For the surge detection problem of high-speed magnetic suspension centrifugal blower, a second order generalized integral-frequency locked loop with prefilter (SOGI-FLL-WPF) is used for surge detection. This method is utilized to normalize the amplitude and frequency of the surge signal by using the rotor radial displacement signal in the magnetic suspension blower. So that the response speed of detecting surge signal is not affected by the frequency and amplitude, and the frequency of the blower surge vibration signal is tracked adaptively. As a result, the fast response ability of the surge signal detection is improved. Specifically, firstly, the rotor radial displacement signal is collected in real time. And then, the rotor speed is identified by SOGI-FLL, and the identified speed information is input to SOGI for notch. Finally, the surge detection is carried out by SOGI-FLL-WPF for the signal after notch. The 105 kW magnetic suspension centrifugal blower is applied for the surge detection experiment. The experimental results show that the surge detection method based on rotor radial displacement signal and SOGI-FLL-WPF can detect the surge signal immediately after its occurrence. The proposed detection method needs no additional detection unit, and has the advantages of simple algorithm, fast response speed and small amount of calculation. In addition, it can effectively reflect the change of frequency in the process of surge.

In the design process of a high-speed motor, a reasonable rotor stress analysis is a necessary prerequisite to guarantee its safe and reliable operation. In this paper, the comprehensive design and analysis of the rotor stress of a 200 kW 20,000 r/min high-speed permanent magnet motor (HSPMM) with magnetic bearing are carried out. Firstly, the stress distribution characteristics of rotors with different permanent magnet structures and different thermal expansion coefficients of filling materials are analyzed and compared. Secondly, the rotor design is determined through a comprehensive comparative analysis of different sleeve thicknesses and shrink fit. Furthermore, considering the axial temperature gradient due to the axial ventilation cooling method adopted by the prototype, the rotor stress is checked through the coupling calculation of fluent and static stress. Finally, several long-period running tests are carried out, showing the good agreement between the calculated and measured results, and the safe and reliable operation of the prototype verifies the correctness of the above theoretical analysis.

The impeller design usually expects to achieve high efficiency and a wide working range while they are influenced by tip clearance in different ways. In this study, a blower with a controllable magnetic suspension bearing was studied. The magnetic bearing enables the impeller to adjust the tip clearance during operation to optimize the efficiency of the blower at the design point and significantly expand the surge margin when it deviates from the design point. The clearance ratio (CR) is defined as the ratio of tip clearance over impeller outlet width. The computational fluid dynamics (CFD) method is used to study the performance of a centrifugal impeller under CR = 2.61%∼7.83% and verified by experiments. The results show that the pressure ratio and efficiency of the impeller at the design point decreased linearly with the increase of the gap. For each 1% increment in CR, the pressure ratio reduces by 0.02 and the polytropic compression efficiency declines by 0.5%. Conversely, the surge margin increases with the expansion of CR. For every 1% rise in CR, the surge margin would improve by 7.8%. A control method of changing the reference suspension position according to the optimal efficiency fitting model is proposed. It realizes the real-time control of the axial suspension position of the impeller according to the changes of pressure and flow rate signals to obtain the optimal work efficiency with a broad surge margin. Experimental results show that using an impeller equipped with a controllable magnetic suspension bearing could minimize the gap stably in the nonsurge area to obtain high efficiency, and when necessary, it could enlarge the gap to meet the low flow rate condition.

A surge detection method according to rotor axial displacement signal and normalized second-order generalized integrator-frequency locked loop-with prefilter (SOGI-FLL-WPF) is proposed to solve the surge detection problem of magnetic suspension fluid machinery, which has important practical significance. To improve the anti-disturbance performance of surge detection, SOGI is introduced as a prefilter. As a prefilter, SOGI can eliminate the interference in the surge signal, and normalized SOGI-FLL can estimate the amplitude and frequency of the surge signal. Normalized SOGI-FLL and prefilter are combined to form normalized SOGI-FLL-WPF. First, the disturbance transfer model between rotor axial displacement signal and pressure signal is deduced. Then, the surge is detected by normalized SOGI-FLL-WPF. This method has the merit of fast response, small computation, and good disturbance resistance without additional detection units. Finally, the test is implemented on 105 kW and 150 kW magnetic suspension blowers. The results demonstrate that the proposed method can quickly detect surge signal after the surge occurs.