How to correctly read the nameplate of a Bitzer motor
A motor designed for part-winding start has two identical windings. To start the motor, one winding is connected directly to mains power. After a short delay, the second winding is also connected directly to mains power so that the two parallel winding act as a single winding.
The starting current for the first winding is less than the current would be if the two parallel windings were connected at the same time.
When the first winding is connected, the initial immediately increases to some value and then decreases somewhat. When the second winding is connected, the total current immediately increases, and then ultimately decreases to the normal operating current value. I suspect that the 97 and 158 amp markings represent initial starting current values for the connection of the first winding and the addition of the second. If that is true, the initial current for connecting both winding simultaneously would be significantly higher than 158 amps.
It seems to me that the symbolism makes more sense as Y designates one Y connection winding and YY designates two Y connected windings connected in parallel with each other. Then Y/YY would mean one Y - time delay - YY or part winding start. For a motor with two Y windings direct on line start would be YY.
Unless the manufacturer describes in in more detail or their is a detailed description in a published standard, we can not know for certain what the nameplate means. Even then, there is the possibility that standards have not been followed.