Couplings are power transmission on structural connection device each other between primary part and secondary part. Generally, mechanical couplings are widely used in various applications. It is power transmission by mechanical contact each other. So, it is absolutely necessary maintenance in order to prevent damage by contact. Also, when viewed from the equipment side, it is possible to become a cause of reducing the efficiency because there is a risk of damage during overload. Thus, in order to supplement drawback of mechanical couplings, this paper deals with study for non-contact type magnetic couplings using magnetic force.
Contrary to mechanical couplings, magnetic couplings (MCs) can transmit power from the primary side to the secondary side without any mechanical contact. Because, it can transmit energy when the magnets are magnetically coupled to one another. In comparison with mechanical couplings, MCs can minimize noise and vibration during power transmission, so it can transmit the energy through a separate wall or space, suitable for use in a hazardous environment or isolated system. For example, the linear generator of a wave-energy converter that uses resonance power buoys must be set up a watertight container because electrical and mechanical problems may be caused by the inflow of seawater. Thus, the permanent magnet (PM) linear magnetic coupling that transfers energy through a structural connection with a linear generator performing linear motion under the water surface can effectively prevent the inflow of seawater, so this problem mentioned above can be solved. At the same time, if excessive force is applied during transmission, slip occurs the devices at both ends ; this helps prevent mechanical damage, it can reduce the maintenance costs. For this reason, MCs are an effective machine which can substitute for mechanical couplings.
Moreover, rare-earth materials such as SmCo or NdFeB used in PM couplings because energy density and intensity of magnetic field are much higher. Thus, it can obtain a much higher efficiency and force / torque density than the conventional permanent magnet. Also, it can be compact and lightweight, so it is easy to optimize in terms of machine design.
Couplings using PM are comprised of four types : Radial, Axial, Tubular, Linear coupling. Radial type coupling is difficult to manufacture of PMs, Axial type coupling is essential 3D analysis because of the geometric structure characteristic. It need to consume a lot of analysis time.
Thus, this paper deals with the linear coupling with a simple structure. Usually, linear machine is highly suitable for a place that requires a linear motion. In addition, in comparison with rotary type they can be used to a place where noise and vibration are small, reduced maintenance costs, an accurate position control because it not need to convert the rotational motion.
The measures to analyze a permanent magnet machine, there are analytical methods based on electromagnetic theory, such as the Maxwell equations. Firstly, a finite element analysis (FEA) is a kind of numerical methods. Secondly, a space harmonic methods is a kind of analytical methods. FEA is a program that is used to verify the analytical results, it is frequently utilized in commercial programs with high accuracy and reliability. However, it is need to perform a 3D analysis that is time-consuming for the complex structure analysis. On the other hand, analytical method has advantage that can obtain the desired result by modifying the design parameters according to need with a short analysis time.
Therefore, this study deals with the characteristic analysis of double-sided PM linear magnetic coupling with vertical magnetized based on an analytical method. To verify the accuracy and reliability of the study, it is performed force characteristic based on the magnetic flux density result in comparison with the FEA. Accordingly, various analysis results can obtain through these processes. Analytical method indicated in this paper can be useful to initial design of PM linear magnetic coupling with vertical magnetized.