L68B3 Mast SectionThe cause of the slide hook, a simple circuit to prevent the tower crane from blocking the slide hook
It is very dangerous for the tower crane to slide the hook in the neutral position, especially when it changes from high speed to low speed in the process of lowering. Once there is a slide hook, the light one will smash through the floor to destroy the equipment and the heavy one will hurt the construction personnel. Why do you have a slide hook? In order to solve this contradiction, the tower crane manufacturer (http://www.fx68.net) has designed a simple circuit to prevent the tower crane from sliding hook in the neutral position on the basis of absorbing the advantages of the circuits of major companies.
L68B3 Mast Section：
http://www.towercranesupply.com/product/l68b3-mast-section-for-tower-crane-masts
The reason is that there is a long-time neutral gear in the process of gear switching (such as the long gear gap of linkage platform, the damage of contactor coil, the aging delay of delay head, etc.). In the control circuit of multi speed motor, in order to prevent phase to phase short circuit in the process of shifting, a neutral gear of about 0.1s must be designed, otherwise the breaker will trip or the contactor will burn.
In the control circuit of the brake motor of the hoisting mechanism, the normally open contact of each gear is connected in series. Once the contactor of a certain gear is not closed, the hoisting mechanism will stop working by braking.
You have such a doubt: in the process of each shift, the brake motor will brake once due to a short power shortage. Will it damage the brake motor and lifting mechanism?
L68B3 Mast Section：
http://www.towercranesupply.com/product/l68b3-mast-section-for-tower-crane-masts
In our opinion, as long as the neutral time is within a proper range, it will not cause damage to the brake motor and lifting mechanism. Because the brake mechanism has a braking distance, the brake motor will lock up when the power is cut off for about 0.5 seconds. If the neutral time is controlled below 0.2 seconds, the brake motor will only act once and will not brake. Only when the neutral time exceeds 0.5 seconds, the brake will really work and everyone will worry. In other words, what does it mean to be in neutral for more than 0.5 seconds? That means major security risks! Even if the brake will damage the lifting mechanism at this time, it is also the only choice for the car to lose its guard.
