Pseudo-rotor flux oriented control for deep bar effect compensation

Abstract

In an induction machine with deep rotor bars, the rotor parameters change due to skin effect and saturation, and the skin effect is often modeled as a ladder network. For the high performance drive of an induction machine with deep bar, many sophisticated control strategies and machine models have been discussed. As a control strategy, a complicated airgap flux oriented control scheme is mostly adopted because it is not possible to define a unique rotor flux in deep bar model. However, a unique pseudo-rotor flux can be defined and it is straightforward to achieve independent control of pseudo-rotor flux and torque. This control scheme can be applied to any n-th multiple ladder network. In this paper, it is shown that a deep bar effect is negligible when performing the proper field oriented control for an induction machine. Introducing an indirect pseudo-rotor flux oriented control scheme, the conventional rotor flux oriented control using equivalent rotor parameters are effective for deep bar and/or double cage machine. The actual IGBT inverter systems with a high precision torque transducer are implemented and thoroughly tested on a 250 HP induction machine for vector control operation and a 5.5 kW double cage induction machine to confirm its validity.