Conventional magnet couplings which have been applied to productive machines of medicine and food-stuff are small power (10N•m-1, 200rpm). Recently, the magnet couplings of large power (high speed and large torque) are required for a fluid pump for oil and an apparatus of laser. Rareearth permanent magnets (Sm-Co, Nd-Fe-B) with high energy products allow us to develop the large permanent magnet coupling.
The small magnet coupling was developed by the way of trial and error or the macroscopic torque analysis. But it is difficult to design the large magnet coupling without the analysis of high accuracy. A finite element method makes it possible to analyze magnetic field with accuracy.
This paper presents the torque analysis of the large parmanent magnet coupling. The analysis is composed of two dimensional magnetostatic finite element method and the calculation, which compensates the decrease of torque by leakage flux at axial ends. We analyzed the large permanent magnet coupling with the rated power of 100N•m-8, 000rpm. Then, we measured the torque of the magnet coupling which was made of Sm-Co permanent magnet.
The analysis shows good agreements with test results within the error of few percent.
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