In this paper, we discuss a position sensorless drive for an axial structure motor without rare-earth metals in a low-speed region. Since this motor has no saliency, a conventional position sensorless drive using harmonic injection cannot be applied. Therefore, we apply a position sensorless drive based on Induced Voltage caused by Magnetic Saturation (IVMS) to this motor. As IVMS becomes very small for motors without saliency, we introduce a differential amplifier and adjust its gain appropriately. We implemented this method by using a microcomputer and an analog circuit. As a result, excellent drive performance in a low-speed region was obtained in experiments for the motor (200V/11kW).
Simplified reaction models were developed theoretically and experimentally for use in the computational fluid dynamics of Gallium Nitride (GaN) growth in metal organic vapor-phase epitaxy (MOVPE). The activation energy of various elementary reaction pathways in a trimethylgallium/ammonia /hydrogen (Ga(CH 3 ) 3 /NH 3 /H 2 ) system were calculated using an ab-initio molecular orbital (MO) method. Then, the dominant steps of the reaction paths and the respective activation energies were obtained using the following reactions: Ga(CH 3 ) 3 + NH 3 → Ga(CH 3 ) 2 NH 2 (Ea = 1.3 eV), 2Ga(CH 3 ) 2 NH 2 →[Ga(CH 3 ) 2 NH 2 ] 2 + 2CH 4 (Ea = 0 eV), Ga(CH 3 ) 2 NH 2 → GaN + 2CH 4 (Ea = 3.0 eV). The computational fluid dynamics performed using our reaction-model agreed well with the experimental results for the distribution of the GaN growth rate under this study's growth conditions.
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