🔍 Key Concepts

• Electrical interlock using normally-closed (N.C.) auxiliary contacts in the control circuit • How each contactor coil (M1–M6) is wired on its own rung in the lower (control) diagram • Difference between overload contacts (10L, 20L, 30L, 40L) and interlocking contacts from other contactors

💭 Think About

• On the rung that energizes coil M4 (3rd speed), which N.C. contacts must current pass through before it reaches the M4 coil? Note the labels printed beside those contacts. • When any of those other contactors energize, what happens to their N.C. auxiliary contacts in M4’s rung, and how does that prevent M4 from picking up at the same time? • Compare the rungs for 2nd, 3rd, and High speed: which other contactor coils would create a conflicting speed if they were energized with M4, and do you see their N.C. contacts in series with the M4 coil?

✅ Before You Answer

• Be sure you are only counting N.C. auxiliary contacts on the M4 coil rung, not overloads or stop buttons. • Confirm each N.C. symbol’s label: only list the contactors whose names are printed next to those contacts (e.g., M1, M2, M3, M5, M6). • Verify that each contact you pick is truly in series with M4’s coil, so that opening it will de‑energize M4.