Several crane lifting mechanism protection device

One, zero and voltage protection circuit:
      Electric  hoist gantry crane  upgrade, Zhang closing cam controller zero contact with the four motor overcurrent relays normally closed contacts in series with the relay coil loop at zero pressure, only in upgrading, Zhang closed master controller handles are at zero, the zero pressure to energize the relay coil and through one pair of normally open contacts remain self-locking.
2, to enhance, Zhang closed loop interlocking protection:
       In upgrading and Zhang closing contactor coil circuit, each string and then in the opposite direction contactor normally closed contact, which decreased lift circuit in series with the contactor normally closed contact, a decrease in series with the contactor coil circuit increased contacts normally closed contact, the same, electric hoist gantry crane Zhang bucket bucket and closed contactor coil circuit also string then the other normally closed contact. This prevents misuse under fault conditions or when there is a power short circuit may.
3, enhance, Zhang closed loop limit, overweight protection:
       Electric hoist  overhead gantry crane  rise and fight off the contactor coil circuit, the common string into the upgrade limit, fighting off limit and load cell normally closed contact. When grab upgrade to a predetermined position, the limit switch is open, cut off the power grab lift circuit, protective equipment safety; grab grab when the material exceeds the limits of the  bridge gantry crane   overweight sensor sends an alarm and cut grab promotion loop power supply in order to prevent accidents.
4, enhance, Zhang closed brake circuit:
       Electric hoist gantry crane upgrade, Zhang closed brake (hydraulic pusher) There are four, respectively, by two contactor control. When upgrading, Zhang closed contactor is switched on, which they followed a pair of normally open contacts close and turn the corresponding brake contactor coil circuit, the power brake motor running, brake open, improve Zhang progressively closed motor revving.