🔍 Key Concepts
• Autotransformer reduced‑voltage starter layout in the power circuit (bottom half of the diagram)
• Functions of the three power contactors: 1S, 2S, and R during start and run
• Difference between connections on the line side (L1–L3) and the motor side (T1–T3)
đź’ Think About
• During the starting/acceleration period (before the run contactor R closes), trace the path from L1, L2, and L3 to the motor terminals T1, T2, and T3. Through which device do the currents pass just before entering the motor?
• Look closely at the symbols and labels on the autotransformer windings: does this diagram actually show any delta or wye connection, or is it simply tapped windings? How does that affect which answer choices can be eliminated?
• Compare what changes in the circuit when R eventually energizes: which contactor is now bypassing the autotransformer, and which contactor was responsible for involving the autotransformer during the start period?
âś… Before You Answer
• Identify exactly where the 1S main contacts are located in the power circuit and what two parts of the circuit they bridge (for example, between a tap and the motor, or between the line and the transformer).
• Verify which contactor’s main contacts are directly in series with the incoming lines L1–L3 and the transformer windings; that contactor is the one that actually connects the transformer to the line.
• Confirm that the question specifies the starting/acceleration period, not the run period, and match that to which contactors are energized in that phase of operation.