Limiting the Forward and Reverse Motion of an overhead crane driven by a motor

The motion of an overhead crane moving forward and reverse can be automatically stop at both end by placing a limit switches X and Y in the control circuit of the Forward – Reverse Motor Control shown in Figure below (d).

Refer to Figure below (d). When contractor F is energized, the motor runs clockwise. The motor drives the overhead crane to move the right (forward) direction as shown in Forward Reverse Motor Control . Before the crane could reach the right end wall, it will hit the Limit switch X. Limit switch X will open its normally closed contact X(1-2) to de-energized contactor F. With contractor F de-energized. The overhead crane will stop and it will never have a chance to hit the right end wall. Pressing the forward push button will never make the motor run and the overhead crane remains immobilized.

However, pressing the reversed push button will energized contractor R and will enable the motor to run in counterclockwise direction. The motor will drive the overhead crane to move to the left (reverse) direction. Before the crane could reach the left end wall, it will hit the limit switch Y. Limit switch Y will open its normally closed contact (1-2) and de-energized contactor R. With contractor R de-energized, the overhead crane will stop and prevented from hitting the wall at the left end. Pressing the reverse push button will never make the motor run and will render the overhead crane immobilized.

                The motion of an overhead crane shown in Figure above (d) can be automatically change to opposite direction when it reaches both end, that is hitting the limit switch X and Y without pressing the forward and reverse push button switches any longer. This can be done by connecting terminal 3 of limit switch X to terminal 11 of contact F(11-12). And connecting the terminal 3 of limit switch Y to terminal 11 of contact R(11-12), see Next Article: Automatic Forward and Reverse Motion