Motor PLC control ladder diagram

． SB1 is the start button of Ml, and SBZ is the stop button. In the coil control loop of KMOI, the normally closed contacts
of KM02, KMON and KM1 are connected in series to ensure from the hardware that M1 cannot start when other motors are started. The normally closed contact of Lujiezvn can ensure that the motor will not enter the starting state due to misoperation during operation. The start indicator light HL1 and the work indicator light r-h_2 are connected in parallel with the corresponding main contactor coil, which can save the number of output points. The contactor KMO that controls the autotransformer is controlled by KM01 and KM02.     <4) The PI.C control ladder diagram design takes an autotransformer to control the starting of two motors as an example. Just take N-2 in Figure 26-43. The input and output definitions of the PLC are shown in Table 2.6-13.     According to the control requirements and the I/O definition of the PLC, the designed ladder diagram is shown in Figure 26-44.     Take the starting of motor No. 1 as an example. The PLC control process is as follows:     1) When SB11 is connected, Xoo is connected. Y30 action causes KM01 to close. KM01 action causes KMO to absorb. Motor No. 1 is started by decompressing the autotransformer in series .     2) At the same time, due to the function of Ml00, Y30 is self-maintained and T50 starts timing. After a given starting time, the normally open contact of T50 is closed, and Ml01 is energized and self-locked.     3) T50 normally closed contact acts, disconnecting the Y30 and Ml00 coil circuits, causing KM01 and KMO to trip out of power, the autotransformer stops working, the motor starts and is put into full voltage operation.     4) When stopping, press SB12, the xol normally closed contact disconnects the Y31 coil, cutting off power to the Y30 and Ml00 coils, and Y31 acts, causing KM1 to close , thereby causing KMOI and KM02 to trip out of power.     The M102 normally closed contact in the Y30 coil circuit, and the M100 normally closed contact in the Y32 coil circuit prevent the two motors from starting at the same time from the software , and improve the reliability and fault tolerance of the control system.     (5) Conclusion In this example, based on the fact that multiple devices can start at different times in practical applications, PLC and an autotransformer are used to control the starting and operation of multiple large asynchronous motors. In order to ensure the reliability of the system and the safety of equipment operation, the flexibility of PLC control is fully utilized in the design. Safety interlock control is implemented from both hardware and software aspects, achieving satisfactory control effects. Practice has proved that this control scheme is feasible. System costs are significantly reduced and can operate reliably and safely.