Radial force cancellation of bearingless brushless direct current motor using integrated winding configuration

A bearingless brushless direct current (BLDC) motor incorporates the function of magnetic bearings into a BLDC motor, making it a new type of high-performance motor. In this paper, the main motor windings are used to generate the radial force cancellation by injecting the required dc current, “integrated winding configuration”. The bearingless BLDC motor, direct current (DC) cancellation system model is established with the aid of (ANSYS/MAXWELL) software. The simulation results confirm that the rotor radial force is approximately zero and results from a balanced distribution of the magnetic flux density. The proposed DC excitation system is suitable to realize the rotor radial force cancellation in the bearingless BLDC motor. The simulation results of the proposed configuration show the approach of integrating winding configuration at different active pole positions to find the more efficient suspension performance and reduce the suspensions system current.

Design and Thermal Modeling of Modular Hybrid Excited Double-Sided Linear Flux Switching Machine

This paper presents a Hybrid Excited Double-Sided Linear Flux Switching Machine (HEDSLFSM) with a crooked tooth modular stator. Generally, the conventional stators are made of a full-length iron core, increasing manufacturing costs and iron losses. Higher iron losses result in lower efficiency and lower overall performance. A U-shaped modular stator with a crooked tooth is used to lower iron consumption and increase the machine’s efficiency. Ferrite magnets are used to replace rare earth magnets, which also reduces the machine cost. Two DC excitation windings are used above and below the ferrite magnet to reduce the PM volume. 2D electromagnetic performance analysis is done to observe the key performance indices. Geometric optimization is used to optimize the Split Ratio (S.R), DC winding slot area (DCw), and AC winding slot area (ACw). Stator Tooth Width (STW), space between the modules (S.S.), and crooked angle (α) are optimized through JMAG in-built Genetic Algorithm (G.A.) optimization. High thrust force density and modular stator make it a good candidate for long-stroke applications like railway transits. The thermal analysis of the machine is performed by FEA analysis and then validated by 2D LPMC (Lumped Parametric Magnetic Equivalent Circuit) model. Both analyses are compared, and an error percentage of less than 4% is achieved.

Research on Frequency Doubling Effect of Thermoacoustic Speaker Based on Graphene Film

In this work, the frequency doubling effect of thermoacoustic speakers is studied, and a method is analyzed to suppress the frequency doubling effect. Three cases were analyzed by superimposing the DC bias on the AC excitation: (1) DC is less than AC; (2) DC is equal to AC; (3) DC is greater than AC. We found that the frequency doubling effect can be well suppressed by superimposing a larger DC excitation on the AC excitation. The laser scribing technology was used to prepare graphene film in only one step, and the screen printing technology was used to prepare conductive electrodes. The microphone and B&K system was used to record the sound pressure level and study the suppression of frequency doubling effect. Finally, the sound pressure levels with the three different kinds of excitations were measured. The measured results show that they have a good agreement with the theoretical results. The suppression effect will be better when DC amplitude is greater than AC amplitude. Therefore, this work has certain reference significance for the further study and application of thermoacoustic speakers.

HV Transformer Protection and Stabilization under Geomagnetically Induced Currents

This paper presents the results of research related to the issues arising from DC excitation of power transformers due to geomagnetically induced currents (GIC). First, the GIC phenomena and their influence on power system operation are discussed. Then, a recorded case of tripping of the transformer differential protection due to geomagnetic disturbances (GD), as well as simulation signals from a developed model of a transformer subjected to a GD are analyzed. Next, two algorithms for GIC detection utilizing the rate of change of transformer differential currents and the DC component in the neutral current are proposed, thoroughly tested, and recommended.

Electrical machines with switched and modulated flux

The work compares the value of the produced torque (average value) of a 2.2kW squirrel cage induction motor with new construction machines, i.e. a motor with flux switching and hybrid excitation or DC excited, a motor with flux modulation and hybrid excitation or DC excitation. The external dimensions of the tested machines corresponded to the dimensions of the induction motor.

AC and DC Differential Bridge Structure Suitable for Electrochemical Interfacial Capacitance Biosensing Applications

This paper presents a capacitive differential bridge structure with both AC and DC excitation and balancing capability for low cost electrode-solution interfacial capacitance biosensing applications. The proposed series RC balancing structure offers higher sensitivity, lower susceptibility to common-mode interferences, and drift control. To evaluate the bridge performance in practice, possible effects of initial bridge imbalance due to component mismatches are investigated considering the required resolution of the balancing networks, sensitivity, and linearity. This evaluation is also a guideline to designing the balancing networks, balancing algorithm and the proceeding readout interface circuitry. The proposed series RC bridge structure is implemented along with a custom single frequency real-time amplification/filtering readout board with real-time data acquisition and sine fitting. The main specifications for the implemented structure are 8-bit detection resolution if the total expected fractional capacitance change at the interface is roughly 1%. The characterization and measurement results show the effectiveness of the proposed structure in achieving the design target. The implemented structure successfully achieves distinct detection levels for tiny total capacitance change at the electrode-solution interface, utilizing Microcystin-(Leucine-Arginine) toxin dilutions as a proof of concept.