Wiring 21 — Forward / Reverse Motor Starter

Forward / Reverse Motor Starter

Wire paired forward and reverse contactors. The forward contactor preserves phase order; the reverse contactor swaps L1 and L3 before the common overload. A common Stop/overload chain and separate relay NC contacts provide electrical protection and cross-interlocking in addition to the mechanical interlock expected between contactors.

Why it is wired this way

Reversing any two phases reverses a three-phase motor. Both contactors must never close together: the power poles would create a phase-to-phase short. Mechanical and electrical interlocks are deliberately redundant.

Commissioning standard

Before energising, prove protective earth and continuity, verify the drawing terminal-by-terminal, then energise through the protective device and measure the expected supply, signal and return values. Never use this training panel as a substitute for the machine manufacturer’s instructions, risk assessment, isolation procedure or applicable electrical standard.