e+a Permanent magnet motor

This website gives a short overview of electrical machines used as permanent magnet motors and generators, their advantages and some application fields especially in the high speed domain. Here, a permanent magnet motor is supposed to be a synchronous machine with a magnetic excitation on the rotor, also known as brushless dc motor, PMSM or BLDC. The difference is, that latter one is typically fed with a rectangular current form whereas the first one is fed by a sinusoidal current form. The challenges of developing and manufacturing permanent magnet motors and generators are explained. With e+a located in Switzerland, there is a competent partner with more than 28 years of experience in designing and producing customized permanent magnet motor elements for various application areas.

Rotor of a permanent magnet motor with CFRP sleeve

Introduction 
Various requirements are actually leading to a growing demand for high speed permanent magnet motors and generators. First of all, the continuous need for an increased power density. Due to the quasi linear relation between rotational speed and shaft power of an electrical machine, increasing the rated speed is an effective way to boost power density and efficiency. Hence this approach takes advantage of increasing shaft power without changing the size of the machine. On the other hand, the same performance can be provided in a smaller volume. The latter is paramount in the field of machine tool applications for example. Thus spindles or the machine tool in a whole become smaller, weight is reduced and dynamical behavior is enhanced. Another point in this industry is the cycle time that a machine tool needs to complete a specific operation. The faster a tool can be moved and rotated the faster it is able to complete its task, not taking into account that high speed cutting operation rely on top speed to machine time efficiently respective parts.

Further interesting operation fields of high speed permanent magnet motors are applications where a standard gearbox is used to translate the rotational speed of conventional power grid frequency (50/60 Hz) driven motors to higher speed levels. A replacement of this gearbox and the related conventional motor with a speed controlled drive consisting of a high speed permanent magnet motor and a rectifier increases the overall efficiency and reduces the maintenance significantly.
The compressor industry is an example, where high efficiency, oil-free operation and no emissions make electric high speed permanent magnet motors the most environmental friendly compressor drives (For compressor applications, also asynchronous machines could be a good alternative due to its robustness). In the context of emission free application energy storage systems with high speed flywheels not only take advantage of high speed permanent magnet generators. Thus fossil generators with unwanted emissions can be avoided and maintenance costs can be reduced significantly. Cryo applications actually experience a very similar revolution of its drive technology. Directly driven motor elements replace a set of a gear box and a 50/60Hz standard motor. Efficiency can be increased, the needed space is by far downsized and maintenance costs are reduced. Hence energy recovery systems e.g. become more and more interesting from a financial and an ecological point of view. Thus permanent magnet motor elements contribute partly to the ongoing development of green energy applications. 

article from www.permanentmagnetmotor.org