Learning outcomes
- Explain the key principles of direct-on-line, star-delta and reversing starters.
- Carry out a structured practical check or configuration task.
- Recognise common faults, risks and evidence needed for diagnosis.
Module 3 · Lesson 2
Direct-on-line, star-delta and reversing starters
Commission and diagnose common motor starter configurations and their interlocks.
Before you begin
Approved starter drawings and isolated motor circuit.
Safety: Use site procedures, approved test equipment and competent supervision. Never bypass a protection or interlock without formal control.
Step-by-step learning
- Confirm phase sequence and motor connection before energising.
- Verify overload setting from nameplate current and site requirements.
- Test stop, emergency stop, overload and process interlocks.
- Run briefly, check rotation, current balance, noise and acceleration.
Ian's practical tips:
- Reverse two phases only after safe isolation when correcting rotation.
- Star-delta transition problems often come from timer settings, wiring or mechanical load.
Fault-finding questions
- What should be happening, and what evidence proves it?
- Where is the last known correct signal, voltage, state or process condition?
- What changed immediately before the fault?
- Can the system be divided into smaller testable sections?
Practical activity
Create a one-page test record for this lesson. Include expected values, measured results, equipment used, risks controlled, defects found and the final proven condition.