🔍 Key Concepts

• Three-phase induction motor operation and how torque is produced by a rotating magnetic field • What happens to the rotating magnetic field if one phase (line) is lost • Difference between starting a motor and keeping it running when one phase is missing

💭 Think About

• Think about whether the rotor can still see a rotating magnetic field with only one phase, or if it effectively becomes a single-phase motor with a very weak or pulsating field • Consider whether a motor that was already running on three phases behaves differently from a motor that is trying to start on only one phase • Ask yourself what effect loss of one phase has on torque and heating of the windings

✅ Before You Answer

• Verify what happens to a running three‑phase motor when it suddenly becomes single‑phased (one line opens) • Check whether a three‑phase induction motor can self-start on only one phase • Consider the relationship between load level and the motor’s ability to keep turning when one phase is lost