This means that the rotor voltages will be higher and currents respectively lower. Thus in the typical ±30% operational speed range around the synchronous speed, the rated current of the converter is accordingly lower which leads to a lower cost of the converter.
The rotor voltages are higher while the currents are correspondingly smaller. Within the ±30% operational speed range around the synchronous speed, this leads to a reduced rated current of the converter, thereby lowering its cost.