Voltage drop in motor starting

Whatever voltage drop you settle on, you need to consider a number of important factors:
The torque output of the electric motor will reduce by the square of the voltage drop (90% voltage to the motor terminals will result in 81% of the motors rated output torque to the mechanical load). In this reduced torque situation, if the pullup torque is less than the load torque the motor will stall. I have been faced with this scenario a number of times; one where the supply transformer was too small resulting in large Volt Drop when restarting a loaded conveyor, and another application where the run up time on a soft starter was set too long. Soft Starters are reduced voltage starters where the initial voltage applied to the motor may be 30 to 40% of rated supply voltage.

Generally when we design for voltage drop it is for steady state conditions not starting current. If you are going to cable you plant to control Volt Drop on motor starting you will never afford to construct a plant and remain competitive in business.