Motor start/stop with overload

What you will build

Work order RE-2601. Riverside Effluent Works, Transfer pump P-101.

Riverside Effluent Works (water treatment) needs a controller program for Transfer pump P-101. Write the start/stop control for a single motor: a seal-in, fail-safe stop and emergency stop inputs, an overload trip and two indicator lamps.

We are replacing the old relay panel for the effluent transfer pump with a PLC, and the motor control comes first. The motor has one contactor, Motor. Start_PB is a momentary push button. Stop_PB and the emergency stop EStop are wired normally closed, so they read 1 when healthy and 0 when pressed or if a wire breaks. The overload relay gives us a normally closed auxiliary contact on OL_Trip: 1 is healthy, 0 means it has tripped. Pressing Start must run the motor, and it must keep running after Start is released. Run_Lamp is on whenever the motor runs. Stop, the emergency stop or an overload trip must stop the motor straight away. After any stop the motor stays stopped until somebody presses Start again: it must never restart by itself when a stop button is released or the overload is reset. Start must do nothing while Stop, the emergency stop or the overload is active. Fault_Lamp is on while the overload is tripped.

What you will learn

• Seal-in circuits
• Normally closed safety inputs
• Fail-safe stop logic
• Indicator lamps
• Read a short user requirement specification (URS) and turn it into ladder logic
• Prove your program against a numbered factory acceptance test (FAT)

How it goes

1. Read the work order and the URS.
2. Build the ladder program against the tag table.
3. Run the plant and watch it respond.
4. Run the FAT and fix whatever fails.

Tools

• Ladder editor in the browser

  Draw contacts, coils, timers and counters, then run the program.

• A working simulated plant

  Watch the machine respond as your logic runs.

• A tag table

  4 inputs and 3 outputs: Start_PB, Stop_PB, EStop, OL_Trip, Motor, Run_Lamp, Fault_Lamp.

• URS and FAT documents

  The paperwork a real project starts from, with numbered tests.

Questions

Is it free?

Yes. The lab is free to use with a free account. There is nothing to buy to open this scenario.

Do I need to install anything?

No. It runs in your browser with the ladder editor and a simulated plant.

What will I do in PLC-01 Motor start/stop with overload?

You build and test a program, then check your work against an acceptance test.

How long does it take?

A first attempt takes about 45 minutes.

Do I need experience?

No. Each work order says what to do step by step, and hints are there if you get stuck.