1. Control requirements

There are three motors in a control system. When the start button SB1 is pressed, the lubrication motor starts; After running for 10s, the main motor starts; After running for 20s, the motor of cooling pump starts. When the stop button SB2 is pressed, the main motor stops immediately; After the main motor stops for 5 seconds, the cooling pump motor stops; After the cooling pump motor stops for 5 seconds, the lubrication motor stops. When any motor is overloaded, all three motors stop.

2. I / O allocation

Input signal: start sb1-x0;

Stop sb2-x1;

Overload protection of the first motor – X2 (connected to normally closed contact);

Overload protection of the second motor – X3 (connected to normally closed contact);

Overload protection of the third motor – X4 (connected to normally closed contact).

Output signal: Lubricating motor – Y0;

Main motor – Y1;

Cooling pump motor – Y2.

3. Program design

The PLC control system is a typical sequence start, reverse sequence stop control. The procedure is shown in the figure below.

How to control motor sequence start by PLC

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