How do induction motors work, what is slip, and how is a star-delta starter controlled in ladder logic?

flowchart TD
    A[Start PB] --> B[Stop PB NC]
    B --> C[OL NC]
    C --> D[M Main]
    A --> E[S Star]
    E --> F[Timer]
    F --> G[D Delta]
    E -->|NC| G

• Principle: stator 3-phase windings create rotating magnetic field; field induces current in rotor bars; interaction of stator field and rotor current field produces torque
• Slip: rotor runs slightly slower than synchronous speed; slip is this difference
• Star-delta starting: windings start in star, cutting phase voltage and current to about a third, then switch to delta after timer delay
• Ladder logic components: Start PB (NO), Stop PB (NC), OL (NC), Main contactor (M), Star contactor (S), Delta contactor (D), Timer (T), S-NC interlock to D
• Sequence: Start → M & S energize → timer runs → S drops out, D energizes → motor runs in delta
• Requirement: TEAP Part B, Electrical, Electronic & Control Engineering, operational level
• ETO role: select starting method, verify interlocks, troubleshoot control sequence