🔍 Key Concepts
• Examine how the external resistors (1A, 2A, 3A, 4A) are connected to the motor terminals M1, M2, M3 and what that says about the rotor circuit.
• Compare the control circuit shown to typical starting methods for a squirrel-cage induction motor vs a wound-rotor induction motor.
• Think about whether a synchronous motor or stepper motor would normally have this type of three‑phase contactor and resistor arrangement for hoist speed/torque control.
💭 Think About
• What does the presence of multiple resistor stages, switched in and out by contactors, usually indicate about how starting torque and speed are controlled in an AC hoist motor?
• If the motor were a squirrel‑cage type, where would any starting or speed‑control resistors have to be placed, and do you see that arrangement here?
• Would a synchronous or stepper motor typically be started and controlled only with three‑phase AC lines L1–L2–L3 and rotor resistors, or would you expect some other kind of excitation or control electronics? (Look for that in the drawing.)
✅ Before You Answer
• Trace from terminals M1, M2, M3 through the resistors labeled 1A–4A and confirm whether they form an external rotor circuit.
• Verify whether there is any separate DC supply or electronic pulse control that would be required for a synchronous or stepper motor; note if it is absent in the illustration.
• Confirm that the stator is connected directly to L1, L2, L3 through overloads and contactors, while the resistors are only in series with the other set of motor terminals.