I am listed on Chartered Consultant Dr Antony Anderson C.Eng  FIEE Electrical Fault & Failure Investigations General Capability Statement on electrical fault investigations List of Recent Electrical Fault and Other  Investigations Previous investigations: Generator Core Failures A Note on Generator Core Failures  With video demos of simulated interlaminar breakdowns References on aspects of Generator Core Faults / Core Failures   Automatic Cruise Control Problems in Automobiles LeBlog Auto: Electronique embarquée: l'analyse d'un expert indépendant Articles by Antony Anderson on the lessons to be learnt from failure:  A  Museum of Failure [New Scientist 8 June 1991] Lessons from disaster [New Scientist : 5 June 1993] Making a success out of failure  [EM Journal April 2001] enlarged picture from Paper on interlaminar breakdowns in large electrical machine motor armature failure

Recent electrical fault and other  investigations carried out by Electrical Consultant Antony Anderson : intermittent faults on Substation Air Circuit Breaker Control Unit [UK]**; catastrophic armature failure of a 1300 kW variable speed D.C.motor [UK]*; anomalous hotspots arising during flux tests on a rebuit hydro-generator stator [North America]; interlaminar breakdowns  on a 30MW generator core and advising on in-situ repair [North America]; in-service stator winding failures on deep well pump induction motors [Libya]; intermittent tripping of induction motors during star-delta starting [UK]; questionable performance claims for an electrostatic generator; [UK]; electromechanical problems and motor reliability in a dispensing machine application; [UK ]*; in-service winding failures on switched reluctance motors  [Benelux ]; patent aspects of switched field reluctance motors [UK]; advising a well known Scottish contract R & D laboratory specialising in electrical machine problems [UK];   alleged electric shock from an electric lift call button (electrostatic charging) [UK]*; alleged  electric shock to a maintenance technician working on a vacuum forming press. [UK]*; Possible causes of vacuum cleaner fire that resulted in operator injury [UK]*; Possible causes of an automobile electrical fire [UK]*; alleged vehicle instability caused by electrical connector malfunction; [UK]* ; automobile cruise control problems  [UK, USA, France] [note] * * Electrical Expert Witness  ** Single Joint Expert

Previous Investigations : Generator Core Failures When Antony Anderson  was Group Leader of the Electromagnetics Group, R & D Laboratories NEI Parsons, he was responsible for managing an inter-disciplinary team that  investigated a number of generator core fault and core end heating problems. These investigations had to be carried out thoroughly but with minimum interference with repair programmes.  He also was responsible for coordinating the programme of instrumentation and measurement of flux, temperature, interlaminar voltage and eddy currents in generator stators. He therefore has considerable investigative experience to offer on problems associated with large electrical machines. For commercial reasons, only a small proportion of this work was ever published.  Further information related to generator core faults will be found under: A  note on generator core failure mechanisms References on aspects of Generator Core Faults (Below on this page)

       

References on aspects of Generator Core Faults / Core Failures Tavner, P.J., Anderson, A.F. :  Core faults in large generators  IEE Proceedings - Electric Power Applications -- November 2005 -- Volume 152, Issue 6, p. 1427-1439 Abstract. A core fault is a failure in the laminated core of a large electrical machine. Such faults are relatively rare but when they occur, the value of the machine and its importance mean that the investigation of the failure assumes a high priority. On many occasions the details of such failures assume major commercial significance, therefore failure investigations have, of necessity, to be handled in a confidential manner, touching as they do on the design, manufacture, operation and insurance of large electrical plant. There has therefore been no published literature on core faults. However, the scientific principles of the mechanisms at work have been studied in considerable detail and papers published on those principles in the international literature. This paper brings together that literature and those scientific principles, giving details of the underlying design, constructional and operational factors which affect these faults. New evidence is presented of the underlying factors which allow core faults to initiate and grow. The paper will allow engineers to analyse such faults, draw rational conclusions on the causes for each occasion and devise suitable repair/rebuild strategies applicable to that situation. [PDF copies of this paper can be purchased from the  IEE]  [In the event of any difficulties, contact Antony Anderson .]   Le Ny, R. Guile, A .E., Anderson, A. F. : Mechanism of "Meandering" Breakdown of Insulation in an Electrical Machine. Proceedings of First International Conference on Conduction and Breakdown in Solid Dielectrics. Université Paul Sabatier TOULOUSE -France July 4-8, 1983 Paper H9 p. 395-398.    SEM photograph of the head of a meandering  breakdown showing wavefront of transiently  melted core varnish ahead of the meandering breakdown. Abstract: A Scanning Electron Microscope examination of the head of a meandering interlaminar breakdown suggests that a repetitive arcing process has been occurring between the laminations and that the cause may be a series of high voltage pulses caused by current chopping.  Platt, R., Kerr, L.C., Anderson, A. F. :  Measuring Flux and Interlaminar Voltage in Turbine Generator End Regions. Int. Conf. Electrical Machines - Design and Applications IEE London 13-15 July 1982 p. 201-205    Back-of-core leakage flux in large turbogenerator Abstract: This paper describes the general approach to the measurement of flux and interlaminar voltages in turbogenerator end regions.Construction and locations of typical search coils are shown. Some selected results of measurements of interlaminar voltages in the end region are given which show typical values of 5v peak-to-peak at 50 Hz. The induced voltage in a back-of-core search coil at the core end is shown to rise sharply under short circuit conditions, whereas in a similar coil well away from the core end the voltage collapses. As far as is known, this paper records the first occasion on which attempts were made to measure transient back-of-core flux leakage phenomena on  a large electrical under sudden short circuit conditions. Anderson, A. F., Bedford, T., Craddock, A. F. Transient leakage flux in small universal motors. IEE PROC., Vol 128, Pt. B, No 5, September 1981 p. 254-254   Transient  Back of core leakage flux  in small universal motor Abstract: This communication reports an investigation into the transient back-of-core flux that arises in a small universal motor during start-up. A substantial back-of-core leakage flux was  shown to exist under starting conditions (35 mT peak radial flux density on the direct axis and 14 mT on the quadrature axis) which was caused by excess field ampere turns saturating the core and forcing the flux into the back-of-core region. A standard portable electric drill demonstrated the back-of-core leakage phenomenon to a remarkable degree : attracting to itself under starting conditions a piece of thin sheet steel from a distance of about 20mm. Comment : Whilst the conditions were admittedly very far from those existing in large AC machines, the experiment shows that transient leakage  flux cannot be ignored even in fractional HP motors. The transient leakage flux is quite sufficient to advance the movement of a quartz watch placed in close proximity to the drill casing by several seconds when the drill is switched on. Anderson A. F., Steel, J.G, Reece, A. J. B., Carpenter C.J., Preston. T. W., Phemister, T.G., Smith, R., Hammond, P., Jackson, R. J., Tavner, P.J., Penman, J., Stoll, R.L., Lorch, H.O., Howe, D. : Contributions to 'Discussion on Interlamination voltages in large Turbine Generators and Influence of winding design on the axial flux in laminated-stator cores and Examination of flux distribution in segmented stator cores'  IEE PROC, Vol 127, Pt. C. No2 March 1980 p 114-115.  Abstract : Wide-ranging discussion touching on interlaminar voltages and core failures in which substantial interlaminar voltages in the core end regions are agreed to exist. Spit marks on stator teeth under examination prove to have been micro spot welds requiring interlaminar voltages of at least the so-called melting voltage of iron of 0.6V to have been reached. Calculations by one manufacturer suggest interlaminar voltages in the end regions under steady state conditions of more than 1V. It is suggested that radial back-of-core fields and axial fields contribute approximately equally to interlaminar voltages in the end regions and that the interlaminar voltages will rise during pole slipping. Measured results of interlaminar voltage in the end half metre of a generator core give a mean interlaminar voltage of 500 mV, whereas towards the end of the machine individual interlaminar voltages as high as 4000 mV have been measured.  Anderson, A. F., Guile, A. E. : An unusual type of interlaminar breakdown found in an electrical machine. Sixth International Conference on 'Gas Discharges and their Applications' Heriot-Watt University: 8-11 September 1980    Meandering breakdown Spot weld   interlaminar  breakdown Abstract: A specatacular example of a 'meandering breakdown' between laminations comprising fine filaments of melted steel is described and is contrasted with a much more typical example of an interlaminar breakdown that resulted in a circular spot weld. Metallurgical examination of the filaments showed that there had been very rapid cooling at perhaps 1000 degrees C per second between 1200 degrees C and 200 degrees C. Further evidence of the fast transient nature of the heating and cooling is that varnish can be seen to lie almost undamaged closely alongside these filaments. The authors conclude that the breakdown has some of the features of moving arcs, but some distinctive features of its own. Whilst the mechanism of formation remains obscure, interlaminar voltages of at least 18 volts would appear to be required.