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Partial discharge simulation in large scale turbo&gas generators using acoustical FEM.

Kourosh presented a micromachined electromechanical acoustic senor to wrap around Roebel bar of generators, October 17, Bergen, Norway. 
A micromachined piezoelectric multi sensor together with Hall Effect magnetoresistive sensor that can be used with piezoelectric sensor to verify results are used to PD monitoring.
It is wrapped around the final insulation or conductive tape of Roebel bar or semi conductive around overhangs.
These sensors together with a pro system enable continuously to monitor PD.

KOUROSH presented an acoustical diagnostic routine that is focused on insulation faults of gas-turbo generators. Finite element method (FEM) has been used to model a void in bar insulation. Constant pressure is assumed for void. When partial discharge (PD) occurs, propagated sound energy in stator and surrounding air is simulated. Acoustic sensors can distinguish between slot discharge and internal coil PD, but they may do not discriminate between positive and negative pulses.

Simulation shows the released sound from a PD pressure source strongly influences in core sheets but it gets weak when arrives to air gap or surrounding air. It means most of the energy released by PD is detectable with installed piezoelectric sensors which are placed across each slot or locally mounted on the stator. Sensors placed underneath the wedges or between bottom bars and slots, can easily find the PD locations. When used together with electromagnetic probe, piezoelectric sensors are reliable for pinpointing sites of high PD activity, such as slot discharge.

For system modeling a Mitsubishi 85 MW, 11 kV gas-generator is used. Broken tooth caused this generator to trip. One of our diagnoses for this trip is PD occurrence in slot.

FEM simulation for the discharge processes has been developed. A model simulates sound energy in void. Simulation shows sound pressure is limited to the PD point and is not affected by environmental acoustical noises, around the bars.

Results are presented, discussed and published in SIMS2012, Reykjavik, Iceland, 3 October 2012.

Process control and simulation of ferromagnetic strips

Thickness of strip in the cold rolling mill during each pass of thickness reduction is measured by X-Ray method. Instruments are installed two meters down stream of work rolls. It makes delay to actuate of hydrulic actuators. About 30 Sec delay in low speed travling strips lead to un accurate thickness and deviations. Six micrometers deviations is the average of those. BIARSA Model and Smith pridictor devices could not overcome on this mentioned delay problem.

Kourosh´s presented model is the newest Offline- Online method to controll of RGC in rolling of ferromagnetic strips. ANN method  used to model the system. BP with LM traning method and intelligent learining rate tuning were used to model the cold rolling mill. Weights of ANN model calculated and the model verified by measured data throgh the automation system. It overcomes on delay problem and can estimate thickness between work rolls, precisely.

Models, control system block diagram, simulated and measured data are shown in the following figures:


  بزرگترین سد بتونی / دوقوسی خاورمیانه در شهر زیبای ساری ، قلب تپنده ایران بزرگ واقع شده است  . این سد در 45 کیلومتری جنوب ساری و 20 کیلومتری روستای تاریخی تاکام(مابین ساری وسد) واقع گردیده است.

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