Operation Of The Hydro 124D; The Control Valve Coils - Etesia HYDRO 124D Technical Training Manual

The control valve coils

A coil is a wound up electric cable. A conductor (cable) with an electric current running through
it creates a magnetic field. The winding up of a cable allows a stronger magnetic field to be
obtained and a magnetisable body to be attracted. It is thanks to this effect that we can move a
control valve slide. Thus, a three-position control valve will require two coils : one to force the
slide up, the other to force the slide down. When no coil is live, the slide comes back to its
resting (or neutral) position by the action of springs. In the same way, a two-position slide will
only require one coil, the resting position being obtained with a spring.

OPERATION OF THE HYDRO 124D.

Although the most of the functions are driven by the hydraulics by, the control valves are
controlled electrically. Thus, virtually all the functions send or receive electrical information or
orders. In principle complex, a study of the normal operation of the machine gives information
on the role played by each electrical component. It is therefore essential to know how the
machine operates :
What conditions must be fulfilled to obtain such a function ?
What does this function control ? When ?
What information must this component send ? Where ?
are more or less the first questions that you need to ask yourself before beginning to search
for the origin of a malfunction.
-
59 -