Length of time for LRA is dependent on the total mass of the load being turned and or if something is being started under a load or not. On some of the bigger motors I've seen the current take anywhere from a second or so, on up to to 4 or so seconds until the motor reaches the FLA. During that time period from LRA down to FLA, the current is decreasing the entire time....but it will definitely catch your attention when you see the ammeter jump up to say 700 amps at 4160V, and the normal current reading my be 110, 115 amps.How long would you guess that LRA amperage stayed high or tapered off until the normal run amperage kicked in?
On those high voltage motors you mentioned would you have to adjust cable size for the excessive LRA?
As far as adjusting the cable size for the LRA....I don't know. I was never involved in any of the engineering or design end of it. The motor protection OL (overloads) must be fine tuned though to be able to withstand that type of current and take into acct. the time delay before it reacts and opens the circuit, taking the motor off line if either current or time is exceeded. Those are fairly expensive devices, just like you would expect in an industrial setting.