🔍 Key Concepts

• Synchronous speed formula for AC motors: how speed depends on frequency and number of poles • Difference between synchronous motors and induction motors in terms of running speed and slip • Effect of number of poles (4-pole vs 6-pole) on motor RPM at the same frequency

💭 Think About

• First, decide which has the higher theoretical synchronous speed: a 4-pole motor or a 6-pole motor at the same frequency. Why? • Next, think about the difference between synchronous and induction motors: which one actually runs exactly at synchronous speed, and which one runs slightly below it? • How does load (no load vs normal load vs full load) affect the slip of an induction motor, and therefore its actual RPM compared to synchronous speed?

✅ Before You Answer

• Write down and compare the synchronous speeds for 4-pole and 6-pole motors at the same frequency before looking at the options. • Recall that a synchronous motor has essentially zero slip in normal operation, while an induction motor must have some slip to produce torque. • Check which option combines the fewest poles and least effect of slip to give the highest actual RPM.