Tausif Husain

A Pulse-Injection-Based Sensorless Position Estimation Method for a Switched Reluctance Machine Over a Wide Speed Range

In this paper, a pulse-injection-based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. In this method, a single high-frequency pulse is injected in an idle phase to determine the rotor position at high speeds. The proposed method estimates the rotor position through analysis of the resultant current after voltage pulse injection. A low-speed sensorless method previously developed based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed pulse injection with varying duty ratios provided uniform sensing thresholds over varying dc bus voltages. The low- and high-speed methods are integrated together to provide a robust wide-speed-range rotor position estimator for SRM.

Design Methodology of a Switched Reluctance Machine for Off-Road Vehicle Applications

This paper presents the design of a switched reluctance machine (SRM) for off-road hybrid electric vehicle applications. SRMs are ideally suited for this application for their low cost, fault tolerance, and reliable operations. A multistage fast design methodology for SRM is presented in this paper. The process aims to determine the best speed at which the SRM would start single-pulse mode operation. This ensures the best efficiencies over the specified operating range. The machine is initially designed at that operating point using analytical design tools and then further optimized through finite-element analysis (FEA). The designed machine has been prototyped and then experimentally tested.

Analytical modeling of a novel transverse flux machine for direct drive wind turbine applications

This paper presents a nonlinear analytical model of a novel double sided flux concentrating Transverse Flux Machine (TFM) based on the Magnetic Equivalent Circuit (MEC) model. The analytical model uses a series-parallel combination of flux tubes to predict the flux paths through different parts of the machine including air gaps, permanent magnets (PM), stator, and rotor. The two-dimensional MEC model approximates the complex three-dimensional flux paths of the TFM and includes the effects of magnetic saturation. The model is capable of adapting to any geometry which makes it a good alternative for evaluating prospective designs of TFM as compared to finite element solvers which are numerically intensive and require more computation time. A single phase, 1 kW, 400 rpm machine is analytically modeled and its resulting flux distribution, no-load EMF and torque, verified with Finite Element Analysis (FEA). The results are found to be in agreement with less than 5% error, while reducing the computation time by 25 times.

Design of a modular E-Core flux concentrating axial flux machine

In this paper a novel E-Core axial flux machine is proposed. The machine has a double stator-single rotor configuration with flux concentrating ferrite magnets, and pole windings across each leg of an E-Core stator. E-Core stators with the proposed flux-concentrating rotor arrangement result in better magnet utilization and higher torque density. The machine also has a modular structure facilitating simpler construction. This paper presents a single phase and a three-phase version of the E-Core machine. Case study for a 1.1 kW, 400 rpm machine for both the single phase and three-phase axial flux machine is presented. The results are verified through 3D finite element analysis.

A pulse injection based sensorless position estimation method for a switched reluctance machine over a wide speed range

In this paper, a pulse injection based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. A single high-frequency pulse is injected in an idle phase and the rotor position is estimated through analysis of the resultant current after the voltage pulse injection. Low speed sensorless method developed previously based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed variable pulse injection duty ratio provided uniform sensing thresholds over varying DC bus voltages. The low speed and high speed methods can be integrated together to provide a robust wide speed range rotor position estimator for SRM.

Flux-Weakening Control of Switched Reluctance Machines in Rotating Reference Frame

A flux-weakening control for switched reluctance motors (SRMs) in the rotating reference frame is proposed in this paper. This rotating reference frame control of SRM mimics the control of synchronous machines (SMs). The method uses the periodic nature of the quasi-sinusoidal static torque characteristics to establish the rotating reference frame. A novel negativity removal block and a simplified nonlinearity handling block are introduced to ensure a smooth torque sharing among different phases and adjust for the SRMs unique operating principle. In the dq control method, a d-axis current is commanded for weakening the flux. An adaptive control method that uses the commanded and actual currents determines the required amount of flux weakening. Through the unique features of dq controls, the proposed method offers smooth torque at low speed and supports a wide-speed operation. The proposed control method is verified experimentally.

Design considerations of a transverse flux machine for direct-drive wind turbine applications

This paper presents the design considerations of a double-sided transverse flux machine (TFM) for direct-drive wind turbine applications. The TFM has a modular structure with quasi-U stator cores and ring windings. The rotor is constructed with ferrite magnets in a flux-concentrating arrangement to achieve high air gap flux density. The design considerations for this TFM with respect to initial sizing, pole number selection, key design ratios, and pole shaping are presented in this paper. Pole number selection is critical in the design process of a TFM because it affects both the torque density and power factor under fixed magnetic and changing electrical loading. Several key design ratios are introduced to facilitate the design procedure. The effect of pole shaping on back-emf and inductance is also analyzed. These investigations provide guidance toward the required design of a TFM for direct-drive applications. The analyses are carried out using analytical and three-dimensional finite element analysis. A prototype is under construction for experimental verification.

DC assisted bipolar switched reluctance machine

In this paper, a sinusoidally excited four-phase switched reluctance machine (SRM) with modified DC assisted windings is presented. The proposed four-phase SRM configuration with modified DC windings has reduced number of controllable phases and power converter devices. The DC winding configuration is modified from its traditional form by taking advantage of the machines inherent 90 degree phase shift between adjacent phases to achieve the desired simplification in the drive. Different power electronic converters that can be used with the proposed winding configuration have also been investigated. The proposed concepts are then verified through coupled FEA circuit simulations on a case study motor.

Dq control of switched reluctance machines

A method to control switch reluctance motors (SRM) in the dq rotating frame is proposed in this paper. The torque per phase is represented in this paper as the product of sinusoidal inductance related term and sinusoidal current term in the SRM controller. The SRM controller works with variables similar to that of synchronous machine (SM) controller in dq reference frame which allow the torque to be shared smoothly among different phases. The proposed controller provides efficient operation over the entire speed range and eliminates the need for an angle decoder. The controller achieves low torque ripple at low speeds and can apply phase advancing using a mechanism similar to the flux weakening of SM to operate at high speeds. The effectiveness of the proposed controller is verified through coupled finite element and circuit simulations.

Design of a switched reluctance machine for off-road vehicle applications based on torque-speed curve optimization

Design of a Switched Reluctance Machine (SRM) for off-road hybrid electric vehicle applications is presented in this paper. SRMs are ideally suited for this application for their low cost, fault tolerance and reliable operations. A methodology to get an optimized design for meeting the torque-speed requirements is developed. The process aims in determining the best speed at which the SRM would start single pulse mode operation for a given set of specifications while delivering the best efficiencies over the specified operating range. The designed machine has been prototyped and then experimentally tested.