In all areas of engineering, testing full-scale models can be both costly and risky and often not necessary. The scaling laws can be implemented in electromagnetic launchers (EMLs). The objective is to obtain similar temperatures, magnetic induction, and stress fields (T, B, and S) compared to the full-size geometry. A few EML dimensions, such as its cross-section, rail separation, and length, must be scaled appropriately to obtain accurate results. Pulsed power supply (PPS) parameters require adjustments as well. However, designing a new PPS prototype requires considerable engineering time and budget. Therefore, in this study, scaling rules are studied utilizing an existing PPS. EMFY-4, a recently developed EML with a 50 x 60 mm concave bore and 6-m length, is scaled to be used with a 250 kJ capacitive PPS. A multi-objective optimization study is conducted to get the best design. The first objective is to get a minimum rail length to seek higher energy density. The second objective is to minimize the muzzle current to the peak rail current ratio for higher efficiency. The effect of armature mass, capacitor charging voltage, and the required number of PPS modules on the objective functions are discussed. The study showed that when the existing PPS is used, the scaling with the higher scaling factor, denoted as (λ), gives better results.

Refurbishment of hydro-generators promises an increased lifespan and improved efficiency. Old generators are not only less efficient but also less reliable; their fault occurrence is more common. The economic impact of out-service time can be astronomical. Thus, refurbishment is a critical task; but it is challenging too. Most of the conducted works focus on the material update, enhancing the cooling network, and obtaining better efficiencies. Modifying winding type, i.e. conversion from lap winding to wave winding is rare since it often requires a change in the slot number. Such a move can be laborious, size change can become mandatory. In this study, a refurbishment design strategy is proposed which includes a winding type conversion. The task is to implement a wave winding since it has less out-service time and is easily replaced by field workers. In this paper, an old generator that started operation in 1956 is used for a refurbishment. This study promises a guideline to hydro-generator designers who work on a refurbishment study on old hydro-generators that have diamond coils.

This paper presents a novel contactless field excitation~(CFE) system based on wireless power transfer~(WPT), which utilizes the existing voltage source inverter~(VSI) of the motor drive for electrically excited synchronous motors~(EESMs). In conventional CFE systems, an extra high-frequency converter is required to excite the field winding.  In this paper, it is proposed to utilize existing voltage switching harmonics of the VSI for exciting the field winding while the low-frequency modulated component is used to drive the motor. In the proposed system, a novel variable carrier phase shift method~(VCPSM) is developed to achieve constant input excitation voltage for the WPT part independently from the motor operation. In addition, a hybrid frequency detuning control method is introduced to adjust the field current.  For experimental validation, a small-scale prototype with 100~V DC-link and 60~kHz switching frequency is established. It is observed that the field current could be kept almost constant at 5~A under different motor driving conditions operations regarding modulation index and fundamental frequency.  Also, it is shown that the field current could be reduced by detuning the switching frequency. In brief, without an additional active converter and only with a software update, a cost-effective CFE system for EESMs can be easily implemented.

Early detection of an inter-turn short circuit fault (ISCF) can reduce repair costs and downtime of an electrical machine. In an induction machine (IM) driven by an inverter with a model predictive control (MPC) algorithm, the controller outputs are influenced by a fault due to the fault-controller interaction. Based on this observation, this study developed neural network models using inverter switching statistics to detect the ISCF of an IM. The method was non-invasive, and it did not require any additional sensors. In the fault detection task, an area under receiver operating characteristics curve value of 0.9950 (95% Confidence IntervaI: 0.9949 - 0.9951) was obtained. At the rated operating conditions, the neural network model detected and located an ISCF of 2-turns (out of 104 turns per phase) under 0.1 seconds, a speedup of more than two times compared to the thresholding-based method. Moreover, we published the switching vector data collected at various load torque and shaft speed values for healthy and faulty states of the IM, becoming the first publicly available ISCF detection dataset. Together with the dataset, we provided performance baselines for three main neural network architectures, namely, multi-layer perceptron, convolutional neural network, and recurrent neural network.

Muzzle voltage is an essential diagnostic tool used in both contact resistance modeling and transition determination. However, it is challenging to stem the necessary meanings from the collected measurements. In this study, EMFY-3 launch experiments are used to model muzzle voltage characteristics to understand the transition mechanism better. These experiments have muzzle energies in the range between 1.69-2.85 MJ in ASELSAN Electromagnetic Launcher Laboratory. Six different launch tests with various rail current waveforms that ranged between 1.5-2.1 MA are used to investigate different scenarios. Some parameters which affect muzzle voltage are calculated with the 3-D Finite Element Method (FEM), i.e., rail mutual inductance $\mathrm{L_m}$. Muzzle voltages are decomposed into subsections; each subsection is calculated with proper models. Simulation results are coherent with experimental measurements. Findings are compared with previous studies, and differences are explained with possible reasons. Even though we could not conclusively resolve which physical quantity starts to transition, the study showed that transition does not form a specific muzzle velocity, armature action integral, or down-slope rail current ratio.

ASELSAN Inc. has been working on electromagnetic launch technologies since 2014. The first prototype, EMFY-1, has a 25 mm × 25 mm square bore and 3-m-length rails. The second prototype, EMFY-2, has a 50 × 50 mm square bore and 3-m-length. In this paper, a recently developed prototype, EMFY-3, is presented, which has a 50 × 75 mm rectangular bore and 6-m-length. The input energy of the PPS is doubled to 8 MJ, and the 2.91 MJ muzzle energy is obtained up to now. Rail currents, breech, and muzzle voltages are measured to investigate electromagnetic calculations. Velocity curves are captured with Doppler radar, which enables us to establish propulsive inductance gradient L0pr transients empirically. The results confirm that L0 pr is constant throughout the launch, as no significant breaking mechanism occurs with the non-magnetic containment. However, a slight variation (%2 at maximum) happens from one launch to another with different rails’ current magnitudes. The transition phenomenon is a candidate for the drop in the L0 pr, as it occurs more likely at launches with higher linear current densities.

An important application for large-scale pulse power supplies (PPS) is electromagnetic launchers (EMLs). These de- vices utilized stored several MJs of electrochemical energy into linear mechanical energy. Because of extreme physical conditions, simulations are crucial in electromagnetic launcher (EML) research. As the operation risk rises, more en- ergy into the system adds weight to the model’s accuracy. In this paper, the electromagnetic impact of the bus structure is discovered in a recently developed EMFY-3 electromagnetic launcher, is presented. An H-shaped bus structure is used for the current injection. However, experiments showed that the H-shaped bus changes inductance calculations. A careful examination is made to reveal the physical reasoning behind the bus impact. We hypothesize that the rail portion surrounded with bus geometry has less inductance than the rest due to the eddy current created by rail current transients, which should be calculated carefully through numerical calculations, i.e., 3-D Finite Element Method (FEM). Two dif- ferent simulation models were constructed to test the hypothesis. Moreover, rail currents, breech, and muzzle voltages are measured to investigate electromagnetic calculations. Results showed a good agreement with experiments where the bus structure was modeled explicitly. That aspect showed that the bus structure should be well-examined when multiple PPS are connected.

In this paper, a novel and non-invasive stator inter-turn short circuit (ITSC) online detection method is presented for an induction machine (IM), driven by a two-level voltage source inverter (2L-VSI) via finite control set model predictive control (FCS-MPC). The main idea of the proposed method is to utilize the controller itself as an observer: under the presence of a fault, the distribution of inverter switching states significantly deviates from the original balanced case. Therefore, by inspecting the inverter switching vectors, which are the outcomes of the FCS-MPC routine’s online optimization procedure, a stator fault can be detected efficiently. It is observed that both the zero-vector allocation over the complex plane and the allocation among the active vectors are influenced by the presence of a stator short-circuit fault. The proposed fault detection strategy introduces little to no extra burden for processor and memory. Experimental results verify the proposed method, and inter-turn short circuits of two and three turns are confidently detected and located for a 500 W, two-pole IM.

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