Q: Page 87. Electromechanical Relays, in the list of Application Data there is parameter Ubob, but in the formula for Electrical factor this (Ubob) parameter doesn't exists, instead we can find Uwinding. Is it the same parameter?

"Bob" was an abbreviation from the French "Bobine" and should have been translated in "winding coil". Therefore U_bob is U_winding. No, the ratio U_rated / U_winding is correct. If the command voltage (U_winding) is low, the relay may have problem to operate and this accelerate failure rate.