Design, Production and First Commissioning Results of the Electrical Feedboxes of the LHC

A total of 44 CERN designed cryogenic electrical feedboxes are needed to power the LHC superconducting magnets. The feedboxes include more than 1000 superconducting circuits fed by high temperature superconductor and conventional current leads ranging from 120 A to 13 kA. In addition to providing the electrical current to the superconducting circuits, they also ensure specific mechanical and cryogenic functions for the LHC. The paper focuses on the main design aspects and related production operations and gives an overview of specific technologies employed. Results of the commissioning of the feedboxes of the first LHC sectors are presented

Design, production and first commissioning results of the electrical feedboxes of the LHC

A total of 44 CERN designed cryogenic electrical feedboxes are needed to power the LHC superconducting magnets. The feedboxes include more than 1000 superconducting circuits fed by high temperature superconductor and conventional current leads ranging from 120 A to 13 kA. In addition to providing the electrical current to the superconducting circuits, they also ensure specific mechanical and cryogenic functions for the LHC. The paper focuses on the main design aspects and related production operations and gives an overview of specific technologies employed. Results of the commissioning of the feedboxes of the first LHC sectors are presented

Is diagnosing exposed dentine a suitable tool for grading erosive loss?

Quantifying tooth wear in general and erosion in particular mostly is made by distinguishing between lesions restricted to enamel and lesions reaching the underlying dentine. Various scores for grading have been used, but in all systems, higher scores are given in cases of exposed dentine, thus, indicating a more severe stage of the condition. Clinical diagnosis of exposed dentine is made by assessing changes in colour or optical properties of the hard tissues. This paper aims to review the literature and discuss critically problems arising form this approach. It appears that classifying the severity of erosion by the area or depth of exposed dentine is difficult and poorly reproducible, and taking into account the variation of enamel thickness, the amount of tissue lost often is not related simply to the area of exposed dentine. There has still been very little longitudinal investigation of the significance of exposed dentine as a prognostic indicator. Further work and discussion is needed to reevaluate the explanative power of current grading procedures

Investigation of vibration spectrum of three-phase induction motor at stator winding damages

The paper deals with the diagnostics of windings damages in three-phase induction motors basing on the machine vibration analysis. By means of the computer program, the vibration spectrum has been analysed and the essential diagnostic harmonics of vibration of the three-phase slip-ring induction motor were chosen. The following damages: the internal short-circuit of the winding to the frame, the internal shorting between two phases and the shorting of the stator coil have been investigated. Within the comparative diagnostics, the data of the symmetrical three-phase induction motor are the basis for a state valuation of the machine. It was shown that the change of vibration spectrum can correspond with the technical state of the motor. The extended strategy of vibration research is connected with measurements for frequencies of a wide range. In this paper, the acceleration amplitude has been taken into account for the assessment criterion and thanks to this choice vibrations of great frequencies were more visible. Measurements have been done for the motor placed on the work-stand

Analysis of acoustic spectrum of three-phase induction motor at stator winding damages

The paper concerns the diagnostics of windings defects in three-phase induction motors basing on the electric machine noise analysis. With the help of the computer software, the acoustic spectrum was analysed and the dominant diagnostic harmonics of noise of the three-phase slip-ring induction motor have been determined. The failures of the following type: the internal shorting between two phases and the short-circuit of the stator coil have been investigated. The problem of the increase of the damage degree was also analysed. Within the framework of the comparative diagnostic methodics, the properties and parameters of the symmetrical three-phase induction motor are the basis for a state valuation of the electrical machine. It was illustrated that the change of the acoustic spectrum can give information about the technical state of the motor. The interesting methodology of noise research consists in investigations for frequencies of a wide range. All presented in this paper measurements have been done for the three-phase induction slip-ring motor placed on the work-stand