A study for starting characteristic analysis method of salient pole synchronous motors

Solid rotors can be adapted to synchronous motors of 5 MW and over in applications with high inertia loads. The eddy currents induced in the solid pole are used for starting of the motor and their paths are changed depending on the design of the rotor shape unlike the synchronous motors with damper windings or cages. In this paper, the starting characteristic of a 7 MW solid salient pole synchronous motor is analyzed by the combined methods for two and three-dimensional finite element models because a three-dimensional analysis to solve the problem is difficult due to the long solving time. The maximum difference between results of the combined method for two and three-dimensional finite element analysis and the factory test is less than 10%.

I. Introduction

Synchronous motors can be classified into the solid (or massive) and laminated rotor types according to core construction. The main advantage of the lamination type is low eddy current losses due to the insulated electrical sheets. The rated output of this type may be restricted to about 14 MW due to the relatively low mechanical stability of the rotor because of the critical speed limit and the overheating of damper windings. When large inertia of the load or high structural stability of the rotor is required, the solid rotor started by eddy currents inside a rotor core can be applied for synchronous motors of 5 MW and over.