16 research outputs found
IPMSM Model Including Magnetic Saturation and Cross-Coupling
This paper presents a modified IPMSM model suitable for use with carrier-signal-injection-based sensorless methods. The suggested model includes magnet saturation of both d- and q- axis and cross-coupling which all result in more accurate description of high frequency test signal propagation. The model is verified by comparing experimental results of a sensorless method based on HF test signal with simulation results from standard and modified model
Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)
Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic
Energy Efficient Control of High Speed IPMSM Drives - A Generalized PSO Approach
In this paper, a generalized particle swarm optimization (GPSO) algorithm was applied to the problems of optimal control
of high speed low cost interior permanent magnet motor (IPMSM) drives. In order to minimize the total controllable
electrical losses and to increase the efficiency, the optimum current vector references are calculated offline based
on GPSO for the wide speed range and for different load conditions. The voltage and current limits of the drive system
and the variation of stator inductances are all included in the optimization method. The stored optimal current vector
references are used during the real time control and the proposed algorithm is compared with the conventional high
speed control algorithm, which is mostly voltage limit based. The computer simulations and experimental results
on 1 kW low cost high speed IPMSM drive are discussed in details
Automated Method for M-curve Signature Measurements of RR Devices and Modules
In this paper we describe an automated method for testing the influence of selective fading on a radio-relay system and its vital modules in the form of M-curve signatures. Presented method is developed with a goal to make efficient measuremets of different RR devices generations, as well as to enable effective R&D of new RR equipment