The forward reverse motor controlis used i a system where forward and backward or upward and downward movement in the operation are needed.
An example of which are shown in figures below (a) and (b). Figure below (a) shows forward and backward lateral movement of an overhead crane driven by motor M. Figure below (b) shows a downward and upward movement of a load is driven by motor lifter M.
(a) Lateral movement of an overhead crane driven by a motor.
(b) Vertical movement of a lift by a motor.
Control Operation
The clockwise (forward) and counterclockwise (reverse) rotation of a motor can be caused by interchanging the connection of any of the two of its three terminals. Figures (c) and (d) below will show how this can be done.
Contractors F and R are interlocked. It means that if the contacts (1-2, 3-4, 5-6) of contractor R can not be closed. On the other hand if the contacts (1-2, 3-4, 5-6) of contractor R are closed, contacts (1-2, 3-4, 5-6) of contractor F can not be closed.
Note that when the contacts of contractor F in Figure (a) are closed, L1 is connected to T1 through contact F (1-2), L2 is connected to T2 through contact F(3-4), and L3 is connected to T3 through contact R(5-6).The motor M will run forward.
When the contacts of contractor R in the Figure (a) are closed, L1 is connected to T3 through contact R (1-2), L2 is connected to T2 through contact R(3-4) and L3 is connected to T1 through contact R(5-6). The motor M will run reverse.
Referring to the control circuit on Figure (a), pressing the forward push button F will energize contactor F. Maintaining contact F (13 14) will close to maintain contact or F continually energized even if the forward push button is release. Contactor F (11-12) will open to prevent contactor R to be energized. Contacts F(1-2, 3-4, 5-6) will close to run motor M on forward direction.
Pressing the stop push button will de-energized contactor F. This will cause the contacts R(1-2, 3-4, 5-6) to open and stops the motor M from running forward. Contacts F(11-12) will close again. Maintaining contact F(13-14) will open.
Pressing the reverse push button R will energize contactor R. Maintaining contact R(13-14) will close to maintain contactor R continually energize evenif the reverse push R button is release. Contacts R(11-12) will open to prevent contactor F to be energized. Contacts R (1-2, 3-4, 5-6) will close to run motor M on reverse direction.
Pressing the stop push button again will de-energized contactor R. This will cause the contacts R(1-2, 3-4, 5-6) to open and stops the motor from running reverse. Contact R(11-12) will close again. Maintaining contact R(13-14) will open. This brings the condition of the circuit the same as the one shown in Figures (a) and (b) below.
(a) Control circuit of Forward – Reverse Motor Control with limit switches X and Y.
(b) Power circuit of Forward Reverse.
 |
| Add caption |
(c) Connection of Motor to power lines at forward condition.
(d) Connection of Motor to power lines at reverse condition.
Comments
Post a Comment