First, AC servo's are rarely if ever AC induction motors.
They are predominantly permanent magnet.
Normally if the motor is sufficiently large enough, this may warrant a 3 phase supply to the servo drive, just because a DC supply originating from 3 phase instead of 1 ph is more efficient.
The AC supply, whether 1ph or 3ph is converted to DC and then AC sinusoidal variable frequency and amplitude wave form is produced electronically.
The drive is then controlled by various input methods from the external controller.
Feedback is usually either via encoder or resolver.
The bottom line is, is if the voltage is suitable then the input 3ph power is fine.