The solenoid has two windings:
An intermittent-service pulling winding involved in the
initial phase for approximately 150 ms, with the function
of moving the plunger.
A continuous-service holding winding, with the function of
maintaining the plunger in position.
For a proper operation of the solenoid, it is indispensable
for the plunger to reach end of travel and to obtain the
perfect adherence to the bottom.