Brake closing threshold

In some cases, a low speed does not make any sense from the application point of view. This includes applications with unfavorable load features, such as static friction. In such applications and depending on the type of control, a low speed may cause an unwanted behaviour. In order to prevent such an operating situation, a closing threshold can be set. The power section will only be switched on and the holding brake is opened if the setpoint is higher than the closing threshold. In order to prevent the holding brake from being closed if the setpoint only shortly falls below the closing threshold during operation, a delay time can be set in addition.

Preconditions

If the holding brake is controlled manually via an external control signal: It must be ensured that the motor does not move while the motor control is deactivated by this function.

Details

The function is part of the holding brake control and does not have independent functionality.

Relevant parameters:

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0x2820:007 (P712.07): Brake closing threshold

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0x2820:012 (P712.12): Closing threshold delay

Setting notes:

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The function is active if the brake closing threshold is higher than 0 Hz.

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In order that the brake can work correctly, the brake closing threshold must be set to a value that is greater than or equals the minimum frequency 0x2915 (P210.00).

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The brake closing threshold has a permanent hysteresis of 1 Hz in order to prevent an unwanted change-over. Exception: If the brake closing threshold is set to 0 Hz, the hysteresis is also 0 Hz.

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If the brake closing threshold is set to 0 Hz, a start command is only required to release the holding brake during automatic operation.

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This function can be combined with the setting of a holding load.

Parameter

Address	Name / setting range / [default setting]	Information
0x2820:007 (P712.07)	Holding brake control: Brake closing threshold (Brake control: Closing thresh.) 0.0 ... [0.2] ... 599.0 Hz	Threshold for closing the holding brake. – The power section will only be switched on and the holding brake will be opened if the setpoint is higher than the threshold set here. – In order that the brake can work correctly, the brake closing threshold must be set to a value that is greater than or equals the minimum frequency 0x2915 (P210.00). – The brake closing threshold has a permanent hysteresis of 1 Hz in order to prevent an unwanted change-over. Exception: If the brake closing threshold is set to 0 Hz, the hysteresis is also 0 Hz. – In case of a setting of "0 Hz", only a start command is required to release the holding break during automatic operation.
0x2820:012 (P712.12)	Holding brake control: Closing threshold delay (Brake control: ClosingThr delay) 0 ... [0] ... 10000 ms – From version 03.00	By setting a deceleration, a closing of the holding brake can be prevented if the frequency only temporarily falls below the brake closing threshold 0x2820:007 (P712.07).

General mode of operation

The following diagram demonstrates the general functioning in automatic operation:



①	If the inverter is enabled and no error is active, the motor can be started with the "Run" function in forward rotating direction. The power section is switched on and the motor is magnetized first.
②	The holding brake is released. In this case, the output trigger "Release holding brake [115]" is set to TRUE. This trigger must be assigned to a digital output or, in the simplest case, to the relay which then switches the brake supply.
③	After the release time 0x2820:003 (P712.03) has elapsed, the motor is accelerated to the setpoint. In 0x2820:015 (P712.15), the brake status "Brake released [1]" is displayed.
④	If the direction of rotation reverses, the holding brake remains released (even if the closing threshold delay is running.)
⑤	If the setpoint selection and the internal setpoint for the motor control fall below the brake closing threshold set in 0x2820:007 (P712.07), the output frequency is ramped down to "0 Hz". At the same time the closing threshold delay set in 0x2820:012 (P712.12) starts to run.
⑥	If the values fall below the closing threshold longer than the closing threshold delay, the holding brake is closed again.
⑦	After the closing time 0x2820:002 (P712.02) has elapsed, the brake status "Brake closed [0]" is displayed in 0x2820:015 (P712.15).
⑧	If "Run" is set to FALSE, the motor is stopped with the stop method set in 0x2838:003 (P203.03). In the example: Stop with standard ramp. In this case, closing threshold and closing threshold delay are not effective anymore.