Chopper Coil failure in seguvanthive and vidathamunai

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Chopper Coil failure in seguvanthive and vidathamunai

Post by Aravinda on Sun May 15, 2016 10:27 pm

This Discussion is relevant to the chopper coil failure in Made machine By GAMESHA in Our Seguvanthive and Vidathamunai Wind plants. An under develop fault tree on the matter is showing below.



A coil to be failed
1. Insulation have to fail
2. Over current have to flow.
At the moment where the document is preparing, the current scenario is kept a side because normally the current inside the inductor is measuring continuously with a high frequency by the control system of the full converter setup. Even though over current is possible due some destruct of switching device or faulty switching, it is not the initiator.



The diagram is showing the overall setup of the Conversion, chopping and the inversion. 2T1 is the Chopper inductor. The voltages of bi the sides of the 2T1 is not defined relative to the ground (floating). Normally this coil must withstand for the operation voltage including switching surges. Otherwise it will fail it the operation. So it should have the required insulation. The maximum stress available in this coil is at the two ends of it.
It is worthy to improve the insulation, because it may already have deteriorated the insulation with the time and also it may not enough for our harsh environment (Saline atmosphere and high heat).
But if we assume the insulation is ok for a normal operation, at a lightning situation there is a possibility of over stressing the insulation between ground and coil. In addition the electric field can initiate a miss fire of the switch. In such a satiation (miss fire) the building voltage across the coil may be unexpectedly higher than normal.
Sometimes the improving of insulation in chopper coil may cause a diversion of the stress in to next element. Here it may be Diode (4V1), Reservoir capacitor (4C1) or the Chopper IGCT (IGCT7).
There is a possibility of applying Surge arrestors for the incomer side of the convertor (as our TO suggested once).
Further discussion on this matter is required for trying some solution. However it is better if we can consult an expert in this matter, to get a clarification and a recommendation.
The discussion is fully open for comments." />

Aravinda
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