Early alternating-current power systems suffered from a major operational limitation: synchronous AC motors could not start on their own. Although such motors could run efficiently once synchronized with an AC generator, they produced no starting torque from rest. Consequently, existing systems relied on mechanical starters or complex auxiliary arrangements, increasing system complexity and reducing reliability.

In his 1889 patent, Nikola Tesla proposed a purely electrical solution to this problem by introducing a method that temporarily alters the circuit configuration during startup, without modifying the motor’s mechanical construction 
Tesla’s system employs both the generator and motor with two coils or sets of coils. During normal operation, these coils form a single-circuit system suitable for synchronous running. However, during startup, Tesla establishes a temporary electrical connection between the intermediate points of the generator and motor circuits—commonly through a ground connection. This converts the system into an effective double-circuit configuration, allowing current paths that produce starting torque.

In this startup mode, the ground serves as a common return path for the two circuits, enabling the motor to accelerate from rest. Once the motor reaches or closely approaches synchronous speed, the temporary connection is interrupted using switches. The system then automatically reverts to a single-circuit synchronous configuration, in which the motor locks into synchronism with the generator and continues stable operation.