The primary goal of this study is to create a magnetic levitation system for additive manufacturing (AM) applications. The emphasis of this research is placed on Laser Directed Energy Deposition via Powder Feeding (LDED-PF). The primary benefit of using a magnetic levitation system for AM applications is that the levitated geometry is expected to be a portion of the final part manufactured, thus eliminating the need for a substrate and reducing the post-processing operation requirement. Two novel levitation systems were designed, optimized, and manufactured. The design, optimization, and analysis were first conducted in the simulation environment using ANSYS Maxwell and then tested with experiments. The newly developed systems depicted a much-improved performance compared to the first prototype developed in a previous article written by the authors. The newly developed systems had an increase in levitation height, the surface area for powder deposition activities, the time available for AM operations, and the ability to support additional mass within the limits of allowable inputs. The compatibility of the levitation system with AM applications was also verified by testing the impact of powder deposition and the ability of the levitated disc to support added mass as a function of time with minimal loss in performance. This article also highlights the development of a novel feedback PID controller for the levitation system. To improve the overall performance of the controller, a feedforward controller was added in conjunction with the PID controller. Finally, the levitation system was shown to highlight control over levitation height and maintain constant levitation height with the addition of an added mass using the feedback controller. 

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Development and Analysis of a Novel Magnetic Levitation System with a Feedback Controller for Additive Manufacturing Applications

Impedance behavior of laminated core inductor is studied at different frequency. Winding parasitic parameters which increase with the operating frequency due to skin effect and proximity effect are considered. These parameters can be modelled with dc resistance, winding dielectric capacitance, and magnetic core loss. These parameters may be calculated from standard data sheet parameters of the copper conductor and laminated sheets. The windings of electrical machines such as transformers, rotating machines, have been studied by various researchers to determine its state of health during operation. Different methods have been employed such as Sweep Frequency Response Analysis (SFRA), Motor Current Signature Analysis (MCSA) etc., to determine its condition at different frequencies. SFRA can offer detailed insight into condition of the winding insulation by analyzing the impedance of the winding over its bandwidth, however it is limited to offline implementation due to the invasiveness of the technique. The purpose of this paper is to lay the foundation for further development of the technique towards online implementation using an inverter, by firstly considering the case of an inductor. This will allow for a better understanding of the bandwidth and impedance model (including parasitic parameters, associated with the device) before translating the model and implementation to a rotating electric machine. Therefore, this paper sets out to explore the impedance for a standard round conductor winding silicon steel, by also considering parasitic components.

Impedance Behavioural Study of Silicon Steel Laminated Core Inductor

The induction machine (IM) is commonly adopted in industry, which plays an important role in energy conversion between mechanical and electrical power. Asymmetrical faults caused by internal failures commonly occur in IMs. Such faults not only reduce the working efficiency and cause excessive heating, but also cause potential hazards preventing continuous operation and safety problems. This paper proposes a power electronic converter-based IM power hardware-in-the-loop (PHIL) emulator, which is able to emulate an IM with internal faults. Firstly, the machine parameter measurement method for an induction motor with a rotor cage fault is introduced. Then the rotor cage fault machine is identified by using stator current spectral components. Based on that, the PHIL emulator is developed and tested for an IM with rotor cage fault. A comparison of the emulator results with simulation results and actual IM results demonstrates the validity of proposed solution.

Power-Hardware-in-the-Loop Based Induction Motor Emulator with Rotor Cage Fault

This paper presents an offline fault detection technique; sweep frequency response analysis (SFRA) which is carried out by implementing the impedance response method to detect an inter-turn winding fault in a silicon steel laminated core inductor (LACOIN). The proposed technique is based on the fundamental components of the winding's physical geometry which consists of the winding resistance (R), inductance (L), and capacitance (C). A comparative study of the equivalent winding resistance, reactance, and impedance under the healthy and winding inter-turn fault conditions is carried out using Dowell's equation. The equation considers both the skin and proximity effects which causes winding parasitic parameters (resistance and inductance) to increase with the operating frequency. The analytical winding parameters were validated experimentally for the healthy, 1%, 3%, and 6% inter-turn short-circuit fault conditions of the LACOIN's winding. The methodology requires a low frequency bandwidth (DC - 100 kHz) and a simple signal processing technique, i.e., Fast Fourier transform (FFT) to determine the impedance frequency response from the measured voltage and current signals. This also enable us to detect as low as 1% inter-turn short-circuit fault out of 350 turns in the windings of the LACOIN. The results show that, inter-turn faults mostly affect the inductive and capacitive region of the impedance response plot which reduces the impedance magnitude's peak and increases the resonant frequency, hence using impedance peak and resonance frequency as indicators.

Chigozie Boniface

Papers

Impedance Behavioural Study of Silicon Steel Laminated Core Inductor

Power-Hardware-in-the-Loop Based Induction Motor Emulator with Rotor Cage Fault

Winding Inter-Turn Fault Detection in a Silicon Steel Laminated Core Inductor using Sweep Frequency Response Analysis