A01784 — SBT brake test canceled with fault

The safe brake test was canceled as a result of a fault. A01784 tells the technician that the drive has canceled the Safe Brake Test (SBT) because a fault occurred. The cause is not output as text: the drive stores it as an alarm value in r2124, which must be interpreted in binary — each set bit names the condition that led to the cancellation. The manuals for the G130, G150, S120 and S150 print the same bit assignments for this message, so the decoding below applies to all of them.

• The safe brake test was canceled as a result of a fault; the bits set in the alarm value r2124 identify the condition that ended the test.
• Bits 18 to 26 report direct conditions of the test: brakes that must be open for testing the other brake, brakes not all open, an invalid axis position due to a parking axis, an internal software error, a violated position range with the brake closed, the tested brake opened while the test was active, or a test torque that left its tolerance bandwidth (20 %).
• Bit 17 = 1 reports a fault in the brake test sequence itself; its cause is then given by bits 0 to 10 — for example operation not enabled when the test was selected, an external fault, a stop response (OFF1, OFF2, OFF3) or withdrawn pulse enable (e.g. STO), too high a speed setpoint or actual speed, an incorrect speed controller mode, closed-loop control not enabled, no switchover to the brake test, or a reached torque limit.

1. Read the alarm value in r2124 and interpret it in binary to find the set bit; if bit 17 = 1, use bits 0 to 10 to identify the cause of the sequence fault.
2. Remove the fault cause.
3. Carry out a safe acknowledgment.
4. If required, restart the brake test.
5. If bit 17 = 1 together with bit 6 = 1 or bit 23 = 1: check the brake closing time of the motor holding brake (p1217). If it has been set too low, the brake is closed too late at the start of the brake test — adapt p1217.

The message value carries the fault cause: the drive stores it as the alarm value in r2124, which must be interpreted in binary. The set bits identify what canceled the test:

• Bit 17 = 1: fault in the brake test sequence (cause, see bits 0 ... 10). Cause for alarm value bit 17:
  • Bit 0 = 1: operation when selecting the brake test not enabled (r0899.2 = 0).
  • Bit 1 = 1: external fault occurred (e.g. the brake test that has already started is canceled by the user).
  • Bit 2 = 1: when selecting the brake test a brake is closed.
  • Bit 3 = 1: when determining the load torque a brake is closed.
  • Bit 4 = 1: a fault with a stop response has occurred (e.g. OFF1, OFF2 or OFF3) - or pulse enable was withdrawn (e.g. STO selected or operation no longer enabled).
  • Bit 5 = 1: when selecting the brake test the axis speed setpoint is too high.
  • Bit 6 = 1: the actual speed (r0063) of the axis is too high (e.g. brake does not hold during the brake test).
  • Bit 7 = 1: incorrect speed controller mode (e.g. encoderless speed control or U/f operation).
  • Bit 8 = 1: closed-loop control not enabled or function generator active.
  • Bit 9 = 1: control does not switch over to the brake test (e.g. because PI speed control has not been parameterized).
  • Bit 10 = 1: torque limit reached (r1407.7, r1408.8).
• Bit 18 = 1: the internal brake is closed. It must be open when the external brake is tested (p10202).
• Bit 19 = 1: the external brake is closed. It must be open when the internal brake is tested (p10202).
• Bit 20 = 1: not all brakes are open (p10202).
• Bit 21 = 1: axis position during the brake test not valid due to parking axis.
• Bit 22 = 1: internal software error.
• Bit 23 = 1: the permissible position range of the axis was violated with the brake closed (p10212/p10222).
• Bit 24 = 1: the tested internal brake was opened while the brake test was active.
• Bit 25 = 1: the tested external brake was opened while the brake test was active.
• Bit 26 = 1: during the active brake test, the test torque left its tolerance bandwidth (20 %).

• r2124 (alarm value): stores the message value of this alarm; read it in binary to find the bit that identifies the fault cause.
• p10202 (SI Motion SBT brake selection): selects the brake to be tested; bits 18, 19 and 20 refer to this parameter when a brake that must be open is closed.
• p10212 (SI Motion SBT position tolerance sequence 1) and p10222 (SI Motion SBT position tolerance sequence 2): position tolerances of the brake test; bit 23 points to them when the permissible position range was violated with the brake closed.
• r0063 (speed actual value): the actual speed of the axis; bit 6 reports that this value was too high during the test.
• p1217 (motor holding brake closing time): with bit 17 = 1 and bit 6 = 1 or bit 23 = 1, adapt this time if it was set too low and the brake therefore closes too late at the start of the brake test.

After removing the fault cause, carry out a safe acknowledgment; if required, restart the brake test. If the cancellation was a sequence fault (bit 17 = 1) with bit 6 = 1 or bit 23 = 1, adapt the brake closing time of the motor holding brake (p1217) before restarting whenever it was set too low.