I. C650 Lathe Control Component Configuration
Figure 1 shows the main electrical control circuit of the C650 lathe.
Figure 1 shows the main circuit of the C650 lathe, which is equipped with three motors M1, M2, and M3. The main motor M1 is controlled by the stop button SB, jog button SB1, forward button SB2, reverse button SB3, normally open contact of thermal relay FR1, forward contact of speed relay KS1, reverse contact of speed relay KS2, main contact of forward contactor KM1, main contact of reverse contactor KM2, and main contact of brake contactor KM3.
The cooling pump motor M2 is controlled by the stop button SB4, the start button SB5, the normally open contact of the thermal relay FR1, and the main contact of the contactor KM4; the fast-traverse motor M3 is controlled by the limit switch SQ and the main contact of the contactor KM5; and the ammeter A is controlled by the intermediate relay contact KA.
II. Main motor forward and reverse rotation control
1. Forward rotation control
Pressing the main motor forward rotation button SB2 closes branch X2. Since X3 and M102 are not activated, M101 is energized and self-locked via branch M101 in branch 7. This results in the following three outcomes:
① When branch M101 of the 8th circuit is closed, timer T1 starts for 0.5 seconds;
② The normally closed contact of the auxiliary circuit M101 in the 12th branch opens, de-energizing the reverse start auxiliary relay M102, thus achieving interlocking between forward and reverse rotation.
③ When M101 in the 17th branch is closed, Y2 is energized, KM3 in the main circuit is energized, causing the series resistor R to be short-circuited.
When branch T1 arrives after a 0.5s delay, branch T1 closes. Since branch Y1 is closed, branch Y0 is energized. Then branch Y0 opens, and the main contact KM1 in the main circuit closes. Motor M1 starts running in the forward direction.
2. The delay effect of T1
The 0.5S delay of T1 ensures that KM3 in the main circuit is energized first, shorting the series resistor R, and then M1 is activated to control the forward rotation of the main contact KM1. Otherwise, the commands to activate contactors KM1 and KM3 are issued from the PLC control software almost simultaneously, which may result in KM1 activating first and KM3 activating later, and the series resistor R not being shorted first.
After the motor M1 starts, the speed increases. When the speed reaches 100 r/min, the forward contact KS1 of the speed relay closes, and X11 of the 22nd branch closes, which is in preparation for the forward and reverse braking action.
3. Reverse control and T2 delay
Pressing SB3 will cause motor M1 to start running in reverse. The 0.5-second delay of T2 ensures that KM3 in the main circuit is energized first, shorting the series resistor R, and then connecting the reverse main contact KM2 of M1.
III. Main motor inching control
Pressing the forward jog button SB1 closes X1 in both the 2nd and 5th branches. X1 in the 2nd branch energizes M103 in the 1st branch, and M103 in the 3rd branch self-locks. At the same time, M103 in the 22nd branch also closes, preparing for energizing T3.
Once the lathe is powered on, M110 of the 5th branch immediately closes. At this time, because X1 in this branch is closed, M100 is energized, causing M100 of the 10th branch to close, Y0 of the 9th branch to be energized, and the normally closed auxiliary contact Y0 of the 22nd branch to open.
In the main electrical control circuit of the lathe, when branch Y0 (9th line) is energized, the main contactor KM1 of the contactor is energized, and the main motor M1 starts and accelerates in the forward direction. After the speed exceeds 100 r/min, the forward contact KS1 of the speed relay remains closed. At the same time, X11 of branch X22 closes, preparing for the reverse braking action.
IV. Inching Stop and Reverse Braking
1. M1 power failure and speed reduction
Releasing the forward jog button SB1 disconnects X1 in both branches 2 and 5, de-energizes M100 in branch 5, and subsequently disconnects M100 in branch 10. This de-energizes Y0 in branch 9 and closes the Y0 contact in branch 22. Consequently, the main contact KM1 in the main circuit opens, de-energizing the main motor M1 and causing it to slow down.
2. M1 reverse braking
Since the speed relay contact KS1 is in the closed state during the initial deceleration, X11 in the 22nd branch is closed. In addition, the Y0 contact in this branch is closed, so T3 is energized and the delay begins.
After the delay of T3, the T3 contact of the 16th branch closes, which energizes the Y1 of the 15th branch. The main contact KM2 in the main circuit is attracted, and the main motor M1 is reverse-connected for braking.
3. Reverse braking ends
When the speed drops below 100 r/min, the forward contact KS1 of the speed relay opens, X11 of the 22nd branch opens, de-energizing T3. The T3 contact of the 16th branch opens, and Y1 of the 15th branch is de-energized accordingly.
When the main contact of KM3 in the main circuit is disconnected, the reverse braking ends, and the main motor M1 stops.
4. The delay effect of T3
The purpose of the 0.5-second delay of T3 is to ensure that KM1 is disconnected before KM2 is connected; otherwise, KM2 will be connected before KM1 is disconnected, which will cause the winding of the main motor M1 to burn out.
V. Main motor reverse braking
1. Main motor power off
When the stop button SB is pressed, the 4th branch X0 is disconnected, M110 is de-energized, causing the normally open contact M110 of the 5th branch to open, and the main control circuit between MC and MCR is no longer executed. As a result, the 9th branch Y0 is de-energized.
When KM1 in the main circuit is disconnected, the main motor M1 is de-energized and slows down. However, as long as the speed of the main motor M1 is greater than 100 r/min, the forward contact KS1 of the speed relay remains closed, and M103 in the first branch is energized due to self-locking.
Pressing the stop button SB will cause the normally closed auxiliary contact X0 of the 9th branch to open, de-energize Y0, and open the main contact KM1 controlled by Y0 in the main electrical control circuit.
2. Enter reverse braking state
Releasing the stop button SB switches SB from the pressed state to the unpressed state, then the 4th branch X0 is closed again, M110 is energized, and the 5th branch M110 is closed, connecting and executing the main control circuit between MC and MCR.
The normally closed auxiliary contact X0 in the first branch also returns to closed, so M103 is energized. At this time, M103 in the 22nd branch remains closed. Since the main motor M1 rotates at a speed greater than 100 r/min, KS1 is in the closed state, and X11 in the 22nd branch remains closed, causing T3 to be energized and the timing to start.
When the timer T3 expires, T3 on the 16th branch closes, energizing Y1 on the 15th branch. KM2 in the main circuit closes, and motor M1 enters reverse braking mode, causing the main motor M1 to decelerate rapidly.
3. The role of T3 delay
The 0.5-second delay of T3 is reflected in the main electrical control circuit. The main contact of KM1 opens first, and the main contact of KM2 closes 0.5 seconds later, which prevents KM1 and KM2 from being connected at the same time and helps to avoid burning out the motor windings.
4. M1 stopped
When the main motor M1 slows down to below 100 r/min, the forward contact KS1 of the speed relay opens, causing X11 of branch 22 to open, T3 to lose power, which in turn causes T3 of branch 16 to open, Y1 to lose power, KM2 in the main circuit to open, reverse braking to end, and the main motor M1 to stop.
5. Reverse braking to stop.
If SB3 is pressed during startup, the main contacts KM3 and KM2 in the main circuit will connect sequentially with a 0.5-second interval, and the motor M1 will start running in reverse. Afterwards, releasing the stop button SB will initiate the reverse braking process.
VI. Monitoring of Main Circuit Operating Current
During the forward and reverse starting process of the main motor, since one of the auxiliary relays M101 and M102 must be energized, T5 in branch 19 is energized, and the 10-second timer begins. After the timer expires, T5 in branch 21 closes, causing Y5 to be energized. The normally closed contact KT in the main circuit opens, and the AC ammeter A monitors the operating current, thus preventing A from encountering a large starting operating current.
VII. Cooling and Fast Motor Control
Both the cooling pump motor M2 and the rapid traverse motor M3 operate in one direction, making control relatively simple. When the cooling pump motor start button SB5 is pressed, X5 of the 25th branch closes, Y3 is energized and self-locked, and the cooling pump motor M2 starts; when the stop button SB4 is pressed, X4 of the 25th branch opens, Y3 is de-energized, and the cooling pump motor M2 stops.
Pressing the limit switch SQ closes X6 of the 27th branch, energizes Y4, and starts the fast traverse motor M3; releasing the limit switch SQ de-energizes the fast traverse motor M3 and stops it.
