Control and protection circuit composed of master switch and cam controller

The main circuit composed of the master switch and cam controller is shown in Figure 8-8, and the control and protection circuit is shown in Figure 8-9.
This circuit is mainly used for bridge cranes with two hoisting mechanisms
. The rated lifting capacity of the main hook is 15 (20)t and the rated
lifting capacity of the auxiliary hook is 3 (5)t. The main and auxiliary hooks
are driven by electric motors Ms and M4 respectively, the cart is driven by Mi and M2 respectively, and the small cart
is driven by M3.
    The cart uses a KT14-25J/2 cam controller SAi to simultaneously control the start, speed change, reverse and stop
of the electric motors Mi and M2 .
The cart's left and right movement and limit protection
are controlled by limit switches SQ4 and sQs respectively. The trolley and auxiliary
hook use two KT14-25lJ cam controllers SA2 and
SA3 to control the start, speed change,
reverse and stop of the motors M3 and M4 respectively. The limit protection of the trolley and auxiliary hook
is realized by limit switches s06, SQ7 and sQa.
    The main hook adopts LKl-12/90 type master controller. It
and the PQR10B-150 AC magnetic control panel jointly control
the main hook's rise, fall, braking, speed change and stop. The main hook
lifting limit protection is implemented by the limit switch SQio. The closing conditions of each contact of
    the master controller SAo and cam controller SAi~SA.3 are shown in Table 8-6 to Table 8-9 respectively.
In the table,
“×” indicates closed status.