Configuring SINAMICS S120 Vector Ramp Generator via TIA

1. Application Overview

A SINUMERIK 808D ADV controlling a spindle motor above 15 kW cannot drive the spindle directly through the CNC's integrated outputs. In this class of machine, the spindle motor is fed by a SINAMICS S120 modular drive system, and the 808D ADV issues a ±10 V analog setpoint to the S120. The drive must therefore be commissioned as a standalone vector-controlled drive with its own ramp generator, rather than receiving position-controlled motion commands over PROFIBUS or PROFINET.

The hardware in the source application is:

• Control Unit: CU310-2 PN (PROFINET variant)
• Power Module: PM240-2 (blocksize, with integrated line filter)
• Spindle motor: Three-phase induction motor above 15 kW
• Setpoint source: Analog input from 808D ADV main spindle output

This article documents how to configure ramp-up, ramp-down, and ramp smoothing directly on the drive when no PLC is generating the profile, using TIA Portal Startdrive as the commissioning tool. The discussion references the official SINAMICS S120 Function Manual (Entry ID 99472695).

2. Prerequisites

Startdrive V16 introduced explicit support for the CU310-2 PN. Older Startdrive versions may show the CU310-2 as "unknown device" or fail to expose the drive object list.

3. Drive Object Selection: VECTOR vs SERVO

When the drive object is created, the engineer must choose between two closed-loop structures:

For a standard induction spindle with no requirement to exceed 650 Hz output, VECTOR is the correct choice. It exposes the ramp-function generator (RFG) on drive object DO1 by default, which is exactly the behavior needed when no external PLC is shaping the velocity profile.

If the spindle must reach 800 Hz (a common requirement for high-speed milling spindles), change the drive object type to SERVO. With SERVO at 4 kHz pulse frequency the drive achieves 650 Hz comfortably, and 8 kHz pulse frequency is enough for 800 Hz. VECTOR will fault or saturate above 650 Hz on most PM240-2 power modules.

4. Ramp Generator Fundamentals

The ramp-function generator (RFG) translates a step change in setpoint into a linear ramp, bounded by acceleration and deceleration limits. The relevant parameters live in the function diagram 3010 / 3020 of the S120 List Manual.

The instantaneous acceleration in rpm/s is therefore:

a = p2000 / p1120   [rpm/s]

For example, a spindle with p2000 = 18 000 rpm and p1120 = 30 s produces 600 rpm/s acceleration. If the gearbox stages cannot tolerate that, raise p1120 (and p1121) until the mechanical transient is within the gearbox's permissible torque.

4.1 Direction change behavior

On VECTOR, the RFG also handles direction reversal. p1120 defines the time to traverse from –n_ref to +n_ref, which means a 0-to-max transition uses half of p1120 if starting from 0. Many integrators are surprised by this. For a true 0-to-rated transition, set:

t_0→max = p1120 / 2

Alternatively, command p2000 to match the working speed rather than the motor's maximum mechanical rating.

5. Extended Ramp Generator with Smoothing

Mechanical systems with backlash, preloaded gear meshes, or weak couplings often oscillate when the ramp corners are sharp. The extended ramp generator rounds the corners of the ramp and can optionally behave as a jerk-limited trajectory planner.

Recommended starter values for a 4-stage gearbox spindle:

• p1120 = 30 s
• p1121 = 30 s
• p1130 = 1.5 s (ramp-up initial rounding)
• p1131 = 1.5 s (ramp-up final rounding)
• p1132 = 1.5 s (ramp-down initial rounding)
• p1133 = 1.5 s (ramp-down final rounding)
• p1134 = 2 (continuous jerk limiting)

Setting p1134 = 2 activates the continuous jerk-limited profile, which is the smoothest of the three profiles and is preferred for high-inertia CNC spindles.

6. Control Word Bits: RFG Enable vs Setpoint Enable

The original problem in the source was caused by driving bit 3 (pulse enable / "speed control enabled input") with what was meant to be the run command. The drive enabled its IGBTs, but bit 6 (setpoint enable) was still 0, so no setpoint reached the speed controller. Symptom: drive shows "RUN" but the motor does not move, and the ramp does not visibly engage.

Resolution: route the 808D spindle enable signal to STW1 bit 6 (setpoint enable) while keeping bits 0, 1, 2, and 3 statically enabled via BICO default wiring. In BICO terms, change p854[0] (source for bit 6 of STW1 in the free function block / digital input matrix) to point to the desired DI of the CU310-2, and verify p850[0] (source for bit 3) remains on the default digital input if used as a hardware enable.

7. Step-by-Step: Configuration in TIA Portal Startdrive

1. Insert the drive. In the TIA Portal device tree, add a SINAMICS S120 CU310-2 PN. Confirm the firmware version is detected correctly (right-click → "Go online" → "Compare").
2. Configure the drive object. In the device configuration, set DO1 to VECTOR (unless the spindle exceeds 650 Hz, in which case choose SERVO).
3. Enter motor data. Open "Motor". Enter the motor's rated voltage, current, power, speed, cos φ from the motor nameplate. Use the motor calculation routine to compute equivalent circuit parameters, or load them from a Siemens motor list (1LE, 1PH, 1FT, etc.).
4. Set the reference speed. Confirm or override p2000. This is the speed that p1120/p1121 reference to.
5. Configure analog input. Open "Setpoints → Analog inputs". For AI0 (default), set the source to p756[0] = 0 (no inversion), scale via p757[0] (0 %), p758[0] (100 %) so that 0 V = 0 rpm and 10 V = p2000. Use r755[0] as the actual input monitor.
6. Wire setpoint source. Set p1000 (main setpoint source) so that the speed setpoint is derived from the analog input. The default for VECTOR is r2050[1] (PROFINET PZD), which is wrong for the standalone analog use case. Change p1000[0] = 2 (analog setpoint) or to a specific BICO source matching your wiring.
7. Configure the ramp-function generator. Open "Function blocks → Ramp-function generator". Enter the values from Section 5.
8. Configure the control word bits. Open "Control / status words" and verify the mapping in Section 6. For standalone analog operation with a hardwired enable from the 808D, keep p850, p851, p852, p854 at their BICO defaults, or assign them to physical DIs of the CU310-2.
9. Set speed limits. p1080 = 0 (minimum), p1082 = rated speed (or max commanded spindle speed) (maximum).
10. Save project and download to drive. Use "Download to device" with the SINAMICS parameter assignment.
11. Run the ramp generator trace. Open "Commissioning → Trace", add the signals r0062 (speed setpoint after RFG), r0063 (speed actual), and r0064 (RFG output). Record a 0→p2000→0 cycle.

8. SINAMICS Starter as an Alternative

Startdrive is sufficient for parameter editing and basic commissioning, but SINAMICS Starter remains the most complete tool for several reasons:

• Faster parameter search across the full list (over 15 000 parameters).
• More detailed function diagrams and trace recording.
• Can run as a standalone offline tool without TIA Portal.
• Better diagnostic view of PROFIdrive telegram traffic.

When the project is in TIA Portal but the trace or expert list is needed, Startdrive can be launched directly with the same SINAMICS project; there is no need to duplicate the configuration. Open the device in TIA, then right-click → "Open with SINAMICS Starter".

9. Web Server Commissioning on CU310-2

The CU310-2 has an integrated web server, accessed by default at http://<drive-IP>/index.html. It is useful for quick verification without installing TIA or Starter.

1. Enable the web server: p8986 = 1.
2. Configure access: p8987 (e.g., write-protect or full read/write).
3. Assign IP address: parameter p8940 (IP), p8941 (subnet), p8942 (gateway).
4. Browse to http://<drive-IP>. The "Diagnostics" tab shows fault memory, the "Parameters" tab allows live write.

10. Verification Checklist

After commissioning, verify each item before handing the spindle to the machine operator:

11. Troubleshooting Matrix

12. Notes on Advancing Torque Pre-Control

The official SINAMICS S120 Function Manual (Entry ID 99472695) describes a method to improve the speed controller's command behavior by computing the accelerating torque from the speed setpoint and feeding it directly to the torque setpoint. This technique is implemented with the pre-control parameter p1496 (acceleration pre-control scaling). For a heavy spindle with frequent direction reversals, enabling acceleration pre-control significantly reduces the speed error during the ramp:

• p1496 = 100 % (default) for full pre-control.
• p0341 (motor moment of inertia) or p0342 (load moment of inertia / total) must be entered accurately, otherwise the pre-control overshoots or undershoots.
• Set p1496 = 0 % if the spindle inertia is unknown or varying (e.g., tool change with different masses).

For the 4-stage gearbox spindle described in the source, where p1120 has been raised to 30 s or more, acceleration pre-control is generally not required, but it is recommended for any ramp time below 10 s with high load inertia.