Motor Starting Studies 1

[edetaen]

I have a peak Load of about 33Mw(at 11kV) and wish to use 3 GTGs rated 12.9Mw with an alternator of 15Mw with 3+1 philosophy included these Loads are
XHP Flash gas Compressor-2Mw
HP Flash gasCompressor-2Mw
LP Flash gasCompressor-1Mw
Surge vessel Flash gas0.8mW
All on electric drives we have run the Motor starting studies using ETAP the motors did not run on VFSs but run on softstarter.
But i m not so cofident that these motors should be able to run on electric drives.Please any advice will be appreciated

 

[krisys]

I understand VFS stands for Variable Frequency Starter. If my understanding is correct, the dive characteristics is comparable with variable Speed Drive (VSD or VFD, where F stands for frequency).

The major difference is the VFS is sized for a very short time duration. Additionally, the controls are limited. Thus the physical size of the VFS is less compared to the VFD of same rating.

For the VFDs the motor starting study is not required, as the starting current is limited to 100 % (in some cases upto 110%)of the full load rated current.

Hence in my view only the load flow should indicate the system voltage drops, even during the starting.

 

[edetaen]

But also i have run the system on on VFD even though the compressors are starting at 110% the compressors are not running on full load current ie cannot achieve max spin on if VFD is adjusted to 250% which is unconventional