Looking at power handles on electric multiple units, I notice in cab pictures that almost all modern electric units (even Pendolinos!) have 5 notches 0, 1, 2, 3, 4 (with Siemens Desiro units having an extra notch). This seems to be true both for separate power handles and combined power and brake controllers.
At first sight this looks like the old control system for dc motors using pneumatic cams for automatic acceleration - OFF / Shunt / FULL SERIES / FULL PARALLEL / WEAK FIELD.
However, I am pretty sure that nothing built after 1990 used such a system. Mostly AC motors now and solid state control. So why the notches? Are they equivalent?
I would expect Notch 1 would give minimal power for shunting, but beyond that how does it work?
Do all the notches offer automatic acceleration? (Simply corresponding to different maximum power outputs or speeds). Or do you have to "notch up"? Do different notches provide different rates of acceleration? (For different conditions of adhesion).
At first sight this looks like the old control system for dc motors using pneumatic cams for automatic acceleration - OFF / Shunt / FULL SERIES / FULL PARALLEL / WEAK FIELD.
However, I am pretty sure that nothing built after 1990 used such a system. Mostly AC motors now and solid state control. So why the notches? Are they equivalent?
I would expect Notch 1 would give minimal power for shunting, but beyond that how does it work?
Do all the notches offer automatic acceleration? (Simply corresponding to different maximum power outputs or speeds). Or do you have to "notch up"? Do different notches provide different rates of acceleration? (For different conditions of adhesion).