Analysis Of Loss And Research On New Method For Axial Force Balance In Canned Motor Pump

Canned motor pump has advantages completely leak-free, safe, reliable, low maintenance and low noise etc. However, because of its special structure, produced eddy current loss of can and axial force. Empirical formula calculated eddy current loss which has a big error, there are many assumptions, it is difficult to improve the efficiency of the canned motor and meet the engineering requirements. For the axial force balance, the traditional balance methods of balance hole, balance muscle and balance drum etc have some limitations, not balance the axial force real-time or dynamically, which causes bearings abnormal wear and tear, even lead canned motor can not work properly.Firstly, this paper reviews the development and application of canned motor pump, summarizes the structure, operating principles and design features of the canned motor. The calculating formula of eddy current loss of can and the calculating formula of frictional loss of rotor are referred. The paper designs two poles and 8kW canned motor.Secondly, this paper analyzes and calculates eddy current loss of can with ANSOFT, for different resistively material and different thickness. The paper develops four types of structure prototype with Hastelloy-C alloy or stainless steel Sus316L of the metal can and obtains the experimental value of eddy current loss of can via testing by the loss separation method. The results are compared with simulation, which gets to affect eddy current loss of can factors and proposes amendments to the empirical formula. The temperature field of the canned motor is analyzed to get the temperature rise value of can when the canned motor at the load and the start and calculate the corresponding thermal deformation.Finally, for the axial force problem, the paper proposes a new structure of permanent magnet axial force balance structure, its counterweight features are analyzed and calculated by using a numerical method of ANSOFT software, the result of counterweight features are validated via the experiment. Experiment shows that ANSOFT finite element software can be used as an effective way to design and calculate the new permanent magnet non-contact the axial force balance structure. For the rated power 8kW canned motor pump with a rated flow Q=30m~3/h, head H=35m, the effect of axial force balance is analyzed, appropriate axial force balance structure form and structural parameters are determined in the paper.