4. Application conditions and requi

4. Application conditions and requirements4.1 GeneralThe bearings must be special for wind power. The detailed gearbox designation information including rated power, rated speed, transmission ratio, gearbox structure, gear parameters, drive train dimensions and tilted angle, torque arm stiffness, lubrication and cleanness, calculating temperature, temperature difference between inner and outer ring, gearbox parts material parameters, etc, will be delivered in specific project documents. Bearing suppliers shall strictly follow these documents’ requirements in bearing calculation4.2 Gearbox loadThe detailed load file including equivalent, maximum and extreme load will be attached in other load documents named in specific code like DVP-xxxxxxx. All calculations shall be based on the specific load documents.4.3 Design life time and contact stress4.3.1. Dynamic calculationThe dynamic raceway calculations shall be calculated according to ISO 281 and ISO/TS 16281. All values of the basic dynamic radial load rating Cr that deviate from the ISO 281 calculation must be justified. Basic (reference) rating life L10h and modified (reference) rating life L10mrh are considered to evaluate the bearing performance. The criteria are list in Table 3.1. Envision must be informed once the modified rating life was considered with EPAdditive.4.3.2. Design life time and contact stress at dynamic conditionUnder equivalent, rated and extreme torque, the contact stress between rollers and bearing raceways must meet the requirement of IEC61400-4 when misalignment has been accounted for (The criteria are list in Table 3.1). The Fa/Fr ratio must not exceed that recommended by the bearing manufacturer. When cylindrical roller bearings are used to support radial loads combined with axial loads, the fatigue bending strength must be demonstrated. Planet carrier bearing should also take both axial and accelerated load into consideration, meanwhile, if it is cylindrical roller bearing, bearing flange strength should be evaluated and approved by Envision.