Does a brake's holding torque prove it can stop the rotor repeatedly?

The short answer

No. Holding torque describes resistance at rest, while stopping requires dynamic friction and absorption of energy over time. A wind-rotor mechanical brake must have documented dynamic torque, event energy and repeated-duty capability for the intended condition, if such a brake is actually fitted.

Separate restraint from energy dissipation

A stationary holding brake carries torque without continuing rotational work at a stopped interface. During a stop, friction acts through angular displacement and converts mechanical energy into heat. Rotor inertia and ongoing aerodynamic input can both matter. A high holding-torque number therefore does not establish how much energy the brake can absorb or what speed and duration its dynamic rating permits.

Define the complete stopping duty

Record initial speed, relevant inertia, external driving torque, stopping method and repetition/starting temperature. A cold single stop and repeated stops can have different thermal demands even with the same initial speed. Mayr explicitly distinguishes static and dynamic braking torque and friction-pairing influences. Those distinctions do not establish a MARSTON brake type or a universal ratio between its static and moving capacities.

Request a brake-specific selection

Ask the turbine designer which stopping/holding functions the mechanical brake is intended to perform and request the manufacturer’s rating evidence for each. Include disc, caliper, mounting and cooling boundaries where relevant. Do not infer emergency-stopping capacity from a parking or holding label, and do not perform an improvised stopping test. The decision is whether the supplied brake assembly is assessed for the actual dynamic and repeated-energy duty, rather than merely able to resist one stationary torque. If stopping energy is shared between electrical and mechanical paths, identify the credited share and failure cases. A mechanical holding rating cannot establish the energy the brake may receive when the normal electrical path is unavailable.