š Key Concepts
ā¢ Identify which devices are in the power circuit (feeding the motor directly) versus which are in the control circuit (feeding the contactor coils KM1, KM2, KM3).
ā¢ Trace the control-circuit path from the transformer secondary (X1āX2) through the fuses, switches, and relay/contactor coils to see what actually loses power if a short occurs.
ā¢ Understand the specific job of overload relays (OL) versus fuses (FU) in protecting against overcurrent and short-circuit faults in the control circuit.
š Think About
ā¢ On the right-hand side of the drawing, follow the control-circuit from X1 and X2: which protective components are the first to āseeā a short-circuit in that low-voltage wiring?
ā¢ If those protective devices open, what happens to the coils of KM1, KM2, and KM3, and therefore to the motor on the left side?
ā¢ Compare which listed choices protect the motor power lines and which protect the low-voltage control wiring; which group directly removes power from the contactor coils during a control-circuit short?
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Before You Answer
ā¢ Verify which fuses (FU1āFU3, FU4āFU7) are on the line side feeding the motor versus the low-voltage control side from the transformer secondary.
ā¢ Check which componentās opening would deāenergize the contactorsā coils (KM1, KM2, KM3) even if the main line fuses FU1āFU3 remain intact.
ā¢ Confirm the normal function of overload relay OL: does it respond to motor current overload in the main circuit, or to short-circuit current in the control circuit wiring?