No-load starting frequency for holding brakes

Inverter-operated drives are capable of handling dynamic motion requirements and short travel cycles. For drives with brakes, 3 important limit conditions must be observed in the cycle design:

  • The magnet system of the brake requires time to execute the requested switching command (close or open).
  • The brake control requires time for the involved electronic components to execute their state changes, e.g. charging of capacitors.
  • Brakes that are operated with high-speed excitation, e.g. with BME.. series brake controls, are loaded with a higher mean rms current at a higher no-load starting frequency than would be the case with a lower no-load starting frequency. The reason for this is the higher time proportion of the inrush currents. The result is greater heating and a higher load on the brake coil.

For the above reasons, you must observe the following three design requirements when designing the cycle:

  • The permitted no-load starting frequency ZB0 of the brake must not be exceeded (formula 2.2 and 3.2). For the permitted values depending on size and control method refer to Permitted no-load starting frequency of the brake ZB0.
  • The intervals between switch-on, switch-off and subsequent restart must be designed so that the brake can convert the respective electrical switching command into a mechanical response (application or release). Observe the switching times t1 and t2 of the brakes as specified in chapter Pulse frequencies as well as the response times and signal propagation times of the application.
  • Adhere to the minimum pause times before switching on again, depending on the type of brake control, see Minimum pause times before switching on again.