Based on the power flow model of high speed motorized spindle

by using tribology and electromagnetics theory

the heat rate of bearing and the electromagnetic loss of built-in motor are respectively calculated.Utilizing the heat transfer theory

the thermal boundary conditions of spindle are calculated.On this basis

the finite element analysis model of the motorized spindle is built and calculated.The results show that front bearing

front end of spindle and stator are the most serious parts of temperature rise for motorized spindle;and in the initial stage of spindle operation

temperature rise of spindle is the fastest.Therefore in order to improve the spindle thermal characteristics

not only cooling device should be added in the serious parts of temperature rise

but also in the start-up phase

the motorized spindle should be cooled and lubricated effectively.