Analytical approach and solution for start-up behavior of line-start permanent magnet synchronous machines (LSPSM)
This paper presents a derivation for the maximum transient current and torque peak values for small non-salient line starting permanent magnet synchronous machine (LSPSM) on base of permissible approximations. First the equations for locked rotor operation and secondly for constant speed operation are deduced. This paper is focused on derivation of the analytical calculation process to get an approach for transient current and torque. Saturation and speed dependency of parameters are not considered. With the derived equations, effects of parameters on the peak values of torque and current at starting can be shown.
Analytical Approach and Solution for Line-Start Permanent Magnet Synchronous Machines with Anisotropic Rotor Reluctance
In this paper the derivations of transient current and torque of a line start permanent magnet synchronous motor are described. Using the detailed analytical formulas, the dependencies of the current and torque on machine parameters and internal state quantities can be determined. This type of machines have an anisotropic rotor design and so the reluctance in direct axis and in quadrature axis have to be considered. For derivation the stator resistance and the initial angle of mains voltage are considered. The derived equations were validated due to a comparison with a numeric solution. Finally, the applicability of the derived torque as an approximation for the start-up is evaluated.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.