Sinamics DCM hunting in current

Hello experts,

I am using Sinamics DCM 6RA80 for rewinder application with 18.5 kw DC motor. The incoming supplies to the drive are from a UPS which is fed from grid power. 

When on Grid power everything is okay. But when we switch on Generator power to the input of UPS (400 KVA), the rewinder motor current starts hunting. (Since the rewinder is in Tension control speed also hunts) Hunting is more than 50 % in both sides.

What can be the problem ?, I checked the Generator Frequency is being maintained at 50 hz and voltage level is also same and stable. Is there anything else I can check ? what can be the probable causes ?

Note : We have similar arrangements in similar machine but with Simoreg 6RA70 but that old model drive remains perfect in the changed scenario also !

I wonder in an upstream sine filter may be necessary to smooth out the UPS pulses, or does the UPS provide smooth sine-wave voltage output on all phases?

PISCEAN 2010

Please check p50152 & p50252 & try by reducing it when drive supply is from generator.

Our UPS, Although a well known brand, doesn't have sine wave filter, 

It is having a converter.and inverter also, but input frequency reflects directly in output without any corrections unless the UPS is on battery backup.

Thanks a lot,

Will check in next opportunity and share the results.

hi

maybe you should have separately two optimization for motor and  it switch between index 1 and 2