Issue 2(42), 2016


On the theory of calculating of radial active magnetic bearings pdf

I. L. Shchekleina, A. V. Ugol’nikov

This study reflects the advantages and problems of using the radial active magnetic bearing (AMB). I also describes the existing calculation methods. The traditional method of calculation (developer Yu. N. Zhuravlev) includes a definition of the geometry of the bearing, the calculation of the winding and thermal bearing calculation. To determine the geometry of the radial bearing authors used the optimization approach: the maximum driving force is realized in a given volume by the bearing. The starting point in the procedure of optimization of the geometry is the induction in the gap. It depends on the magnetic properties of the steel used. Unlike electrical machines, magnetic saturation in AMB is not allowed since it causes loss of control. Then authors calculate the bearing winding. Radial bearing has four electromagnets, so its winding contains four circuits. The coils may be included in the circuit either sequentially or parallel. Obviously, a parallel circuit requires higher current but lower voltage. Remagnetization losses on the rotor will be less if the magnetomotive
force (MMF) of two adjacent poles of adjacent magnets will have the same direction. Heat bearing calculation consists in determining the maximum temperature of the coil conductor and comparison with the allowable temperature for the used insulation class. The calculation bases on Ohm’s Law for steady heat flow. This method of calculation of the bearing has disadvantages; in result, you get the parameters at which the maximum driving force and the packet length may be more than is necessary. I. V. Zotov and V. G. Lisienko offered the methodology of calculating the bearing. It allows finding the minimum required length of the packet at the maximum electric current. Accordingly, the size and cost of the bearing reduce too. Analysis of the methods showed that it is necessary to improve the calculations in order to minimize the size and cost of the magnetic bearing. It is advisable to use these devices in the rotating parts of mining machines and complexes.

Keywords: bearing; electromagnet; method; calculation; tractive effort; magnetic circuit; electrical circuit; heat loss; heat flow; thermal resistance; insulation class.



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