1FT7068 Holding Brake Control with SIMOTION C240 on SINAMICS S120

1. System Overview

The 1FT7068-5AF70-ABB0 is a 1FT7 high-dynamic permanent-magnet synchronous servo motor (frame size 68, stack length 6) equipped with a 24 V DC integral holding brake. It is used in this conversion as a HOIST axis, replacing a previously-ABB-served motor. The new drive train is a SIMOTION C240 motion controller, a SINAMICS S120 CU320-2 DP control unit, a 6SL3120-2TE21-8AA3 Double Motor Module, and the 1FT7 motor. Because the brake coil is integrated into the motor housing and brought out on two dedicated conductors inside the power cable, every segment of the chain — motor → MOTION-CONNECT cable → Double Motor Module → drive firmware → SIMOTION axis — must be correct before SCOUT will report a healthy brake.

The single most important point this field case demonstrates: SIMOTION does NOT switch the holding brake. The brake is opened and closed exclusively by the SINAMICS drive object that physically controls the motor. SCOUT only configures the brake behaviour; SIMOTION only supervises the brake state through the axis status word. If the brake does not open after enabling the drive, the problem is almost always hardware (wiring, cable type, connector, or 24 V supply), not SIMOTION programming.

2. Required Hardware and MLFB Interpretation

Before changing any parameter, validate the hardware in the control cabinet. The order code (MLFB) of the 1FT7068-5AF70-ABB0 decodes as follows:

Because position 14 is "A", this motor is delivered with a built-in 24 V DC holding brake. The brake holds approximately 20 Nm, the coil draws ~1 A (resistance 24-30 Ω), and the brake connection is brought out on two conductors (black + white) inside the same MOTION-CONNECT power cable as the U/V/W/PE power cores. There is no separate "brake cable" — the conductors are integrated.

The full hardware list for the affected drive:

Reference for the MLFB rule and the 1FT7 series catalog: Siemens Industry Online Support, search "1FT7068" to retrieve the current configuration manual and the SIMOTION C240 manual.

3. Root Cause: Power Cable Without Brake Conductors

The alarm encountered in this case (F07990 — "Motor holding brake error") is generated by the SINAMICS drive because the brake circuit is open when the drive expects a closed circuit through the holding-brake coil. The root cause is a power cable that does not contain the two brake conductors.

The drive detects the open brake circuit within ~50 ms of the first enable attempt and raises F07990 with fault value r0949[0] = 2 (brake open, no current flowing). If the cable is shorted, r0949[0] = 3 is reported.

4. Selecting and Wiring the Correct Power Cable

Use the Siemens MOTION-CONNECT configurator to verify the cable. The ordering key for power cables follows the scheme:

6FX 5 0 0 2 – 5 [C|D] [N] [01|11|31] – [length code] [connector code]

For the 1FT7068 with holding brake the correct power cable is 6FX5002-5CN01-1CC0 (or -1BF0, -1BK0, etc. depending on connector preference and length). The cable contains 4 × 1.5 mm² power cores (U/V/W/PE) plus 2 × 1.5 mm² brake cores (black/white), shielded, in a PVC jacket. Drag-chain applications use 6FX5002-5CN11 (PUR jacket) instead. If the existing cable in the cabinet is 6FX5002-5DN31-1BK0, it has only 4 × 1.5 mm² power cores; the brake is therefore physically not connected and F07990 is the correct response. Replace the cable with the 5CN01 variant.

Pinout of the motor-side power connector for the 1FT7 with brake (size 1, M17 Speed-Connect):

The Double Motor Module 6SL3120-2TE21-8AA3 exposes its motor interfaces as follows:

5. Configuring Brake Control in SCOUT

Once the correct cable is installed, configure the brake in SCOUT:

1. Open the SCOUT project and connect to the SIMOTION C240 (online or offline).
2. In the project navigator, expand the SINAMICS_Integrated or S120_CU320_2 drive object that controls axis 1 (the HOIST axis in this case).
3. Right-click the drive object → Open the function navigator (or use the menu Drive → Function navigator).
4. Navigate to Functions → Brake control → Brake.
5. Open Brake configuration.
6. Select [1] Motor holding brake acc. to sequence control.
7. Confirm with OK; SCOUT writes p1215 = 1 to the drive offline.
8. Click the toolbar button RAM to ROM for persistent storage of all parameters.
9. Click Download (or Target system → Download) to push the project to the SIMOTION C240 and the CU320-2.
10. Perform a power-on reset of the drive (or issue p0970 = 1 from the expert list) to make the new brake configuration active.

Internally, this writes p1215 = 1 into the drive, enables the integrated holding brake as a sequence-controlled element, and loads the brake timing values from the motor record (p1216, p1217, p1218). For a SIMOTION C240 the SCOUT project must use SIMOTION SCOUT V4.4 SP1 or higher (V5.x recommended) with a compatible drive firmware on the CU320-2. The C240 firmware V4.4.x paired with SINAMICS S120 firmware V4.8.x is a typical validated combination for this type of retrofit. When commissioning a fresh C240, prefer SIMOTION SCOUT TIA V5.2 SP1 with S120 V5.2.

6. SINAMICS S120 Brake Parameters

The brake parameters are written into the drive automatically when the motor is selected from the motor list (p0301 = 1708, p0302 auto-detected from encoder). The full brake-related parameter set is:

The brake status can be observed online in SCOUT under Control diagnostics → Status words → r0899 bit 12 (drive-internal) and via the SIMOTION axis status bit _actAxisState.brakeState in the user program. A TRUE brakeState bit means the drive has applied 24 V to the brake coil and the brake is OPEN; a FALSE means the coil is de-energised and the brake is mechanically closed.

7. Brake Sequence and Timing

The integrated sequence control closes the brake before the pulses are cancelled on a stop command, and opens the brake only after the drive is enabled and torque has been established. The standard sequence is:

1. SIMOTION issues _enableAxis() → ON command to drive (r0899.0 = 1).
2. SINAMICS energises the motor (magnetising current ramp, typically 50-200 ms).
3. After p1216 (release time, 200 ms) the internal brake contactor closes, applying 24 V to the holding brake coil.
4. After p1218 the drive checks that the brake has opened (current feedback on BD+/BD-).
5. SIMOTION begins motion (_pos, _velocity commands).
6. On _disableAxis() or OFF1, drive ramps speed to zero along the ramp generator.
7. When n=0 is detected (p1227 timeout), drive waits p1228, then removes the 24 V from the brake coil.
8. Brake mechanically closes during p1217.
9. Drive pulses are cancelled; power-up of the axis is reset.

For OFF2 (immediate stop) the drive cancels pulses immediately and removes brake voltage in the same cycle, producing an "emergency" brake close. For OFF3 (rapid stop) the drive ramps quickly to zero and uses the normal sequence. Vertical-axis hoist applications should use OFF2 for STO/SS1 because any delay during a stop command can cause load drop. Wire the SIMOTION safety signal to the SINAMICS safe stop input (X130 EP terminal on the CU320-2) so that a stop category 1 takes the brake close in < 30 ms.

8. F07990 Diagnosis and Clearing

F07990 is the canonical fault for "motor holding brake error". The fault value in r0949[0] provides the precise reason:

A07991 ("Motor holding brake warning") may be raised in parallel, indicating that the drive has detected a brake-related condition that is not yet a fault (for example, brake wear counter threshold reached). To clear F07990:

1. Power off the drive (24 V control voltage remains for diagnostics).
2. Inspect the motor power connector; verify the brake wires are present at the motor side (check the cable MLFB — it must be 6FX5002-5CNxx).
3. Measure brake resistance at the Motor Module side of the cable (between the BD+ and BD- pins on the integrated brake terminal block).
4. Check the brake 24 V supply at X124 of the Motor Module (terminal 1 = 24 V, terminal 2 = 0 V; must be 20.4 – 28.8 V DC).
5. Replace the cable if wires are missing.
6. Power the drive, acknowledge the fault with p3981 = 1 (or SCOUT toolbar "Acknowledge faults"), and re-enable.

9. Vertical Axis (Hoist) Safety Considerations

A HOIST axis — as in this ABB → Siemens conversion — is a vertical load-bearing axis where the holding brake is a primary safety element, not a parking brake. The following rules apply:

• The holding brake must be rated for at least 1.5 × the static load torque at maximum payload (the 1FT7068 holding torque of 20 Nm covers a 200 kg load at a 100 mm winch radius).
• OFF2 (immediate pulse cancel + brake close) must be the default stop for STO/SS1 in the safety program.
• The SIMOTION _enableAxis command must not be issued until the drive confirms the brake is open (r0899.12 = 1 AND the brake current feedback is within tolerance).
• Monitor _actAxisState.brakeState in the SIMOTION program; raise an E-Stop if the brake state and the drive enable state disagree for more than 500 ms.
• Configure p9601 / p9801 (SI enable) and p9650 / p9850 (SI F-DI force stop) to integrate the brake into the safety chain. Wire a 1-channel or 2-channel safe input to the CU320-2 X130 EP terminal.
• Implement a load-side overspeed check independent of the drive (e.g. external speed switch on the gearbox output shaft) to catch cases where the drive enable is lost without the brake engaging.
• Test the brake with a known payload before placing the hoist in production. The holding torque test (load × lever arm) should be performed with the drive disabled and the brake engaged for at least 5 minutes; the load must not move more than 1 mm.

Never rely on the SIMOTION PLC to "close the brake" by writing a digital output or a tag. The brake must be closed by removing the drive enable, so that SINAMICS uses its tested OFF2 sequence. The drive monitors BD+/BD- current and can detect a stuck contactor; the PLC cannot.

10. Commissioning Verification Checklist

Walk through this list before placing the hoist in service:

1. Motor power cable is 6FX5002-5CNxx (with brake conductors). Cross-check the MLFB stamped on the cable jacket.
2. Brake coil resistance measured at the Motor Module side reads 24 – 30 Ω (allow 20 – 35 Ω for cold/hot variation).
3. Brake wires are continuous to the BD+/BD- pins of the motor power connector (no opens, no shorts to PE).
4. No short between brake wires and PE (megger test at 500 V DC, > 10 MΩ).
5. 24 V supply on X124 of the Motor Module is present and stable (20.4 – 28.8 V DC, ripple < 5 %).
6. DRIVE-CLiQ cable 6FX5002-2DC10-1BK0 is connected motor encoder to X202 (and the second axis to X203).
7. SCOUT shows the correct motor (1FT7068-5AF70-ABB0) in p0301 and the encoder in p0400.
8. p1215 = 1 selected via SCOUT Brake Configuration → "Motor holding brake acc. to sequence control".
9. Drive firmware on CU320-2 matches SIMOTION C240 compatibility list (S120 V4.8+ for SIMOTION V4.4+; S120 V5.2+ for SIMOTION V5.2).
10. RAM-to-ROM executed; project downloaded; power-on reset performed (p0970 = 1).
11. Manual enable: _enableAxis → brake opens (audible click + r0899.12 = 1) within 300 ms.
12. Manual disable: _disableAxis → motor stops, brake closes, drive pulses cancel.
13. OFF2 test: drive pulses cancel within 5 ms, brake closes within 30 ms, vertical load holds.
14. Fault injection: disconnect brake wire → F07990 with r0949[0] = 2 → re-connection clears with p3981 = 1.

Once all 14 items pass, the SIMOTION program can take over the hoist control with confidence that the brake is hardware-validated. The original F07990 alarm in the field case described in the introduction is resolved by replacing the 5DN31 power cable with the 5CN01 variant; no parameter change is required beyond the standard brake configuration sequence shown in section 5.

11. Troubleshooting Matrix

FAQ