FCB 21 Brake test

FCB 21 tests the function and performance of up to 2 brakes for each inverter. The function generates a configurable torque against the applied brake (static test). Movement within a configured limit is permitted. For systems with two brakes, both brakes are tested separately – first brake 1 and then automatically brake 2. The brake test is compatible with motor brakes and external brakes.

In safety systems, diagnostics may be required by standards, e.g. EN ISO 13849-1. The FCB 21 brake test is suitable as a diagnostic function for safe brake systems up to performance level e (PL e). The safety-related subfunctions involving brakes – safe stopping (SBA) and safe holding (SBH) – are reliably diagnosed by the FCB 21 brake test. A review by TÜV Nord confirmed the suitability of FCB 21 for safety systems. For the safety assessment, a diagnostic coverage of DC = 90% (DC = diagnostic coverage) can be assumed for the FCB 21 brake test diagnostic function.

The brake test can be optimally adapted to a wide range of application requirements. Status messages are available as feedback, as well as the test results "passed" (test result OK) and "failed" (test result NOK) for each brake separately. The test result "OK" indicates that no movement or only movement below the permissible limit was detected during brake testing. Optionally, additional test results, such as measured torque and movement values, can be used.

In gravity-loaded axes, the test torque for the brakes is the sum of the current application load torque and the torque additionally generated by the motor. The load torque in systems often varies depending on the load condition or the position at which the brake test is performed. In such cases, the load torque is unknown when the brake test is started, making it more difficult to configure the brake test to meet the application requirements. With the FCB 21 brake test, you can either specify a fixed load torque or use the integrated automatic load detection of FCB 21. The automatic load detection in particular significantly simplifies startup and provides greater flexibility. Automatic load detection ensures that the brakes are tested with the configured test torque, even if the load torque in the application varies from one test to another.

FCB 21 is compatible with drive train 1 (DT 1). The motor must be started up using the VFC^PLUS or CFC control mode. This requires a motor encoder that is suitable both for the control mode and for the position control/position hold control function. During an active brake test, movement is detected and monitored via the motor encoder. If a distance encoder is also enabled in the control loop for DT 1, the brake test can monitor the maximum permitted movement using either the motor encoder or the distance encoder.

The use of HTL encoders via digital inputs (counter inputs) is not recommended for the FCB 21 brake test, for example with MOVITRAC^® advanced, as a possible failure of an encoder track signal would not be detected. This can result in a test outcome of "OK" even if the motor moves beyond the limit during an active brake test. For this reason, it is preferable to use encoders connected to the inverter’s encoder interface or via MOVILINK^® DDI.

The brake(s) can be controlled as follows: