Search

Abstract Potential uses for electromagnetic launchers in defense systems, space exploration, and transportation have recently emerged. In addition, this accelerator has many applications, such as deploying small satellites into low-earth orbit and accelerating high-speed trains (e.g., bullet trains and Hyperloop) with a low-cost propulsion system instead of expensive linear motors, particularly in space applications. Therefore, the full capability and optimization of these launchers’ efficiency are still required. Therefore, this paper focuses on presenting a new design to decrease the coil’s magnetic circuit reluctance and boost the magnetic flux lines by adding a laminated iron yoke surrounding the coil. This design makes the inductance value of the iron-yoked accelerator twice the inductance in case of the absence of the iron-yoke at its peak. Additionally, the initial inductance of the iron-yoked accelerator is approximately 65% higher than that of the coil without the iron yoke. Consequently, the modified design proposed an efficiency of 17.5%, which represents a 60% improvement over the efficiency of the regular accelerator. In addition, the introduced design eliminates the suck-back force using a fast-switching device (IGBT) to switch the coil off when the projectile reaches half of the coil. Moreover, a mathematical model for the iron-yoked accelerator is built on MATLAB Simulink and validated experimentally. An artificial intelligence optimization technique, the gravitational search algorithm (GSA), is used to optimize the accelerator parameters, such as the number of turns, capacitor value, and capacitor voltage. Finally, the experimental evaluation of the GSA-optimized system demonstrated an additional 15% enhancement in efficiency, bringing the total efficiency to 20%.

Summary LLC resonant converter has been widely employed in electric vehicle (EV) charging applications. Compared with single‐phase LLC converters, three‐phase LLC converters provide a smaller current ripple, higher power capacity, and higher power density at higher power levels. However, the conventional three‐phase LLC converter, which adopts pulse frequency modulation (PFM), has the issue of limited gain range. In this paper, a three‐phase LLC resonant converter with variable magnetizing inductance is proposed. A two‐stage control strategy of PFM and fixed‐frequency magnetizing inductance modulation (MIM) is proposed. The wide gain range needed for EV charging is realized by modulating magnetizing inductance and frequency. Finally, a 2.7 kW prototype with 400 V input and 280–420 V output range verifies the theoretical analysis and parameter design. The experimental results show that the converter can achieve soft switching and a wide gain range and the peak efficiency is 97.7%. [ABSTRACT FROM AUTHOR]

Rotary electromagnetic fault current limiter (FCL) is an emerging technology for limiting fault currents in the power network. The device consists of two movable air-core spherical reactor rings (i.e., inner and outer rings). The movable feature allows the reactor rings to rotate, and form a proper mutual positional displacement. This can limit the fault current since the effective inductance of the device is dependent to the mutual angular position of the reactor rings. Due to the unconventional structure, to this date, the design process has solely been based on finite element (FE) method. This paper aims to analytically validate the theory and the overall functionality of the device in both the steady state and transient regime. For this propose, the resistance and the inductance of the device are first computed at normal operating condition using the basic theory of engineering electromagnetics. Next, performance characteristics such as electromagnetic torque, rotational displacement of the reactors, effective inductance of the device, and the network current are calculated at the faulty condition. For verification purposes, analytical results are compared with via FE simulation and experimental test.

Recent developments in electromagnetic launchers have created potential applications in transportation, space, and defense systems. However, the total efficiency of these launchers has yet to be fully realized and optimized. Therefore, this paper introduces a new design idea based on increasing the magnetic flux lines that facilitate high output velocity without adding any excess energy. This design facilitates obtaining a mathematical equation for the launcher inductance which is difficult to analytically represent. This modification raises the launcher efficiency to 36% higher than that of the ordinary launcher at low operating voltage. The proposed design has proven its superiority to traditional launchers, which are limited in their ability to accelerate microsatellites from the ground to low Earth orbit due to altitude and velocity constraints. Therefore, an aircraft is used as a flying launchpad to carry the launcher and bring it to the required height to launch. Meanwhile, it is demonstrated experimentally that magnetic dipoles in the projectile material allow the launcher coil’s magnetic field to accelerate the projectile. This system consists of the launcher coil that must be triggered with a high amplitude current from the high DC voltage capacitor bank. In addition, a microcontroller unit controls all processes, including the capacitor bank charging, triggering, and velocity measurement.

A wide-band LC-tank CMOS voltage controlled oscillator (VCO) employing a transformer-based variable inductance structure is presented. The variable inductance is obtained through a switching scheme that controls the current path in a transformer and allows four different inductances to be delivered by the structure. Additionally, an electric model of the transformer obtained through the simulated data and equations based on its physical properties is proposed. The inductance and quality factor from the variable structure were extracted from the transformer's electromagnetic simulations and model's scattering parameters. The model showed and error lower than 4% in all modes of operation inside of the desired range (from 1 to 6 GHz). The proposed VCO is simulated and shows a percentual tuning range of 87.9% around a central frequency of 4.12 GHz, while consuming less than 3.3 mW of power and exhibiting a maximum phase noise of -108 dBc/GHz occupying an area of 0.45 mm 2. • An 87.6% tuning range wide-band VCO with variable inductance is simulated. • The variable inductance utilizes 3 switches to deliver 4 different inductance values. • A body floating technique is used to mitigate the switches' impact on the inductance. [ABSTRACT FROM AUTHOR]