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The operating mechanisms of circuit breaker contacts are crucial for their functionality, enabling them to open and close in response to electrical faults. Among the options listed, the rotary mechanism is not typically considered a main operating mechanism.

Hydraulic mechanisms utilize fluid pressure to operate the contacts, allowing for a rapid disconnection of the circuit when needed. Pneumatic mechanisms, which rely on air pressure, can also be used for opening and closing the contacts in some circuit breakers. Solenoids, which are electromagnetic devices, convert electrical energy into linear motion, making them effective for shifting contacts in a circuit breaker.

In contrast, the rotary mechanism is not commonly employed as a primary function in circuit breakers. It may refer to a movement type that is not suitable for the quick and reliable operation necessary for interrupting electrical currents. Thus, the absence of the rotary mechanism as a main operating mechanism distinguishes it from hydraulic, pneumatic, and solenoid options that directly fulfill the requirements of circuit interruption.