Yes, I agree with the above. The power dissipated in the rotor is dependent on the load inertia for a purely inertial system. There is additional power dissipated in the rotor due to the work torque required during acceleration. With a purely inertial load, the total power dissipated in the rotor shold be the same for full voltage or reduced voltage starting, just the rate at which it is dissipated changes with start voltage.
With a load requiring work torque during run up, provided that the acceleration torque is significantly higher than the work torque during start, the increase in heating will not be significant. If the acceleration torque is small relative to the work torque, then there will be a major increase in the rotor dissipation and corresponding reduction in number of starts per hour.
In Laymans terms, if the motor accelerates freely and easily under the reduced voltage condition, you will not get a significant increase in heating. If the motor is struggling to accelerate, then the heating will be increased. As was stated above, it is dependant on the setup of the starter relative to the motor and load.
The setings must be such that the motor imediately begins to spin. Some ramp systems I have seen, have a period of time before the voltage ramps up high enough to break the machine away, and that is unecessary heat.
There is an argument that due to the lower rate of dissipation with reduced voltage starting, the heat has time to dissipate through the iron of the rotor, allowing a greater overall dissipation. I am not convinced either way, but would epect less hot spoting in the bars and that could be significant.
Best regards,
Mark Empson