No-load switching 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 times 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 switching frequency than would be the case with a lower no-load switching 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, the following 3 design requirements must be observed for cycle design:

• The permitted no-load switching frequency Z_B0 of the brake must not be exceeded (formula 1.5). The permitted values depending on size and control method can be found in the section No-load switching frequency.
• The intervals between switching on, switching off, and then switching on again must be such that the brake has time to convert the electrical switching command into a mechanical reaction (application or release). Observe the switching times t₁ and t₂ of the brakes 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. For the minimum pause times, refer to the technical data in the product manual of the brake controls.