$EVWUDFWThis paper presents a new rotor for permanent magnet wind generators aimed to reduce the amount of rare-earth materials. The new rotor configuration has been used for the design of a 10 MW PM generator for direct drive wind turbines in order to reduce their magnet costs. In order to prove its effectiveness, also a conventional PMSG with surface magnets rotor is considered as reference machine for comparison. Using the same geometry and electrical constrains the both PMSGs are developed following an analytical iterative procedure and afterwards using FEA. According to the preliminary results, the new rotor design requires significantly less magnet material compared with the conventional rotor. Investigations done on the 10 MW PMSG shows that with the proposed design the magnet weight can be reduced for about 2.7 tons. Index Terms-permanent magnet generator, new pm rotor configuration, rare earth material reduction, 10 MW direct drive generator. I. INTRODUCTION Direct drive permanent magnet generators (DD- PMGs) are becoming increasingly important for large- scale wind turbines as they remove the need for a gearbox and the high maintenance costs associated with using them. In direct-drive configuration the wind blades are directly connected to the generator, which therefore runs at a low speed (e. g. about 20 rpm). However, the low speed DD-PMGs for high power applications requires bigger machines able to produce high torque. In order to reduce the generator weight and size, all existing large- scale DD-PMGs use expensive rare earth magnets with high energy density [1-5]. The required amount of permanent magnets in various PMSG configurations depends on the generator size, operation speed and thermal aspects. Usually, large direct drive PM wind generators requires huge amount of magnet material. In literature values of 0.6t to 1t per 1MW are given [1, 6]. Considering that, the rare-earth magnet materials have a much higher specific cost than laminated steel and copper, in many cases, the cost of PMs is a significant part of the total machine costs [4, 5]. Moreover, the increase in the price of rare earths adversely affected wind turbine manufacturers’ production costs and profit margin. Therefore, reduction of expensive magnet materials by wind generators is of main interests for reducing their costs. To this topic, different substation strategies for reducing the use of rare-earths in wind turbines, such as, increasing the material efficiency, substitution of rare earth in permanent magnets, or use alternative technologies to PMSGs, have been addressed in [7, 8]. Further, in [9] a ferrite magnet alternative design (to the NdFeB) has been shown to be a competitive solution on costs of energy basis. Another method to reduce the magnet amount by PM machines without weakening their performances is proposed recently in [10]. Here different from the recent techniques, the reduction in the magnet amount has been achieved by improving the utilization of permanent magnets on the air-gap flux density production. In this paper, the new PM rotor with highly utilized magnets was investigated for DD-PMGs application. Section 2 describes briefly the new PM rotor configuration. The analytical approach for air-gap flux density is given in section 3. Afterwards, the machine parameters are derived in section 4. The first rough generator design using the analytical approach is derived in section 5. Finally, section 6 investigates the new PM rotor for wind power generator applications with the focus reduction of magnet amount for the same power compared with the common surface magnets rotors. As exemplary generator, a 10MW DD offshore PMSG is considered according to the specification given in [11]. II. NEW PM ROTOR DESIGN A new PM rotor configuration that operate with the 3 rd rotor magneto motive force (MMF) harmonic as operating wave was proposed in [10] and is illustrated in the following Fig. 1. The realization of this rotor type was achieved as a combination of two different rotor topologies, e.g. the first rotor with lateral magnets and additional flux-barriers (FB), and a second configuration with spoke magnets and with lateral magnet-slots as flux- barrier (FB). Moreover, the permanent magnets of the first and the second configuration are magnetized oppositely. In addition to that, the both rotor configuration produce a sub-harmonic component on the rotor MMF, however using flux-barriers, these component will be reduced and transformed to the operating 3 rd harmonic. Furthermore, by combination of rotor 1 and 2 in one rotor core the 1 st MMF harmonic will be able to reduced or completely cancelled, while the 3 rd or the working harmonic will be increased. This result on the reduction of rare earth magnet amount required for torque/power generation. III. AIR-GAP FLUX DENSITY ANALYSIS Reference [12] presents an analytical approach to determine the no-load air-gap flux density for the PM machines with the new rotor configuration. According to Ampere’s circuital law, and neglecting the MMF’s drop in stator and rotor iron portions, the radial air-gap field PM Wind Generator with Reduced Amount of Rare-Earth Magnet Material G. Dajaku*, and D. Gerling** *FEAAM GmbH, 85579-Neubiberg, Germany **Bundeswehr University Munich, 85579-Neubiberg, Germany  978-1-7281-1356-2/19/$31.00 ©2019 IEEE