Which of the following statements is true concerning the manual motor starter diagram shown in figure "A" of the illustration? See illustration EL-0023.
• Trace each phase from L1, L2, L3 to T1, T2, T3 and count how many lines pass through an OL (overload) device. • Recall the difference between thermal overload protection (heaters/bimetal elements for running overload) and magnetic protection (instantaneous trip for short-circuit). • Note that a manual motor starter typically combines a switch with overload protection – the symbol "OL" is important.
• Looking at figure A only, how many motor leads actually pass through devices labeled OL before going to the motor terminals? • Does the symbol used for OL look like a heater/bimetal (thermal) element in series with the line, or like a magnetic trip coil associated with a circuit breaker? • Is there any indication that only two lines are monitored for overload while one line bypasses the overload devices? Or are all three lines treated the same?
• Count carefully whether all three motor leads (T1, T2, T3) route through overload elements, or only two of them. • Confirm that the OL devices are in series with the motor lines, indicating thermal overload heaters rather than a separate magnetic trip unit. • Verify that no line to the motor bypasses overload protection; this will determine whether it is two-leg or three-leg protection.
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