The intensity set point may be chosen as high as possible,
but not too close to the maximum to avoid transitory
overlapping due to disturbances.
When WC, the master–slave structure of the temperature
control helps the intensity controller operation. If
the intensity rises, the outlet temperature diminishes, as
shows Fig. 10, although this relation is not univocal because
of the effect of several disturbances. Then, the inlet
temperature has to increase trying to maintain the outlet
temperature, the solid loses more water, and so the
intensity brings down.
Fig. 11 shows the behaviour of the WC control system
during a six-hour period. It can be seen that the control
system keeps the intensity within a narrow range.
For comparison, Fig. 12 shows, at the same scale, the
intensity variation under manual control. It is clear that
the fluctuating range is wider than with the automatic
control system and, as can be seen, the intensity even
goes beyond 160 A occasionally