When the motor is controlled by a variable speed drive (VSD):
1>> The current transformers (external or internal) must be mounted upstream of the variable speed drive, and not between the variable speed drive and the motor. The CTs cannot be used between the drive outputs and the motor because the drive can output fundamental frequencies outside the 47-63 Hz range.
2>> Chokes must be mounted on the three phases, between the current transformers (external or internal) and the variable speed drive, to minimize the soft start harmonics current and the voltage disturbances generated by the variable speed drive

Released for:Schneider Electric India