A field-oriented control (FOC) method using the virtual currents for the induction motor drive

<span lang="EN-US">An improving field-oriented control technique without current sensors is proposed to control rotor speed for an induction motor drive. The estimated stator currents based on the slip frequency are used instead of feedback current signals in the FOC loop. The reference signals and the estimated currents through computation steps are used to generate the control voltage for the switching inverter. Simulations were performed in Matlab/Simulink environment at rated speed and low-speed range to demonstrate the method's feasibility. Through simulation results, the FOC method using virtual sensors has proved its effectiveness in ensuring the stable operation of the IMD over a wide speed range.</span>

OPTIMIZATION OF USE CONDITIONS FOR CATHODIC ARC NICKEL COATING DOPED WITH PHOSPHORUS

The results of tribological tests for a cathodic arc nickel coating doped with phosphorus are presented. The coating (thickness of 2 μm) is applied by a vacuum arc method from a nickel target with 6% phosphorus. The friction coefficient (Cfr) was determined on the tribometer, the depth of wear h of the coating after tribological tests was determined by the contact profilometry method, and the specific volumetric wear (ω) was calculated. The obtained values of Cfr, ω, and h were used to optimize the parameters of tribological tests (load and slip frequency).

Efficiency Improvement by Deriving the Optimal Operating Slip Frequency of a Linear-Induction-Style Maglev Train

While urban maglev trains have the advantage of being optimized for urban environments where noise is low and dust is less generated, their driving efficiency is low when compared to rotary induction motors owing to the structural limitations of linear devices. To compensate for these disadvantages, various studies on train control schemes have been conducted. Representative control methods include improving the efficiency of using slip frequency by directly controlling the propulsion force using vector control. However, this method has limitations in its use as it relates to the normal force that affects the train’s levitation system. Therefore, in this study, mathematical analysis was conducted for each factor that mutually affects the control of the train. On this basis, the magnitude of the normal force related to the safety of the train is limited. Operating efficiency was improved by varying the slip frequency according to the operating conditions of the train. In addition, for verification, the effect was proved through a comparative experiment using an 18 ton class maglev train running at Incheon International Airport.

Condition Monitoring of Motor-Gear System Dynamics With Rotor and Gear Faults

An electromechanical system consisting of an electric motor and planetary gear set is modeled and analyzed in this paper. The model integrates various internal excitations including time-varying gear mesh stiffness, nonlinear spatial effect and, saturation effect, and component flaws. The simulation results predict the effects of rotor and gear faults including broken rotor bar, rotor static and dynamic eccentricity, and tooth root crack of the gear on the electromechanical system behavior. It is verified as the results obtained are in accordance with the features derived within previous researches. Furthermore, new sidebands merged on the dynamic response spectra such as slip frequency harmonics, rotor rotational frequency harmonics, and fault-related rotational frequency harmonics can be applied to detect electrical and mechanical faults in the motor-gear system. This paper lays the foundation for the comprehensive further study of working condition monitoring for the motor-gear system.