Siemens 1FK7042 Servo Motor Brake Retrofit on SINAMICS S110

Overview

This reference covers a common retrofit scenario: upgrading a Siemens SIMOTICS S-1FK7 servo motor from a non-braked variant to a braked variant on an existing SINAMICS S110 drive. The specific conversion replaces article number 1FK7042-3BK71-1RA0 with 1FK7042-3BK71-1RB0 on a CU305 control unit. The retrofit is typically motivated by machine-safety requirements, such as eliminating coast-down on safety light-curtain trips or on E-stop events.

Two engineering tasks are required: configuring the holding brake through drive parameter p1215, and wiring the brake conductors from the Motion Connect cable to the drive or to an interposing relay. Encoder configuration does not change because the encoder is identical between the two motor variants. The drive does not have to be fully recommissioned, but the change to a brake variant does require brake-specific configuration in the parameter set.

Motor Identification: 1FK7042 Family and Suffix Codes

The 1FK7 series is the SIMOTICS high-precision servo motor family. The 12-digit article number encodes frame size, winding, feedback, brake option, and shaft detail.

The change from RA0 to RB0 indicates the new motor carries a 24 V DC spring-applied holding brake. Mechanical dimensions, flange, shaft, and feedback type are preserved across the two article numbers. The rotor inertia differs slightly because of the integrated brake rotor, which the drive's auto-identification routine absorbs on the next power-on.

The encoder (typically an EnDat or DRIVE-CLiQ absolute encoder in the 1FK7 family) is unchanged. No encoder reconfiguration is required in the drive project.

Replacement Strategy and Mechanical Equivalence

Siemens generally states that a motor with the same article number can be replaced without recommissioning the drive, as the drive stores the motor parameters in non-volatile memory and reads the electronic type plate on the next power-on. This principle is referenced in the Siemens Industry Online Support article Replacing the motor - SINAMICS S210 / SIMOTICS S-1FK2 (ID 109760645). The same principle applies to the 1FK7 family on the SINAMICS S110.

When the article number changes, as in this RA0 to RB0 case, two additional steps are necessary:

1. Activate the holding brake control through parameter p1215.
2. Wire the brake conductors in the Motion Connect cable to a drive output, an interposing relay, or a brake-enabled power module output.

The drive's motor data (stator resistance, leakage inductance, torque constant, encoder resolution) is read from the motor's electronic type plate via EnDat or DRIVE-CLiQ, so manual motor parameter entry is not required. The auto-tuning routine does not have to be re-executed unless the application is highly sensitive to the small inertia change introduced by the brake rotor.

Parameter p1215: Motor Holding Brake Configuration

Parameter p1215 in the SINAMICS parameter set is the master switch for the motor holding brake. The value is read by the drive's brake sequence control.

Set p1215 = 1 to use the integrated brake sequence control. With this setting the drive automatically engages the brake on OFF1, OFF2, and OFF3 stop commands, and the brake is released when the drive enables the power unit and the speed setpoint is non-zero. The brake release is sequenced with the magnetization build-up, and the brake engagement is sequenced with the standstill detection.

If the brake must be released for manual movement during commissioning or service, set p1215 = 2 temporarily and restore p1215 = 1 before returning the machine to production. Setting p1215 = 2 removes the safety-relevant automatic brake engagement.

SINAMICS S110 and CU305 Hardware

The SINAMICS S110 is a single-axis servo drive. The CU305 is the Control Unit that hosts the firmware and provides the encoder interface, digital I/O, and PROFINET or PROFIBUS connectivity. The power module (typically a PM340 in block, booksize, or chassis format) is connected downstream of the CU305.

Connectors on the CU305 used in this retrofit:

On the CU305 the motor power connector is keyed to accept the power and brake conductors of a Siemens pre-fabricated Motion Connect cable. The pinout is fixed: the brake leads are routed to specific pins on the connector. Consult the SINAMICS S110 Manual, section "Connection of the Motor", for the exact pin assignments on the cable connector that mates with the drive side.

Brake Cable: 6FX5002-5DG01-1BF0 Wiring

Siemens part number 6FX5002-5DG01-1BF0 (ordered as the pre-fabricated assembly SP6FX5002-5DG01-1BF0) is a pre-fabricated Motion Connect 500 power cable with brake conductors. The 5DG segment of the part number identifies the cable family that includes the two brake cores. The 01 segment is a length code; BF0 indicates the connector type on the motor side and the drive side.

The cable structure is:

• 4 power cores (U, V, W, PE) sized for the motor's rated current
• 2 brake cores (24 V DC, typical 0.5-1.5 A draw for the 1FK7 frame 42)
• Overall shield with tinned copper braid, minimum 85% coverage
• Outer jacket rated for the cable's specified installation (fixed or drag-chain)

The brake conductor insulation is identified by color. In Motion Connect 500 power cables the two brake cores are black and white. The 24 V DC supply polarity convention is:

Verify the color code against the cable data sheet that ships with the cable. Variant cables (e.g., 6FX8002 for Motion Connect 800 continuous-flex) can use different colors. Always check the data sheet for the specific 6FX part before terminating.

Brake Electrical Connection Options

The 1FK7 holding brake is a 24 V DC spring-applied brake. Energizing the brake releases the shaft; de-energizing the brake clamps the shaft. Two wiring options are common on a SINAMICS S110.

Option 1: Direct connection through the drive's internal brake control

If the S110 is configured with a power module that exposes a dedicated brake output (some PM340 block-format modules provide a 24 V brake output keyed for the motor cable connector), the brake can be energized directly from the drive. The drive's internal logic, when p1215 = 1, switches the 24 V supply on the brake leads and the brake timing is handled by the firmware.

Verify that the drive-side connector accepts a 6FX5002-5DGxx cable with brake cores and that the PM340 has a brake output. Not all power modules include this output. If the power module is not a brake-enabled variant, use Option 2.

Option 2: External relay driven by a digital output from the CU305

This is the most common wiring on a SINAMICS S110 because the drive does not always have a dedicated brake output. The configuration is:

1. Route the brake's 24 V supply (white conductor) through a normally-open contact of an interposing relay (Phoenix Contact PLC-OSC-24DC/24DC/5, Schrack RT series, Finder 55 series, or equivalent with a 24 V DC coil).
2. Drive the relay coil from a digital output on the CU305. The digital output must be BICO-interconnected to the drive's internal brake control signal.
3. Return the 0 V (black conductor) directly to the 24 V supply's M terminal.
4. Add a flyback diode across the brake coil to suppress switching transients (e.g., 1N4007 or a TVS such as P6KE30A, cathode to P24).
5. Fuse the 24 V supply at 1-3 A depending on brake current.

For BICO routing on the SINAMICS S110, the standard signal is r0899.0 (drive enable) for general enable commands, or the dedicated brake command r1229.1 ("energize brake") when the brake is to be controlled independently of enable. The exact BICO target depends on the digital output number assigned. In STARTER or Startdrive, route the brake control to the chosen digital output:

• p0730 = r0899.0 for the first digital output (function: "drive enable")
• Or, for a free digital output, set its BICO source to r1229.1 (brake command)

Commissioning Without an HMI

The original engineering question raises a practical point: how to change p1215 when no BOP or IOP is connected to the drive. Three commissioning paths are available.

Method 1: STARTER commissioning software

STARTER is the legacy commissioning tool for SINAMICS drives and supports the S110 in all firmware releases. Connect the PC to the CU305 through:

• PROFINET X5 (TCP/IP; assign a unique IP, default 169.254.11.22 if unchanged)
• USB at the CU305 service port (on PM340 blocksize variants)
• RS232 at the CU305 service port (legacy, requires a special cable)

Steps in STARTER:

1. Create a project, insert the CU305 from the online device catalog.
2. Go online, accept the offline/online comparison.
3. Open the parameter list and navigate to p1215.
4. Set p1215 = 1.
5. Set p1216, p1217, p1218 if the brake opening and closing times are non-default.
6. Save the project online: "Load to target device" / "Copy RAM to ROM".
7. Power-cycle the drive to verify the parameter persists across reboot.

Method 2: Startdrive (TIA Portal)

Startdrive is the current commissioning tool, integrated into TIA Portal. It replaces STARTER for new projects. The S110 is supported in Startdrive as of V14 SP1 and later. The procedure is functionally identical to STARTER: connect over PROFINET, navigate to p1215, set the value, and save to ROM.

Method 3: Web server (S110 built-in)

The SINAMICS S110 firmware includes a built-in web server. Access it by entering the CU305's IP address in a browser. The web server exposes the parameter list and a write capability for most adjustable parameters. This is the fastest path when no TIA Portal or STARTER is available on site.

Saving Parameters Permanently

Writing p1215 = 1 only updates the RAM copy of the parameter in the drive. To persist the value across a power cycle, the change must be copied to the non-volatile memory of the CU305. On the S110 the sequence is:

1. Write p1215 = 1 to the drive (RAM).
2. Set p0977 = 1 ("Save all drive parameters to non-volatile memory").
3. Wait for the drive to complete the save (typically 30-60 seconds; the save is indicated by a "Save in progress" state on STARTER or the web server).
4. Do not power-cycle the drive until the save completes.

After the save, cycle the 24 V control supply and confirm p1215 reads back as 1 in the online parameter list.

Brake Timing Parameters

With p1215 = 1 active, the drive sequences the brake based on a set of timing parameters. The defaults for the 1FK7 family are usually correct, but verify them against the motor data sheet that ships with the replacement motor.

When the drive enables (ON command), it does not release the brake until the magnetization build-up is complete and the speed is below p1218. When the drive receives an OFF1, it ramps the speed down, holds the magnetization until standstill is detected, then closes the brake after p1217, then removes the pulses after p1228. Confirm this sequence with a STARTER trace or the web server's signal trace function.

Verification Procedure

After the wiring is complete and p1215 is set, perform the following verification steps before returning the machine to production.

Static verification

1. With the drive in "Ready to switch on" (no enable), confirm the brake is engaged. The shaft must not rotate freely when hand pressure is applied.
2. Apply 24 V directly to the brake leads (disconnected from the drive circuit) and confirm the brake releases. The shaft must rotate freely.
3. Remove the 24 V and re-confirm brake engagement.
4. Reconnect the brake leads to the drive circuit.

Dynamic verification

1. Enable the drive (ON command from the controller).
2. Confirm the brake releases within p1216 ms (audible click and shaft becomes free).
3. Run a slow jog command (10-50 rpm) and confirm direction control.
4. Issue an OFF1 (controlled stop) and confirm the drive ramps to zero, the brake engages, and the shaft holds position.
5. Issue an OFF2 (immediate pulse disable) and confirm the brake still engages through the p1215 = 1 control path. Some safety configurations route OFF2 around the brake control; verify the safety configuration separately.
6. Trigger the light curtain or E-stop and confirm the drive executes the configured safety stop (STO/SS1) and the brake holds the load.

Persistent verification

1. Power-cycle the 24 V control supply to the CU305.
2. Confirm p1215 still reads 1.
3. Confirm the brake behavior on first enable matches the dynamic verification.
4. Back up the project from the drive (STARTER: "Upload to PG") and store it with the machine documentation.

Troubleshooting Matrix

Notes on Cable and Connector Selection

The cable part number 6FX5002-5DG01-1BF0 is a member of the Motion Connect 500 family. For drag-chain (cable carrier) applications, the 6FX5002 family has a limited flex rating. For continuous-flex applications, the equivalent 6FX8002 family is required. Verify the application against the cable data sheet before purchase.

The 5DG cable family has 4 power cores, 2 brake cores, and 2 control cores (for the temperature sensor and other auxiliary signals). Not all cores are populated at the drive-side connector; consult the cable data sheet for the specific pinout.

Connector designation "BF0" identifies the drive-side connector type. Verify the connector type on the CU305's power connector against the cable data sheet to confirm compatibility. If the cable is intended for a different drive family (e.g., S120), the connector may not mate with the S110/CU305.

Safety Integration Notes

A holding brake on the motor is a category-0 or category-1 stop aid but is not a substitute for the safety function. The Siemens Safety Integrated functions (STO, SS1, SS2, SOS) are realized in the drive firmware and are independent of the holding brake. For the retrofit described here, the light-curtain input must be wired to the safety input of the drive (e.g., via PROFIsafe on PROFINET or through a hard-wired safe input on the CU305) and the safety function must be configured in the safety program. The brake then engages as a consequence of the safety stop, not as a replacement for it.

Verify the holding torque of the 1FK7042 with holding brake against the application's required holding torque. The data sheet lists the holding torque for the brake; if the load can exceed it under a worst-case fault, an additional mechanical brake (spring-set, redundant) is required.

FAQ