Arun Gandhi

Recent Advances in Modeling and Online Detection of Stator Interturn Faults in Electrical Motors

Online fault diagnosis plays a crucial role in providing the required fault tolerance to drive systems used in safety-critical applications. Short-circuit faults are among the common faults occurring in electrical machines. This paper presents a review of existing techniques available for online stator interturn fault detection and diagnosis (FDD) in electrical machines. Special attention is given to short-circuit-fault diagnosis in permanent-magnet machines, which are fast replacing traditional machines in a wide variety of applications. Recent techniques that use signals analysis, models, or knowledge-based systems for FDD are reviewed in this paper. Motor current is the most commonly analyzed signal for fault diagnosis. Hence, motor current signature analysis is a topic of elaborate discussion in this paper. Additionally, parametric and finite-element models that were designed to simulate interturn-fault conditions are reviewed.

Thrust Optimization of a Flux-Switching Linear Synchronous Machine With Yokeless Translator

Linear permanent magnet machines have been increasingly used in several applications that require high reliability and good dynamic characteristics. In this paper, a novel double-sided design of a 3φ permanent magnet flux-switching linear synchronous machine (FSLSM) with a yokeless translator is proposed. It is found that the proposed design can achieve more than 50% higher thrust than a conventional FSLSM and excellent linearity even under high excitation currents. Optimization of the proposed machine is performed using individual parameter optimization and is compared with results from global optimization using genetic algorithm (GA). Force analysis of the proposed design is performed to establish the mechanical integrity of the design. The proposed FSLSM is most suitable for long-stroke applications and intermittent oscillatory type applications.

Design and control of fault-tolerant permanent magnet machines

This paper discusses design and control techniques for fault tolerant permanent-magnet (PM) machines that are suitable for applications where safety is of paramount importance. Back-EMF based design and analysis approach for a multiphase air-core linear motor has been presented in this paper. Apart from the design approach, fault tolerant techniques for current control in both time and frequency domains have also been discussed. In time domain, an iterative learning based control method is also presented and is found to be very robust. Both open-circuit and short-circuit fault tolerant operation have been discussed in this paper.

Thrust optimization of a five-phase fault-tolerant flux-switching linear synchronous motor

Linear permanent magnet machines have been increasingly used in several applications that require high reliability and good dynamic characteristics. In this paper, a novel double-sided design of a 5φ permanent magnet flux-switching linear synchronous machine (FSLSM) with a yokeless translator is proposed. The proposed design is analyzed using finite-element methods and is found to have high thrust and low cogging force. It is shown that thrust ripples of less than 1% is achievable by redesigning the currents. The proposed 5φ machine is optimized using individual parameter optimization and is compared with results from global optimization using genetic algorithm (GA). The machine is analyzed for different open-circuit fault conditions and it is found that by including the reluctance component of the thrust, thrust ripples under fault can be minimized. The proposed FSLSM is most suitable for long-stroke applications and intermittent oscillatory type applications especially when safety is a critical factor.

Doubled-sided FRLSM for long-stroke safety-critical applications

Permanent-magnet linear synchronous motors (PMLSMs) are increasingly preferred in the industry wherever linear motion is required because of their high reliability and excellent dynamic characteristics. In this paper, a modified double-sided design of a linear motor for long-stroke applications is introduced. The proposed motor utilizes a flux-reversal topology and hence requires lesser number of permanent magnets (PMs) for operation than PMLSMs with magnet tracks. Comparison is made with conventional single-sided flux-reversal motor configuration, which shows 33% increase in thrust producing capability in the proposed design without an increase in excitation sources. Additionally, mover weight is reduced significantly, which can improve the dynamic characteristics of the motor. A five-phase 5-slot/11-pole flux reversal motor based on the double-sided topology is introduced for use in safety-critical applications. The proposed five-phase motor has low detent force and improved thrust density.

Double-sided flux-switching linear synchronous machine with yokeless translator

In this paper, a novel double-sided design of a 3υ permanent magnet flux-switching linear synchronous machine (FSLSM) with a yokeless translator is proposed. When compared to conventional flux-switching linear machines, it is found that the proposed design can achieve 56% higher thrust without compromising other features of the conventional flux-switching motor. The proposed design also exhibits excellent thrust versus current linearity even under high excitation currents. Force analysis of the proposed design is performed to establish the mechanical integrity of the design. The proposed linear motor is suitable and cost-effective for applications that require long strokes and may also, find uses in repeated oscillatory type applications.

Double-Rotor Flux-Switching Permanent Magnet Machine With Yokeless Stator

In this paper, novel design of a flux-switching permanent magnet machine (FSPMM) with a yokeless stator and two rotors has been proposed. The proposed machine has been found to perform on par with a 6-slot/13-pole C-core conventional FSPMM in terms of torque output. Additionally, the proposed machine has no significant unbalanced magnetic forces, which is a major challenge in conventional FSPMM with odd number of rotor poles. Step-by-step parametric optimization has been performed using finite-element models of the machine in order to achieve the highest torque with the given magnetic and electrical constraints.

Hybrid flux-switching linear machine with fault-tolerant capability

Safety critical applications such as in naval and aerospace industries demand electrical drives with fault-tolerant capabilities. A novel hybrid flux-switching linear machine capable of operating reliably under short-circuit faults is proposed in this paper. The proposed topology has a yokeless translator and two stator modules. Alnico magnets along with DC windings are used to provide the field excitation. It has been shown that by controlling the current through the DC field windings, magnet flux can also be controlled. Under a short-circuit fault in one of the windings, it is seen that by turning the magnet off, the fault current is reduced to 50% of its original value. Also, the phase windings of the proposed machine have high self inductance and low mutual inductances thereby, achieving good phase isolation for fault-tolerance.