What it means
A01781 ("SBT brake opening time exceeded") is raised during the Safe Brake Test (SBT) when the brake has not opened after the maximum permitted time of 11 s. The manuals for G130, G150, S120 and S150 describe this alarm with identical wording.
Why it appears
- During the brake test the drive went into a fault condition and therefore closed the brake.
- For an external brake, the feedback signal "Brake closed" was signaled too long (p10230.5, p10235).
What to check
- Read the alarm value in r2124 as a binary number to determine whether the internal or the external brake could not be opened (see the alarm value decoding below).
- Carry out a safe acknowledgment.
- Restart the brake test via p10230.1 / p10235.1.
Reading the message value
- The drive enters the alarm cause as a binary value ("Fault cause: %1 bin") into the alarm value r2124.
- Bit 0 = 1: Internal brake was not able to be opened.
- Bit 1 = 1: External brake was not able to be opened.
Parameters the manual names
- p10230 (BI: SI Motion SBT control word / SBT STW) — bit 5 is referenced for the "Brake closed" feedback of the external brake; setting bit 1 = 1 restarts the brake test.
- p10235 (CI: SI Safety Control Channel control word S_STW3B / SCC S_STW3B) — named together with p10230.5 for the external brake feedback; setting bit 1 = 1 also restarts the brake test.
- r2124 (Alarm value) — holds the alarm cause of this alarm in binary form: bit 0 internal brake, bit 1 external brake.
Acknowledging and restarting
The manual's remedy consists of two steps: carry out a safe acknowledgment, and restart the brake test via p10230.1 / p10235.1.
The same on every family
Every manual that describes A01781 gives it the same reaction, acknowledgement and message class.
| Drive family | Reaction | Acknowledge | Message class | Component | Manual |
|---|---|---|---|---|---|
| S120, S150 | NONE | NONE | Safety monitoring channel has identified an error (10) | None | SINAMICS S120, S150 List Manual · p. 2701 |
| G130, G150 | NONE | NONE | Safety monitoring channel has identified an error (10) | None | SINAMICS G130, G150 List Manual · p. 1481 |
The drives this code lives on
A01781 is described for G130, G150, S120, S150. These are the converters of those families in our catalogue — price on request.
Questions technicians ask
What does alarm A01781 SBT brake opening time exceeded mean?
During the Safe Brake Test (SBT) the brake did not open within the maximum time of 11 s, so the drive raised this alarm.
What causes A01781?
Either the drive went into a fault condition during the brake test and therefore closed the brake, or, for an external brake, the feedback signal "Brake closed" (p10230.5, p10235) was signaled too long.
How do I clear A01781?
Carry out a safe acknowledgment and then restart the brake test via p10230.1 / p10235.1.
How can I tell whether the internal or the external brake could not be opened?
Interpret the alarm value in r2124 binary: bit 0 = 1 means the internal brake could not be opened, bit 1 = 1 means the external brake could not be opened.
Codes next to this one
Source
Written from Siemens' own List Manuals and operating instructions; every number, designation and parameter on this page is checked against them before publication.
All SINAMICS codes: fault and alarm codes · the A01xxx group · SINAMICS manuals · Siemens manuals