Applying the brake as the frequency passes through zero
In Open-loop mode the torque produced may reduce as the frequency passes through zero. To prevent the load from falling during this period in a vertical application, it is possible to apply the brake
momentarily to hold the load. If BCBrakeApplyThroughZeroThreshold (12.051) = 0 then the brake is not applied when the frequency passes through zero unless ReferenceOn (01.011) = 0.
If BCBrakeApplyThroughZeroThreshold (12.051) is non-zero then the brake is always applied when the modulus of frequency is less than BCBrakeApplyThroughZeroThreshold (12.051) even
if ReferenceOn (01.011) = 1. This ensures that the brake is applied and then released as the frequency passes through zero. BCBrakeApplyThroughZeroThreshold (12.051) should be set to a
value that is lower than both BCBrakeReleaseFrequency (12.044) and BCBrakeApplyFrequency (12.045) so that it does not interfere with the control of the brake when starting and stopping.
Forced initial direction
If BCInitialDirection (12.050) = 0 then the brake controller operates as described above and the user reference is used to define the direction of operation. If BCInitialDirection (12.050) = 1 then
ForceReferenceDirection (01.057) is used force the frequency reference to the positive modulus of the selected user reference until the end of the post-brake release period whatever the direction
of the user reference. This can be used for example to ensure that in a vertical application the motor will definitely hold the load at the point when the brake is released. The diagram below shows the
brake controller sequence when BCInitialDirection (12.050) = 1, but the user reference direction is reverse. It should be noted that BCInitialDirection (12.050) has no effect if
BCBrakeApplyThroughZeroThreshold (12.051) is non-zero, and the user reference direction is always used as the initial direction, to prevent a condition where the brake would release then apply
repeatedly.
If BCInitialDirection (12.050) = 2 then ForceReferenceDirection (01.057) is used to force the frequency reference to minus the modulus of the user selected reference until the end of the post-brake
release period to ensure that the output frequency is negative during this period.
Parameter 12.041 BC Enable
Short description Enables the brake control function
Mode Open‑loop
Minimum 0 Maximum 3
Default 0 Units
Type 8 Bit User Save Update Rate Action on exit from edit and reset
Display Format Standard Decimal Places 0
Coding RW, TE
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