The shield strongly attenuates the electric field noise. Core to shield capacitance is added to the stray capacitance, increasing ground currents in the loop. These currents generate a magnetic field. It is important to minimize the area of this loop as far as possible by routing the cable close to grounded metalwork.
A ferrite sleeve around the three power conductors as they leave the drive will help to reduce common-mode noise current. Take all three conductors two or three times through the core. If it runs hot reduce the number of turns.
Note! Not all drives allow the use of a ferrite sleeve around power conductors. Refer to your manuafacturer’s manual for specific applications.
Occasionally, a technician or service person will ask me, "why not just increase the output by increasing the voltage (the current flow) to the motor?" While that may seem logical, increasing the voltage (in effect, creating an overvoltage situation) will not necessarily boost the output of the device. To understand why, you need to become familiar with a physical characteristic called "hysteresis loss."