🔍 Key Concepts
• Trace the power path from the supply (L1, L2, L3) through Q1, the contactor (KM1), and into the motor windings (U, V, W).
• Distinguish overload protection (protecting the motor from running above rated current) from short‑circuit protection (protecting wiring from faults).
• Note which devices (OL, FU1–FU3, FU4–FU7) are in the motor power circuit vs only in the control circuit.
đź’ Think About
• Looking at the diagram, which component actually senses the motor’s running current and will trip if the motor is mechanically overloaded but not shorted?
• Which fuses are sized mainly to clear high‑fault currents in the wiring, and which device is designed to respond to a sustained overcurrent just above the motor full‑load current?
• Do the secondary control‑circuit fuses ever see full motor current, or only the small control current for the contactor coil and pushbuttons?
âś… Before You Answer
• Verify which symbol is connected in series with the motor line conductors feeding terminals U, V, and W.
• Confirm which protective device is current‑sensing and thermal (responds to heat from overload), versus devices that are just overcurrent fuses.
• Make sure the device you choose is intended to protect the motor branch circuit and motor, not just the low‑current control wiring.