Jesus Arellano-Padilla

Control of an AC Dynamometer for Dynamic Emulation of Mechanical Loads With Stiff and Flexible Shafts

This paper addresses the emulation of linear and nonlinear loads using a vector-controller dynamometer for the position control of mechanical loads. The emulation strategy allows an electrical machine (dynamometer) to be controlled, so as to emulate both the static and dynamic characteristics of a load with a certain bandwidth. The approach can be used for the experimental validation and testing of the electrical drives and motion-control techniques. The dynamic structure of the emulated load is always preserved. High-order systems such as loads with flexible shafts and nonlinear effects can be emulated accurately. This paper presents the dynamometer-control design, its practical implementation, and experimental results for the position control of the linear and nonlinear emulated loads. Systems with stiff and flexible shafts are considered. Finally, the experimental results are compared with the corresponding simulated loads to validate the emulation strategy

Inductance characteristics of PMSMs and their impact on saliency-based sensorless control

Advantages of operating a Permanent Magnet Synchronous Machine (PMSM) without a position sensor are many and are well known. This paper presents a study of the effects of space harmonics in the incremental inductances and their impact on the machine saliency. The effects of space harmonics exclusively due to the machine (i.e., the saturation saliency distribution) are given particular consideration. The results are illustrated through inductance analysis and measurement of inductance profiles of two similar PMSM machines. The space harmonics in the inductance profiles are correlated with the position estimate distortions through a Matlab/Simulink embedding finite element (FE) machine simulation. Significant differences in sensorless operation of the two machines are found which correlate to the inductance profiles. This illustrates that inductance profiling can inform upon machine design in order to improve sensorless capabilities.

Investigation of induction machine phase open circuit faults using a simplified equivalent circuit model

An induction motor model based on the per-phase equivalent circuit is used to simulate operation with an open circuit fault. The model considers both spatial field harmonics as well as saturation effects to correctly model the motors behaviour under faulty conditions, where the non-linearities may produce problematic torque pulsations due to the unbalanced nature of the winding distribution. A model is presented which takes into account the most prominent nonlinearities, however keeping simulation times low in order to enable the development of fault tolerant control strategies. In addition, this paper presents a study of the behaviour of an induction motor drive with a phase open circuit fault. A new fault remedial control strategy for this type of fault will also be described. Experimental tests on an instrumented vector controlled rig have been used to verify simulation results.

On-line detection of stator winding short-circuit faults in a PM machine using HF signal injection

This paper presents a high frequency (HF) injection scheme to detect short-circuits faults in the stator winding of a VSI-fed permanent magnet (PM) machine. The proposed approach is derived from sensorless control schemes based on HF voltage signal injection for tracking position in a surface-mount PM machine. In this paper the method of space-modulation profiling (SMP) is used to obtain a magnetic signature of the machine operating under healthy conditions. This signature can then be compared with the on-line measured saliency profile during normal operation to detect any abnormality in the drives performance. The main application of the presented scheme is for the detection of windings problems such as insulation breakdowns and short circuits. Experimental results are shown for the case of a PM servo drive where incipient and full short-circuit faults have been emulated and successfully detected. Due to its relatively simple implementation and since no additional transducers are required, this approach presents an interesting alternative for condition monitoring.

Diagnosis of incipient faults in PMSMs with coaxially insulated windings

Early detection of incipient faults in AC drives is one of the most difficult challenges for condition monitoring, especially for faults related to insulation degradation of the windings. This is because insulation degradation is very difficult to be detected on-line, so these faults may pass unnoticed before turning into a major faults. This paper looks at the feasibility of using coaxially insulated windings not only to increase reliability against winding insulation problems, but as an alternative to advance condition monitoring that may be suitable for the detection of insulation degradation, and other faults not easily detected by conventional schemes such as demagnetization issues, and the presence of inter-turn short circuits. The concept of insulation degradation for the case of coaxially insulated windings is analytically considered in this work and a novel condition monitoring alternative proposed. The proposed scheme and winding topology are extensively evaluated numerical to determine their feasibility to drive condition monitoring.

An investigation into the suitability of unbalanced motor operation, the Eh-star-circuit for stray load loss measurement

The concept of obtaining stray load loss results from a test on an unbalanced motor is examined and its advantages shown. Computed results are presented which confirm the potential of the method. Experimental results also support the idea that this type of test may have merit particularly for purposes of checking on quality of production where expensive test facilities are undesirable.

Operation of an induction motor with an open circuit fault by controlling the zero sequence voltage

This paper presents a fault ride through method for use when open circuit winding faults appear on an induction motor drive. A feed forward compensation term is introduced into the zero sequence component of the dq reference voltages which considerably reduces current and torque ripple in the faulted motor drive. If the machines “neutral point” voltage can be modulated, then a reasonably high speed can be achieved before field-weakening control is required. The paper describes the application of the control method to a delta-connected machine with an open winding fault, with an unmodified inverter drive. The proposed scheme has been verified by experimental results.

A simplified model for induction machines with faults to aid the development of fault tolerant drives

A new mathematical model of a three-phase induction machine, suitable for the simulation of machine behaviour under fault conditions is presented. The model employs a simple state space equivalent circuit based model of the induction machine, which is enhanced to include space harmonics and main flux saturation effects. The model has been improved by including a variation of machine inductances with rotor and flux position, and creates a simulation with reasonable accuracy and fast computation time. For healthy and fault conditions, comparisons show that the simulated saturation and space harmonic frequencies and magnitudes match those obtained from experiment. This model can be used to develop and optimise control strategies for fault ride through.

Permanent Magnet Synchronous machines for Saliency-based, Self-Sensored Motion Control

This paper first identifies and quantifies the saliency components in symmetric permanent magnet synchronous machines. The saliency component dependence on the geometry and operating regime of the machine will be investigated in an effort to set out guidelines for machine and control design of these type of machines.

Incipient Fault Diagnosis in Ultrareliable Electrical Machines

Early detection of incipient faults in ac drives is one of the most difficult challenges for condition monitoring, especially for faults related to insulation degradation of the windings. In low power motors, the insulation degradation is principally due to the steep voltage variations caused by the voltage source converters that drive the machines. In the last years, with the coming to market of new no-Si based power devices, which achieve great values of dv/dt, fast tracking of electrical fault has became a topic of primary importance. In this paper, a new method to detect the presence of incipient faults in ultrareliable electric machines is presented and compared with a previous solution. The different methods were extensively evaluated by means of experimental results. It is shown that potential winding faults can be detected at an early stage of fault inception and thus measures can be taken to limit propagation.