Canned Motor Research Articles

Magnetic Thrust Bearing Operation and Industrial Pump Application

Magnetic bearings represent a new bearing technology, which has some advantages over conventional fluid film and wiling element bearings for some applications. The paper describes the basic concepts of magnetic thrust bearing operation involving the magnetic actuator, electronic controls, power amplifier, and sensor. The magnetic actuator is a magnetic circuit, which generates attractive forces. These support the rotating shaft. While it is often thought that magnetic bearings are highly nonlinear devices, this paper demonstrates that they are linear in both the perturbation flux and current when used in a double acting configuration. Electronic feedback controls are used to stabilize the bearing. Example design parameters are presented for an application to an industrial canned motor pump.

Electromagnetic Field Analysis of Canned Motor for Hermetic Compressor using 2D Finite Element Method Combined with 3D Method.

Owing to the regulation of Freon gas in environmental problem, ammonia is recently revalued as refrigerant of compressors. A canned motor was developed as a reliable driver of a hermetic-type ammonia compressor. The canned motor has a thin, metallic can inserted in the airgap of a squirrel-cage induction motor to prevent ammonia from entering the stator and damaging the primary windings.As the can is conductive, eddy current and electromagnetic force are generated in it. To know these phenomena correctly, the finite element analysis is necessary because the equivalent circuit approach is inadequate. As end positions of the can have strong effect on eddy current in the can, a 3D analysis is needed to calculate electric field accurately. Furthermore, a nonlinear analysis with fine mesh in the airgap is required to calculate electromagnetic force distribution. In this case, large amount of computer memory and calculation time will be needed if a full 3D analysis is carried out.In this paper, we present a nonlinear 2D analysis combined with 3D analysis which can calculate both eddy current and electromagnetic force distributions accurately with small computer resources.The analytical results show the good agreement with experimental data. Moreover, we obtain new information which is instructive for the design of canned motors.

Major design parameters of a solid canned permanent magnet motor with skewed magnets

Permanent magnets buried in the rotors of synchronous machines are now accepted as a means of producing a high performance machine which can take advantage of rare earth magnets. The magnets can with advantage be nonradial, but an alternative strategy is to use radial magnets with a significant skew. It will be seen that this arrangement leads to a drastic reduction in harmonics and cogging torques. The use of a supporting tube on the rotor whether magnetic or not, is also investigated with a view to overcoming problems of high-speed operation.

Magneto-thermal coupled analysis of canned induction motor

The authors present the calculation of the distribution of the transient temperature in the rotor bars of a canned induction motor, during locked rotor conditions, where the phenomena of electromagnetically induced currents and heat transfer are coupled. They have developed a coupled finite element electromagnetic code called WEMAP in which the calculated power loss densities are used as the heat sources for a transient thermal solution in subregions of the original problem geometry. These subregions are enclosed by surfaces on which either temperature or a convection boundary condition is known. In addition, the change in rotor bar resistance as a function of the temperature is included in these calculations. The calculated temperatures are compared with test results, and favorable agreement is obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An analysis of the effect of journal bearings with helical grooves on the stability of a vertically mounted canned motor pump

An analysis of a vibration problem encountered on a vertically mounted, canned motor pump is described. Details are given of the flush water lubrication system and the two laminated pf resin journal bearings with helical grooves. The vibrational behaviour is described and attributed to bearing instability. A stability analysis based upon a finite element model of the rotor and finite difference solution to the bearing equations is discussed. Particular emphasis is given to the data available and the assumptions that had to be made. The role of the circumferential supply pressure in influencing stability id highlighted and the effect on stability and lubricant axial flow rate of the start of the start position and number of helical grooves is demonstrated. The effect of increased bearing clearance is also discussed. A recommendation to replace the single groove by a bearing with two grooves for the upper bearing is the main conclusion

Paper 9: Canned Motor Pump Design

The canned motor pump principle, its design and analysis techniques, as well as some manufacturing problems and problem analyses, are outlined in this paper. Types of operations that might have severe adverse effects on the life of the unit are also discussed. Particular attention is given to the detailed analytical evaluations of the design as to methods and criteria used in the thermal and stress analyses. Special emphasis is given to can fatigue evaluation in general, with descriptions of a successful design solution.

Calcification of pericardium: Drummond, C. I.: Northwest Med. 39: 217, 1940

Sealless pumps can be found in many process applications and today both canned motor and magnetic drive pumps come in a wide range of sizes, with multiple hydraulic and drive configurations available in a variety of materials. In a look at how this technology has evolved Mitchell H. Rosenbaum and Stephen A. Jaskiewicz explain why sealless pumps are unique to most process pumps.