SINAMICS S120 Holding Brake Control via SIMOTION C240 PROFIBUS

Problem Statement: Crane Hoist Brake with Safety Gate

On a crane hoist application, a 1FT7068-5AF70-ABB0 Siemens synchronous servo motor with an integrated 24 V DC permanent-magnet holding brake is commanded by a SIMOTION C240 motion controller via PROFIBUS DP through a SINAMICS S120 Control Unit (CU320DP) and an 18 A single-axis Motor Module (6SL3120-2TE21-8AA3). The motor drives a hoist that lowers packaged tiles to operators on the shop floor. A safety gate must prevent a load from being lowered onto personnel, which means the holding brake must close (engage) immediately whenever the gate is opened, and remain released (lifted) only when the gate is closed and the drive is actively controlled.

The user-observed issue is that the brake logic is not defined yet, and the project is mid-commissioning. The brake, by Siemens design, is not controlled directly by SIMOTION application code. Instead, the SINAMICS S120 controls the brake using its internal sequence control, and SIMOTION exchanges brake-relevant commands through the PROFIBUS telegram. A free digital input on the CU320, DI3 (terminal X122.4), is wired to the safety gate contact and must be used as part of the brake release / close decision through BICO interconnection.

System Overview and Hardware Architecture

The drive topology is a classic SIMOTION-over-PROFIBUS architecture with the SINAMICS S120 as the intelligent drive periphery.

The CU320DP hosts the SERVO drive object for the hoist axis. SIMOTION C240 sends motion setpoints and control words through PROFIBUS DP using a configurable Siemens telegram (commonly Telegram 105 for a 16-bit position interface, or Telegram 106 for the 32-bit position interface). The SINAMICS internal brake sequencer decides when the brake opens (during run-up) and closes (during stop or fault). The DI3 input on the CU320 can be wired into the brake logic through BICO without consuming any PROFIBUS telegram bandwidth.

Prerequisites

1. SINAMICS S120 firmware compatible with the 6SL3120-2TE21-8AA3 Motor Module; install the matching Support Package in SIMOTION SCOUT (or in TIA Portal with Startdrive).
2. Motor commissioned electronically: either enter the motor code (p0301) manually for the 1FT7068-5AF70-ABB0 or rely on the DRIVE-CLiQ electronic nameplate (preferred).
3. PROFIBUS DP cable installed between SIMOTION C240 and CU320DP; both ends terminated; baud rate matched on the master and the slave (typically 1.5 Mbps or 12 Mbps).
4. Safety gate contact wired to a free digital input on the CU320; here DI3 (X122.4) is used.
5. Motor holding brake supply: confirm the ABB0 brake variant is the 24 V DC version and that the Motor Module provides the configured brake output (default on X1, sometimes via an external Brake Module on the cabinet).
6. STARTER or SIMOTION SCOUT commissioning tool online to the CU320DP, with control authority granted.

SINAMICS Holding Brake Parameter Reference

Configure the motor holding brake under the SERVO drive object. The most relevant parameters and their typical use for a 1FT7 motor with integrated permanent-magnet brake are listed below.

Brake Configuration in SINAMICS (Step-by-Step)

1. In SIMOTION SCOUT, open the project, navigate to the CU320DP and select the SERVO drive object for the hoist axis. Switch online with control authority.
2. Open the configuration mask Drive > Functions > Brake Module / Motor Holding Brake (or Configuration > Drives > Brake Module depending on tooling). Confirm the holding brake function is enabled - this sets p1215[0] to 1 (sequence control) or 3 (with PROFIBUS command).
3. Enter the opening time (p1216) and closing time (p1217) for the 1FT7068-5AF70-ABB0 brake from the motor data sheet.
4. Configure the speed thresholds p1218 and p1219, and the standstill delay p1220. For a hoist, leave p1219 = 0 and increase p1220 so the drive comes fully to rest before the brake closes; this prevents brake wear and audible impact.
5. Select the BICO source for the close command (p1225). For a safety-gate-driven close, interconnect p1225 to the inverted status of DI3 (see next section).
6. Save the project to the ROM of the CU320DP so the parameters survive power-down.

Refer to the Siemens external-motor-holding-brake documentation for the canonical parameter mask and the meaning of each field:

TIA Siemens Cloud: External motor holding brake - F-TM Servo Drive HF

BICO Wiring for DI3 Safety Gate Integration

The DI3 input on the CU320DP is wired to the safety gate contact. CU320 terminal X122 has the following assignment relevant to this application:

The signal r723.3 reports the (non-inverted) status of DI3, and r723.0..7 are the bits of the DI0..DI7 word. To close the brake when the gate is open (DI3 = HIGH in this wiring) use the inverted input via r723.3 or via the inverter block p2024.x. The expert in the source thread recommends using the inverted status word bit (r723.3) for the closing command so that a HIGH level on DI3 - representing gate-open - forces the brake closed.

Use the Starter/Scout BICO editor to interconnect:

p1225[0]   = r723.3          // close brake on DI3 HIGH (gate open)
p0840[0]   = r722.0          // ON/OFF1 from drive enable (PROFIBUS STW1.0 OR'd with master enable)
p0852[0]   = 0               // enable operation from STW1.3 only
r723.0..7  = status of CU320 digital inputs

If the wiring polarity in the panel is reversed (gate-open = LOW), drop the inverter and use r723.3 directly with a downstream AND against the internal brake-close condition.

PROFIBUS Telegram Selection on CU320DP

Select the PROFIBUS telegram for the SERVO DO. Common choices for a hoist with position control:

Configure the telegram in two places: under the PROFIBUS slave properties on the CU320DP and under the SIMOTION axis configuration. SIMOTION uses the same telegram number for the receive/transmit slot length. After changing the telegram, download both sides of the PROFIBUS configuration.

With Telegram 105 the relevant control bits from SIMOTION to SINAMICS are:

SIMOTION C240 Application Logic (MCC / LAD)

The MCC chart on the SIMOTION C240 commands the hoist axis and exchanges the STW1/ZSW1 bits over PROFIBUS. Below is the canonical ST code skeleton for the brake interlock on a safety gate. Adapt the variable names to the project's tag naming.

// MCC ST snippet - hoist axis with safety gate interlock
// Input:  bSafetyGateClosed : BOOL  ; TRUE when safety gate is closed
// Output: bAxisEnable        : BOOL  ; OR'd into STW1.0 / STW1.3 on PROFIBUS
//         bBrakeForceClose   : BOOL  ; pulsed to p1225 via DPV1 or kept in PLC

IF bSafetyGateClosed THEN
    bAxisEnable        := TRUE;     // permit ON/OFF1 and Enable operation
    bBrakeForceClose   := FALSE;    // SINAMICS internal sequencer manages release
ELSE
    bAxisEnable        := FALSE;    // OFF1 + drop enable -> drive ramps to zero -> brake closes
    bBrakeForceClose   := TRUE;     // belt-and-braces close via DI3 path
END_IF;

// Optional: torque proving before brake release
IF bAxisEnable AND (ABS(r_act_speed) > p1218_threshold) THEN
    bBrakeReleaseOK := TRUE;
END_IF;

The same logic can be expressed as ladder (LD) using a normally-closed contact on bSafetyGateClosed wired into the axis enable rung. The key point - confirmed by Siemens application engineering - is that SIMOTION does not toggle the brake output pin directly; it commands the drive state (enable / disable / stop), and SINAMICS closes the brake based on the resulting state plus the BICO-wired DI3 path.

Brake Timing for Hoist Load Holding (Anti-Rollback)

For hoisting applications the brake opening time is critical. During p1216 the drive must build torque before the mechanical brake fully releases, or the load will roll back. Configure a torque-proving step:

1. At motion start, command ON/OFF1 (STW1.0 = 1) and Enable operation (STW1.3 = 1).
2. Watch r0079 (torque actual value) and r0089 (sequence control status, bit 0 = brake released).
3. Hold STW1.4 (reject ramp) or do not issue a positive speed setpoint until r0079 reaches p1525 (torque threshold for brake release).
4. After p1216 has elapsed and r0899.12 = 1 (brake released), release the setpoint normally.

On stop, clear ON/OFF1 (STW1.0 = 0). The drive ramps down per p1121 (OFF1 ramp). When the speed reaches p1218 and after p1220 standstill, the SINAMICS closes the brake. The safety-gate path (DI3 HIGH) can short-circuit this sequence by interconnecting p1225 to the DI3 source, which closes the brake regardless of speed.

Task Lifecycle: Stop, Start, Resume SIMOTION Tasks

During commissioning, the user also wants to stop a SIMOTION task and resume it later. Use the standard MCC / ST system functions on the C240:

Use _suspendTask / _resumeTask only when you want to preserve the call-point state. For a hard commissioning interlock on the hoist axis, prefer _stopTask / _startTask because the suspended-task mechanism keeps the prior program state which can re-engage the drive unintentionally.

Commissioning Verification and Acceptance Test

1. With the drive offline, verify the BICO wiring using the Starter/Scout signal chart on the Brake Module mask: toggle the simulator bit for DI3 and observe p1225 status, r0899.12 (brake released), and r0046.27.
2. Power up the drive, enter the safety gate state with the gate closed, command ON/OFF1 from SIMOTION, and confirm in the Starter trace that the brake opens after p1216 and torque builds above p1525.
3. With the gate closed, command a small lift (10 cm), then OFF1; confirm that the brake closes after p1220 and the load is held. No rollback should be visible on the position trace.
4. Open the safety gate (DI3 HIGH). Confirm the drive is disabled (STW1.0 / STW1.3 reset) and the brake is closed. Attempting to start the drive from SIMOTION should be inhibited because the gate-closed condition is missing.
5. Force a drive fault (e.g., by unplugging the encoder). Confirm the brake closes immediately via the fault path (OFF1 / OFF2 behaviour) and the load does not drop.
6. Perform a load-hold endurance test: load the hoist to its rated mass, command hold, observe temperature rise on the brake (within motor data sheet limits) and current draw on the Motor Module.

Troubleshooting Matrix

Frequently Asked Questions