How to Operate a Group of Induction Motors using PLC Logic?

The induction motor is one of the significant elements of any electrical system (production line), as its low costs, operation in a wide range of industrial conditions, and finally, the simple design and rugged construction make them the best in use.

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Induction Motors PLC Logic

But as we discussed in the previous article earlier, there are some problems that occurred with the miss operating a group of Induction Motors.

So, in this lesson, we will discuss how to make a PLC logic that could handle and control a group of induction motors smoothly and without any problems.

Example For “Operation of Three Induction Motors”

Here we will make a PLC program that can handle the operation of three induction motors that is needed to be operated in a specific order.

Once the operator presses the start push button the first induction motor will run and after five seconds the second motor will run finally and after additional five seconds the third motor will take the order to run.

After the three motors are running and once the operator presses the stop push button the three motors will stop (with the same periods between each motor) but with an opposite sequence as shown in Fig. (1).

Operation of Three Induction Motors — Figure 1

Programming of PLC Code

Here we are dealing with SIEMENS PLCs (S7-1200) using the ladder diagram.

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Network 1 – First Motor Start Stop Logic

Once the operator presses the start push button as we can see in Fig. (2), (I0.0) will energize the output coil (Q0.0) that is responsible for turning the first induction motor on.

First Motor Start Stop PLC Code — Figure 2

Network 2 – Second Motor Delay Logic

Then after the first motor is turned on (Q0.0), it will start a delay timer (DB5) with a preset time of 5 Seconds.

Network 3 – Second Motor Start Stop Logic

As we can see In Fig. (3) the output of the delay timer (M0.0) will be responsible for turning the second induction motor on (Q0.1), then the motor will latch on itself and it will resume running.

Network 4 – Third Motor Delay Logic

Then after the second motor is turned on (Q0.1) (NOTE: stop push button is NC) and we did not press the stop push button, the second motor coil (Q0.1) will start a delay timer (DB6) with a preset time of 5 Seconds. As shown in Fig. (4)

Network 5 – Third Motor Start Stop Logic

As we can see In Fig. (4) the output of the delay timer (M0.1) will be responsible for turning the third induction motor on (Q0.2), then the motor will latch on itself and it will resume running.

PLC Induction Motors Start Stop Logic — Figure 4

Once the operator presses the stop push button as we can see in Fig. (4), immediately (I0.1) will de-energize the output coil (Q0.2) that is responsible for turning the third induction motor off.