No, it really doesn't work like that with electric motors. The power electronics will be configured so that they cannot run in an "overload" situation. Running a motor at 10% FLC doesn't wear it out any less quickly than running at 99% FLC, provided the cooling arrangements etc are working properly.
If you say so. I only worked on the Central for over 10 years so what do I know about it.
The DC motors on 92TS are each 46 kW cont 54 kW one hour rating. That gives you 1472 kW cont / 1728 kW one hour for an 8car train. But a 8car 92TS accelerating draws (I think) 3000 A, which at 630 V line = 1890 kW. A (small) proportion of that load is taken by train auxiliaries, but leaves, say, 1800 kW for traction. 1800 kW is way over the 1472 kW rating, and over the 1728 kW one hour rating, even allowing for the default 9% losses in DC motors. These are DC traction motors, and series wound DC railway traction motors always work in overload zone during acceleration. Full stop. That is how DC motor electric trains work in practice.
Further, arguing that running at 10% underload vice 99% is not the point of debate - what is the point is running at 33% overload vice 100%. Even if you have perfect cooling, your commutator and brushes wear increases, more stress on bearings, and so on. Worn bearing => vibration => impaired commutation, increases degradation.
Or. If you insist, I'll point out that to maintain timetable, 92TS runs flat out, into the overload zone on the performance curve, full motoring then flat out full braking (motors do the bulk braking effort) and if can not overload, to run 8car train with one 2car cut out => 25% traction AND 25% BRAKING effort cut out - you can not maintain point to point run times; ok you only lose a few seconds each run, but on every point to point, which accumulates, and then also this with more than one train (as that is the logical extension of what is suggested) the timetable collapses; the ATO timetable has a resolution of 1 second***, and trains behind the cut out one will start to block back. All day.
So.
EITHER you can't run the timetable with cut out cars (if motors are load capped) or will damage the remaining motors (if motors are not load capped).
Either way. You don't do it. Which is why we don't.
*** a little of which I did some calculations for a mod last decade