Runnable simulator field guide
Two-speed motor PLC scenario: test checklist
Direct answer
The learner can prove stop priority, prevent overlapping speed outputs, transition through the declared stopped state and diagnose failed feedback.
Written for pLC and motor-control learners sequencing low and high speed with mutually exclusive commands and independent running evidence.
Scenario setup
Motor and load, low and high requests, mode, stop priority, permissives, speed contactors or drive command, transition delay, feedback and overload state.
I/O and state map
Operator request through selection, interlocks and final output owner to starter or drive, motor speed and independent feedback.
Normal run
Each speed runs separately, Stop removes both commands and a speed change follows the declared transition without overlap.
Boundary run
Both requests, high selected from standstill, change while running, welded contact, failed feedback, overload, held start, power loss and restart.
Injected fault
A request, priority, selection, state, interlock, output, starter, drive, motor or feedback mismatch.
Target check
The logic validated with the exact motor, switching arrangement, protection and manufacturer transition rules.
Can low-speed and high-speed contactors energize together?
Not unless the exact equipment is specifically designed for that state; typical two-speed control requires electrical, mechanical and software prevention of invalid overlap.
How should a PLC change motor speed?
Follow the approved motor or drive method, often removing the current command, proving the required transition state and then enabling the new speed after a bounded delay.