Q5Electrical Machines and Drives

A capacitor-start induction motor creates a strong, near-90-degree phase-displaced starting winding current using a capacitor in series with the auxiliary winding, producing a starting torque that can reach 3-4.5 times full-load torque. A repulsion motor's starting torque, though also high, depends on brush-gear positioning and commutator condition, making it mechanically more complex and less reliable to maintain; the capacitor-start motor achieves comparably high starting torque with a simpler, brushless, more rugged and lower-maintenance construction, which is why it is preferred wherever high starting torque is needed without the complexity of brushes and commutator.