Traction motor blowers

[blillpers]

I have one quick question about the Polish locomotives. Eu07, Ep09 etc, it's the same on all. When I'm accelerating the cooling fans will start to work harder as the motor amps increase. However, as soon as I increase power into the maximum setting the fans turn off, even though this is when the load is the highest. The same can be heard on the final notch before the second traction motor kicks in. Wouldn't the motors overheat?

I work as a railway dispatcher⁄signaller (not sure what it's called in english, I control the trains from a signal box) in Sweden and have some experience of driving electric locos. On the Swedish Rc locos for example, built between 1960 and 1988, the fans will increase from half to full power when the motor amps goes above about 1000 and then fall back to half power once the amps are below 1000 again. If you put the throttle at max, the fans will go to full power no matter the speed and motor load. But these are thyristor control locos running on AC power so something must be different.

[youBy]

These fans are for resistors used during acceleration. In EU07 or EP09 motors are cooled by fans coupled with converter (shift+x). They are a bit less noisy and work all the time.

[blillpers]

I understand. So at the highest notch and when using field shunt the resistors are completely bypassed and the fans therefore unnecessary?

Should I accelerate with the second highest notch to keep the fans going or is it normal practice to keep the motor amps around the limit until speed is reached?

[kolejarz2009]

On most old electric passenger locos, the highest power notch is the "resistance-free" position, thus not requiring the fans to work. There are two resistance-free positions on the [EU/EP]07,08,09, S and R, relating to how the motors are connected. S - Serial, R - Parallel. In both cases highest positions are resistance-free positions. Exception is ET22 which also has SR in between the S and R, where there are two groups of serial-connected motors connected in parallel.
I don't know about the rest.

@blillpers Yes, correct

EDIT:

@blillpers  It's desired to go resistance-less as quickly as possible, so you don't burn the resistors