SeniorStar-Delta sequence~25 min

Star-Delta Motor Starter

The real-world finale: a star-delta starter. Start in STAR to limit inrush, run a 2 s transition timer, switch to DELTA with the two contactors electrically interlocked so they can never be on together. Every element you've learned, in one machine.

Your goal

  • Start (with Stop, sealed) energises Main and Star together.
  • After 2 s, Star drops out and Delta takes over in the same scan, cleanly.
  • Star and Delta must NEVER be on at the same time (interlock each with the other's NC contact).
  • Stop drops everything.
Stuck? Show hints (4)
  1. Rung 1 is your Start/Stop seal on Main: (NO Start OR NO Main) AND NC Stop → OTE Main.
  2. Rung 2: NO Main → TON Ts. The transition clock only runs while the motor circuit is live.
  3. Rung 3: NO Main AND NC Ts.DN AND NC Delta → OTE Star. Rung 4: NO Main AND NO Ts.DN AND NC Star → OTE Delta.
  4. Rung order does the clean handover: at the DN scan, rung 3 drops Star FIRST, so rung 4's NC Star is already satisfied Delta picks up the same scan.

The most-wired motor starter on Earth. Congratulations this is real controls work.

I/O for this exercise

Inputs
StartStart push button
StopStop push button
Outputs
MainMain contactor
StarStar contactor
DeltaDelta contactor
Timers
Ts · 2000msStar-to-delta transition
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