Why Moisture In Explosion Proof Motors ?

Let me know why we found moisture usually inside the Motor body when dismental for maintenance even specification is EEx de II C T4, IP 55.

FLASH OVER INSIDE THE VSD BUT WHY ???

Hi there! I hope someone will be able to assist me about reasons & possible causes of flash over. I work at a Gas plant in Pakistan. Our plant commissioned just two year before in 2002 , there are many VSD installed but last week a ABB VSD to drive an induction motor 37 KW its service was Produce water disposal pump flash over found inside the VSD so due to flash main PCB ( we can say mother board ) found severe damaged. We are now trying to establish the cause for this. VSD mounted on the wall in the air conditioned switch room but not IP protected. On inspection / checking I found that the cooling air fan working normal. Do you have any ideas ? Thank you for your assistance.

Lock rotor current & Short circuit current

I want to know the defination of lock roter current & short circuit current ? Any body can explain me through practical example / through graph or curve?

Diffrence b/w VSD & Soft starter ?

I want to know that what is the diffrence between Variable Speed Drives and Soft Starters ? Define basic diffrence in short please ?

Any web site to view E-Tap software ?

( 1 ) I want to see any kind of software which is used to short circuit calculations, just like E-Tap or other?
( 2 ) If any body knows electrical power system calculation software , which help us to find any one i.e volt / ampere / watt / rpm / frequency / kwh / KW / HP / Poles / Resistance & other parameters related to electrical system, or any site which help me to find out that problem?