromechanical energy conversion in the high speed motorized spindle, is a significant factor in the high speed motorized spindle design and control, because the degree of spindle output torque and speed difference are determined by the degree and stability of flux when the high speed motorized spindle is running. In order to maintain a constant high speed motorized spindle flux, the causes of flux weakening when the spindle is operated in the Uf control mode with low frequencies are discussed, based on the thought of equivalent circuit of high speed spindle and the principle of frequency control, thus the voltage compensation formula is put forward with the aim to keep constant flux; on this basis, the electromagnetic torque is linked with the spindle speed difference through the slip frequency, and the relationship among the speed difference, the electromagnetic torque and the stator current is deduced, which is used to judge whether the spindle flux is stable or not. The results show that the spindles capacity of output torque is not affected by frequency changes when the spindle voltage is compensated in the Uf control mode, and that the judgment of flux stability through no-load current is consistent with the theoretical analysis. The influence of the spindle speed on radial runout directly reflects the degree of flux fluctuation, the torque control precision, and the balancing characteristic of the spindle in the operating process.

Key words: Dynamic response, Frequency control, High-speed motorized spindle, Magnetic flux, Torque control