Design of a Test Bench for a Lateral Stator Electrical

In a previous study, lateral stator electrical machines have been proposed for micro-machining applications where the space in the tool head is limited. In this paper, the construction of a lateral stator machine merged into a test bench is described. The test bench is used for measuring the standstill torque of the machine in a configuration without bearings, such that only the electromagnetic torque is measured. Moreover, the test bench can be modified to measure the no-load losses and separate mechanical and electromagnetic components of it using a novel method. Further separation of different components of electromagnetic no-load losses is also discussed. Although described on a lateral stator machine, the methodology in this paper can be applied to any electrical machine. I. INTRODUCTION In the last few years, several studies dealing with design, optimization and testing of high-speed electrical drives have been published (1-11). In (12), the authors have grouped the application areas of those high-speed electrical drives into two groups: group of applications with one working point and group of applications where the drive needs to cover a wide torque-speed range. Turbo compressors are a good example of the first group whereas applications like micro-machining spindles belong to the second group. Furthermore, in (12), lateral stator electrical machines are proposed for the second group of applications in order to fit the motor in confined spaces around the rotor, while still maintaining the wide operating range. In the same paper, this wide operating range is characterized by two operating points: a low-speed high-torque operating point where all the high-speed losses such as the core losses in the stator and eddy current losses in the solid bodies are neglected; and a high-speed low-torque operating point, where the copper losses in the windings are neglected. The machine geometry is optimized using a parametric finite element method (FEM) simulation. In this paper, further considerations about building the lateral stator machine are described in detail. Moreover, the lateral stator machine is merged into a test bench which can evaluate the machine performance in the two operating points mentioned above, enabling a direct verification of the FEM simulations. This is done by modifying the test bench into two different setups, one measuring the torque at standstill, the other measuring the no-load losses at higher speeds. The first setup is called the static torque measurement setup and the second one is named as the high-speed loss measurement setup. In the static torque measurement setup, a bearingless configuration is designed, and the torque is measured on the stator side. This allows for the measurement of the electromagnetic torque only, without the bearing friction, which enables a direct verification of the FEM analysis. In the high-speed loss measurement setup, deceleration tests are used to measure the total no-load losses. A novel method of loss segregation is proposed which allows for the separation of the mechanical losses from the electromagnetic losses, overcoming the problem of changing bearing friction loss with changing preload. This is especially important with high-speed, low-torque electrical machines where bearing friction causes an important part of the no-load losses. Moreover, the segregation of the different components of the no-load losses is discussed. Although the test bench design is described for a special electrical machine type, the methodology can be used to test any other electrical machine in similar way.