A Light-Weight Rotor Design for Brushless Doubly Fed Machines

Abstract

In this paper, a new optimized rotor design for Brushless Doubly Fed Machines (BDFMs) is proposed. The BDFM is considered as an attractive generator particularly for offshore wind power generation and also as a replacement for doubly fed slip ring induction generators. This is due to its higher reliability and lower maintenance reported in the literature. It is shown in this paper from the study of the magnetic field distribution in the rotor core that the conventional design of the BDFM rotor iron core can be modified, leading to a lighter machine. The proposed design method is supported by an analytical study and its practicality is validated using 2-D Finite Element (FE) analysis. A 250 kW experimental BDFM with frame size D400 is considered as the prototype machine. Index Terms-Brushless doubly fed machine (BDFM), rotor back iron, finite element analysis (FEA), magnetic circuit, iron saturation, magnetic flux density.

Rotational Iron Losses in Brushless Doubly Fed Machines

“…In this configuration, the total iron loss can be obtained by subtracting the stator cupper losses from the measured input power when the machine operates at no-load and locked-rotor condition. (11) Pin is the total input power to stator PW and CW and the Pcu-PW and Pcu-CW are the copper losses dissipated in the stator PW and CW, respectively. Once the FE model is solved, the local flux density waveforms for both the stator and rotor regions are extracted from the FE solution.…”

“…Due to the presence of two magnetic fields with different pole numbers and frequencies generated from the stator windings, the field pattern in the BDFIM's magnetic circuit is more complex than the conventional induction machines [11]. This makes the analysis and modelling of the BDFIM challenging.…”

Internal mode control based coordinated controller for brushless doubly fed induction generator in wind turbines during fault conditions

“…The stator winding which is directly connected to the grid is called the power-winding (PW) while the other which is connected to the grid through a power electronic (PE) converter is called the control winding (CW) [15]. The most commonly used construction for BDFIGs is the nested-loop rotor construction [16]. In this construction, aluminum or copper bars are used to create many nests with multiple loops.…”