Answer / ravi

Protection of S.M Above 12 MW:-

The Best Protection method is by SPM:-

Application of SPM Protection:-

• Field application
• DC field current loss, exciter current loss, DC field
voltage
check

• PF regulation, reluctance torque synchronizing
• Protects motor during start up and in the event of
asynchronous operation
• Squirrel cage winding overheating protection
• Automatic phase rotation correction
• Auto-loading and incomplete sequence
• Regulator tuning mode
• True RMS metering with DFT filtering
• Optional power factor regulator with adjustable settings
• Power factor & pull out protection (Optional)
• Speed dependent squirrel cage overload protection
• Motor restart protection

WHEN THESE TRANSFORMERS WINDINS CONFIGURATION ARE USED? SPECIALLY EXPLAIN REGARDING STEP UP AND STEP DOWN KEEPING IN MIND.AND REGARDING LOAD ALSO. a.star to delta b.delta to star c.delta to delta d.star to star ALSO EXPLAIN WHY V USE 415/415 TRANSFORMERS IN TUBEWELLS?

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generally in LT and MV motors we are using 3.5Coresx16,25,35,50 etc cable for supply.although motors is earthed at two point and having all protection.then why we are using that 1/2 core for earthing the motors.while in HT cable we are using only 3core cable for motor supply.generally lt and mv motors are delta connected and ht motors having star connection.whethere it is having any relation with winding connection( star or delta).all motors i am talking about are dol only.can anybody solve my confusion.thanks...

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