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We prospectively compared, according to their preoperative clinical profiles, the in-hospital outcomes of patients operated on consecutively (but without randomization) for isolated coronary artery disease with on-pump or off-pump techniques. During 2001, 324 patients underwent coronary artery bypass grafting: 216 patients (mean age, 66.7 +/- 8.9 years; range, 41-85 years) underwent on-pump revascularization, and 108 patients (mean age, 676 +/- 10 years; range, 37-90 years) underwent full-sternotomy off-pump revascularization. The 2 groups were homogeneous with regard to female sex (22.6% vs 26.8%), previous cardiac operation (2.8% vs 4.6%), cardiogenic shock (1.3% vs 1.9%), diabetes (30% vs 33%), and chronic renal failure that required hemodialysis (3% vs 3.5%). Postoperative complications, including bleeding, myocardial infarction, acute renal failure, mediastinitis with sternal dehiscence, cerebrovascular events, and prolonged respiratory assistance were more frequent in on-pump patients (P = 0.004). The total number of grafts and the grafts per patient ratio were significantly higher in on-pump patients (P = 0.0001), whereas the total number of full arterial revascularizations was higher in off-pump patients (P = 0.0001). Off-pump patients showed a significantly shorter intensive care unit stay (P = 0.02), and less need for intra-aortic balloon pump insertion (P = 0.04). In-hospital mortality was 2.8% in on-pump patients and 2.7% in off-pump patients (P = NS). Although the hospital mortality rate was comparable for the 2 techniques, the in-hospital comparison between the 2 groups showed how the avoidance of cardiopulmonary bypass can significantly reduce the cumulative postoperative incidence of complications in patients undergoing coronary artery bypass grafting.

Rotary assembly stations are commonly used in automated manufacturing processes. These production platforms require the speed control of the plate and need power for the actuators and sensors located on the rotating frame. These requirements are usually met through a gearmotor and sliding electrical contacts. Among the solutions that avoid the slip-rings, this paper focuses on an integrated electric drive consisting of a gearless five-phase wound-rotor induction machine fed by two inverters, one placed on the stator reference frame and one placed on the rotating one. The main contribution is a novel control scheme that maximizes the power transferred to the rotating loads in compliance with the thermal constraint of the rotor and the voltage constraint of the rotor inverter. The theoretical analysis allows deriving an analytical solution to the control problem, and the experimental results confirm the effectiveness of the proposed algorithm.

Multiphase induction motors are receiving more and more interest in applications where safety and high reliability of operation are key items. Thus, condition monitoring of stator faults is crucial for guaranteeing high motor performance and efficiency. In this paper the behavior of an asymmetrical twelve-phase induction motor, with quadruple three-phase winding configuration, is investigated under high resistance connections affecting the stator windings. The analysis leads to a simple and effective methodology for detecting and localizing stator high resistance connections at incipient stage. The proposed approach is based on the computation of the voltage space vectors evaluated in the available four α-β planes. The performance of the proposed strategy is confirmed by means of numerical simulations.

This article presents a postfault control algorithm that minimizes the stator Joule losses in multiphase induction machines under an open-phase fault and for different star connection layouts. The key novelty is that the algorithm can be applied to any configuration of a multi- n -phase machine, independently of the connection of the neutral points. The latter is analytically derived and is based on the space vector representation of the machine model. In addition, it is shown that a low number of neutral points helps to reduce the winding losses in case of an open-phase fault but requires additional control regulators and computational efforts. The theory is applied to an asymmetrical quadruple-three-phase induction machine, which is configured to represent five different motor layouts. Finally, experimental results are presented to validate the control algorithm. The optimal solution that is given in this article can be employed for the control of symmetrical or asymmetrical multiphase machines with different star connection layouts and in any open-phase postfault operation.

In three-phase electric drives, overmodulation is commonly used to fully exploit the dc-bus voltage, increase the dynamic performance of the motor, and reduce the inverter switching frequency. The same advantages can be found in multiphase converters, where a higher number of degrees of freedom allows defining new operating modes. In this article, the extension of the overmodulation strategies of three-phase inverters to five-phase systems is investigated. Experimental tests on a five-phase induction motor drive are carried out to verify the feasibility of the developed techniques, the quality of the current waveforms, and the improvement in the dynamic performance of the drive.

In the last decade, the interest for higher reliability in several industrial applications has boosted the research activities in multiphase permanent magnet synchronous motors realized by multiple three-phase winding sets. In this study, a mathematical model of an asymmetric surface-mounted six-phase permanent magnet synchronous motor under high resistance connections was developed. By exploiting the intrinsic properties of multiphase machines in terms of degrees of freedom, an improved field-oriented control scheme is presented that allows online fault detection and a quite undisturbed operating condition of the machine under high resistance connections. More specifically, the proposed strategies for online fault-detection and fault-tolerance are based on the use of multi-reference frame current regulators. The feasibility of the proposed approach was theoretically analyzed, then confirmed by numerical simulations. In order to validate experimentally the proposed strategies, the entire control system was implemented using TMS-320F2812 based platform.

An array of proportional-resonant regulators is often used in shunt active power filters to control the grid currents and reduce the harmonic distortion caused by a distorting load. The voltage that is necessary to compensate for the current harmonics must be consistent with the available dc-link voltage. In this article, three adaptive algorithms for the exploitation of the dc-link voltage are developed and compared. These algorithms adaptively change the voltage saturation of each regulator to preserve the control capability of the fundamental component of the current when the available voltage is not enough to control the filter current. Simultaneously, they try to improve the quality of the grid current because the dc-link voltage of the active power filter is allocated to the regulators to compensate only the most significant harmonics. Some experimental results are shown to demonstrate the feasibility of the three algorithms.

Multiphase permanent-magnet synchronous machines (PMSMs) are receiving more and more interest in safety-critical modern industries owing to their higher reliability when compared with conventional three-phase PMSMs. Rotor magnets are critical components, which, in case of fault, directly affect the performance of the PMSMs. Thus, monitoring the rotor magnets status is essential to ensure both high level of efficiency and service continuity. The present study focuses on the investigation of a new approach for the detection of rotor magnet demagnetisation in a vector-controlled asymmetrical six-phase surface-mounted AC PMSM. The main contribution of the proposed technique is the assessment of a rotor demagnetisation fault index derived from the fifth and seventh harmonics of the stator voltage space vector evaluated in the α 5–β 5-plane, and already available in the control system platform. The performance of the proposed approach is evaluated using finite element analysis and numerical simulations, both validated by experimental tests.

This paper illustrates the control system of a five-phase wound-rotor induction machine that can be used in applications where, besides the torque generation, a certain amount of active power must be transferred to loads collocated on the rotor frame. This requirement is common in rotary assembly platforms, bottle filling and capping systems, that embed electric actuators, sensors and process controllers on a rotating disk. The use of a five-phase machine avoids the slipring contacts to feed the rotor load. However, the choice of the set-point values for the motor currents involves magnetic, electric and thermal constraints. The paper illustrates a methodology of analysis, and develops a technique to deliver power to the rotor loads through the third-order spatial component of the magnetic field, while keeping the motor torque under control and reducing the rotor current as much as possible to minimize the rotor Joule losses. The experimental tests on a scaled prototype demonstrate the practical potential of the machine.

Background: Gastroparesis is a digestive syndrome characterized by delayed gastric emptying (GE) and by symptoms that are suggestive of gastroduodenal motor disorders. There are three grades of gastroparesis of increasing severity: (a) mild gastroparesis; (b) compensated gastroparesis; and (c) gastric failure. GE abnormalities are partially related to symptom type and severity, and other mechanisms may be involved. Aim: To investigate enteric dysmotility (ED) in patients with suspected gastroparesis. Methods: Patients with symptoms suggestive of gastroparesis were consecutively included in the study and underwent a 13 C-octanoic acid GE breath test and small bowel manometry (SBM). Clinical features were recorded using predefined, validated questionnaires at entry. Key Results: The study enrolled 88 patients (71 women; mean age: 37.8±14.3years). Gastric emptying was delayed in 25 patients (28.4%), and 70 patients (79.5%) presented small bowel motor abnormalities including bursts, abnormal activity fronts, inability to respond to meal ingestion, and hypocontractility. Gastric emptying was delayed in 24 of the 70 patients with ED (34.3% vs 5.5% of patients with normal SBM). Enteric dysmotility was detected in 24 of 25 patients (96%) with delayed GE. Patients with and without delayed GE showed similar moderate/severe gastroparesis manifestations, but patients with ED significantly more often had moderate/severe gastroparesis manifestations than patients with normal SBM (grade 1:14% vs 39%, grade 2:62% vs 56%, grade 3:24% vs 5%, respectively). Conclusions and Inferences: Enteric dysmotility was more frequent than delayed GE in patients with symptoms suggestive of gastroparesis. Gastroparesis severity was associated with small bowel motor abnormalities but not with delayed GE.

The matrix converter rectifier is an AC-to-DC converter that can be considered for emerging applications, related to smart grids and renewable energy production. The most attractive characteristics of this converter are the simultaneous control of the input power factor and the output voltage, and the small volume of the input capacitors. In this paper, after a small review of the modulation techniques, several modulation strategies are experimentally compared in terms of power losses and THD of input and output currents.

Various soft switching inverter topologies have been reported in the literature with the aims of reducing the switching losses and dynamic switching stress. However, lower losses are generally regarded as one of the most significant advantages of the emerging silicon carbide semiconductor devices over the conventional silicon devices. Both routes seem viable to improve the converter efficiency. To investigate the optimal solution, this paper experimentally evaluates the efficiency of six prototypes, i.e., three zero-voltage transition inverters differing only in the power switches, and three hard-switching inverters, mounting both silicon and silicon carbide devices. A set of experimental results is included.

A speed control scheme is proposed for a 3-phase induction motor that uses an open-ended stator winding fed by a dual inverter system with a floating bridge. The floating bridge has a voltage boosting function that extends the constant power high-speed range of the induction machine and operates the main inverter bridge at unity power factor. The proposed control scheme coordinates the two inverters that supply the motor, regulates the dc-link voltage of the floating bridge and boosts the machine terminal voltage at high speed. Simulation results are used to clarify the motor-drive torque capability in the high speed region. Experimental results show that a significant power improvement is achievable in the field weakening region.