Hysteresis brakes must be operated below their maximum RPM rating.
The max. RPM is limited by the balance of the rotating parts. For applications requiring higher RPM, please specify brakes with rotating parts that have been selected for lowest runout, which are better balanced.
Usually the slip heat dissipation rating is the governing factor on how fast a brake may run in a certain application, and not MAX RPM. Slip heat formulas determine limits of simultaneous torque and RPM, to prevent overheating.
Other important formulas are on the sizing page.