🔍 Key Concepts

• Three-phase induction motor rotation depends on the phase sequence of the supply to the main (stator) winding. • In a wound-rotor induction motor, the rotor (through M1, M2, M3 and the rheostat) mainly affects starting torque and speed control, not the phase sequence of the rotating field. • Reversing direction in three-phase motors is normally done by changing the order of any two of the three-phase supply lines feeding the main winding.

💭 Think About

• From the illustration, decide which terminals (T1, T2, T3 or M1, M2, M3) are connected directly to the three-phase line labeled L1, L2, L3. • Ask yourself: which winding actually produces the rotating magnetic field that the rotor follows—the stator winding or the rotor winding with the external rheostat? • If you changed the connections on the rotor only, without changing the stator phase sequence, would the direction of the rotating magnetic field in the air gap really reverse?

✅ Before You Answer

• Identify from the diagram which leads go to the circuit breaker and line supply and which go to the rheostat. • Confirm which winding is the stator and which is the wound rotor in this figure. • Before choosing, verify whether reversing both sets of leads would, in effect, undo the reversal you are trying to create.