Troubleshooting SINAMICS S110 Fault 7930: Brake Control Error

Problem Overview: SINAMICS S110 Fault 7930 on CU305 / PM340 Systems

The SINAMICS S110 servo drive family, when paired with a Control Unit CU305 DP (order number 6SL3040-0JA00-0AA0) and a PM340 power module (example: 6SL3210-1SE17-7AA0, firmware E02), uses an external holding-brake control path that is fundamentally different from integrated control units such as the CU310 or CU320. On PM340-based blocksize drives the motor holding brake is not driven directly by the Control Unit. Instead it requires a separately mounted brake relay module on top of the PM340 power module, fed from a Control Unit digital output (DO) and wired to the motor brake coils via dedicated brake conductors (BD+ / BD-) inside the motor power cable.

When this path is missing, misconfigured, or wired to the wrong terminals, the drive raises F07930 "Drive: Brake control error" with a sub-fault value (commonly 10). The BOP20 basic operator panel shows the same fault number, and the drive refuses to enable — the alarm "The switch-on disable of the drive is active" is displayed, blocking commissioning, jog operation, and any speed/torque profile run.

This reference documents the diagnosis and correction procedure for F07930 specifically on the S110 / CU305 / PM340 / 1FK7 motor combination. It also covers the related fault F01030 (sign-of-life failure / measurement timeout during automatic speed-controller tuning) and the digital-input wiring on X132 / X133 that frequently accompanies the same commissioning session.

System Identification and Pre-Check

Before chasing F07930, confirm the exact hardware stack. Several hardware variants follow the same diagnostic path but require different remedies.

Verify each item in STARTER under Online > Drive Unit > Topology or in Startdrive under Device configuration > Hardware catalog. A mismatch between the offline configuration and the actual device will not cause F07930 directly but it produces commissioning aborts that mimic a brake-control fault.

Root Cause Analysis: Why F07930 Triggers

Fault F07930 is generated by the internal brake-control state machine in firmware E02. The drive continuously checks whether the holding brake is responding to commands issued through parameter p1278. When the brake control is enabled (default p1215 = 0 = no brake, or p1215 = 1 = integrated brake controlled by the CU itself, which is invalid on PM340), the firmware expects feedback within a defined time window. The sub-fault value (10) indicates:

• The brake was commanded to close (or open) by the CU.
• The expected acknowledgement / current signature was not detected within the configured monitoring time.
• The drive enters the safe-state switch-on disable and latches F07930.

On a PM340 system the most common root causes are:

1. No brake relay installed. The PM340 has no built-in brake switching element. BD+ / BD- from the motor cable must land on the brake relay's output, which in turn switches 24 V onto the brake coil.
2. BD+ / BD- wires landed on R1 / R2. R1 and R2 are the external braking resistor terminals, not the motor-holding-brake terminals. Connecting BD+ / BD- here can damage the resistor, blow fuses, or — at minimum — never energize the brake, so the brake-control monitoring trips.
3. Brake relay present but no DO BICO connection. Parameter p1215 = 3 selects "External brake control via BICO". When this is selected without a BICO connection from a free DO (for example r899.12) to the brake-control input, the drive issues commands that no hardware can execute.
4. Motor without brake, but firmware configured for brake. If the connected motor is the non-brake variant (suffix 1UH1 rather than 1UH3) and p1215 is not set to 0, F07930 is the expected result.

Distinguishing F07930 from Related Drive Alarms

Several alarms share the same "switch-on disable" surface symptom. Use the table below to localize the real cause before changing parameters.

Solution Step 1: Identify Whether the Motor Has a Holding Brake

The motor order number 1FK7044-7AH71-1UH3 ends with 1UH3. On the 1FK7 motor family the final block encodes the mechanical options:

Confirm the label on the motor nameplate matches the configured motor in STARTER (p0300 / p0301). If the wrong motor is loaded, F07930 is a secondary effect.

Solution Step 2: Install the PM340 Brake Relay

For PM340 blocksize power modules, the motor holding brake must be driven through the dedicated brake relay module that snaps on top of the PM340. Detailed mechanical and electrical description is in the PM340 Device Manual, Chapter 7.5 (reference: SINAMICS S110 / PM340 Equipment Manual (Siemens Support entry 26508917)).

1. Order the matching relay: for PM340 frame FSA–FSC, the brake relay is 6SL3252-0BB00-0AA0.
2. Mount the relay on top of the PM340 following the device manual mechanical drawing.
3. Wire the relay's 24 V control input to a free digital output on the CU305 (for example DO 0 at X132, or X131 depending on CU305 variant).
4. Wire the relay's high-current output to the BD+ / BD- conductors of the motor power cable (typically 2 × 1.5 mm², shielded pair).
5. Do not connect BD+/BD- to R1 / R2; those are for an external braking resistor (used for regenerative energy dissipation under heavy deceleration).

Solution Step 3: Configure Brake Parameters in STARTER / Startdrive

Once the brake relay is mounted, configure the firmware to expect an external brake:

Example BICO interconnection (STARTER notation):

p1215 = 3          (External brake control)
p1278 = 0          (Disable diagnostic, only if no feedback signal available)
p0855.CI = r722.x  (DO source for "open brake")
p0858.CI = r722.y  (DO source for "close brake")

If the brake relay is the Siemens-branded module, the integrated brake control of SINAMICS assumes a fixed 24 V armature switching path, and no additional BICO is required beyond p1215 = 3. With a third-party relay, BICO from the DO is mandatory.

Solution Step 4: Wire the CU305 Digital Inputs Correctly (X132 / X133)

On the CU305 DP the default terminal layout is:

If X132 reacts to 24 V (terminal evaluation visible, LED on) but X133 does not:

1. Verify that the X133 group has its own 24 V supply pin energized — some CU305 variants share 24 V across X131, others require X133 to be powered separately.
2. Check the BICO interconnection of the digital-input function in STARTER: confirm that the status word r722 bit position matches the terminal you are wiring. Common mistake: configuring r899.12 as the source for an input that is physically r722.0. r899 is a status word; r722 is the digital-input image.
3. Confirm in STARTER Inputs/Outputs > Digital inputs that the relevant DI is set to "Active high" (default) or "Active low" matching your switch wiring.

Solution Step 5: Clear the Latched "Switch-On Disable" and Acknowledge F07930

After correcting the wiring, F07930 must be acknowledged before the drive can run. On the BOP20:

1. Navigate MENU > FAULTS > F07930.
2. Press the OK button to view the sub-fault value (10) and timestamp.
3. Press ACK to acknowledge. If the fault has a "SHIFT" requirement (safety lock), cycle the Control Unit power.
4. On the same menu, inspect F07930: ACTIVE / CLEARED. It must show CLEARED before OFF1 / OFF2 / OFF3 will release.

In STARTER, click Control panel > Assume control priority and increase the control-priority timeout from the default 1000 ms to 4000–5000 ms. A short timeout is the typical cause of the secondary F01030 that aborts the automatic speed-controller measurement: the master (STARTER) loses "control priority" mid-measurement, the drive drops OFF1, and the sign-of-life monitor trips F01030.

Solution Step 6: Re-run Automatic Speed-Controller Measurement

F01030 during the speed-controller optimization routine typically indicates either:

• Control-priority timeout too short — increase as described in Step 5.
• Mechanical load cannot follow the test trajectory — typical for pedal-robot or back-driven pedal mechanisms where the human-load oscillates the motor. Reduce the test-travel limits or run the measurement in a "decoupled" state.
• Encoder or motor identification not yet completed — repeat Motor identification > Standstill measurement first, then run Speed-controller tuning.

1. Open STARTER > Commissioning > Control structure > Speed controller.
2. Click Assume control priority, set timeout to 5000 ms.
3. Run Optimization > Automatic speed-controller tuning.
4. Monitor r1407 (speed-controller status) and r0062 (speed setpoint) during the test.
5. If F01030 still occurs, reduce dynamic factor p1465 and mechanical moment of inertia p1498 before repeating.

Verification Checklist

Preventive Measures for Future Commissioning

• Document brake hardware. When ordering the motor, order the brake relay and the matching motor power cable with BD+ / BD- conductors at the same time.
• Use a check-list. Before the first commissioning power-up, verify R1/R2 are reserved for the external braking resistor and BD+/BD- are landed on the brake relay only.
• Disable brake monitoring only with reason. p1278 = 0 is a valid workaround for legacy installations, but loses diagnostic coverage — write a comment to p1278 in the project notes explaining why.
• Always run motor identification before speed-controller tuning. F07930 / F01030 are common side effects when identification is skipped.

Frequently Asked Questions