Sinamics S120 Testmodel1 Commissioning Resolving Switch-On

Problem Description

The SINAMICS S120 Testmodel1 is a portable demonstration suitcase used by Siemens for field training, trade-show demos, and customer workshops. It is a complete, single-axle (or two-axle) drive line-up on wheels that lets engineers run real motion profiles (rotary cutter, flying saw, cross-cutter) without a full cabinet. The standard configuration in the demo unit comprises:

• One Control Unit (typically a CU320-2 DP or CU320-2 PN that hosts the closed-loop drive control and the communications master).
• One Smart Line Module (SLM), 5 kW or 10 kW class, with an Active Line Module filter set; the SLM provides a regulated, regenerative DC link without drawing reactive power from the line.
• One Double Motor Module (two-axis inverter) feeding two servo motors.
• One Operator Box 6AG1064-1AA01-0AA0 – a Siemens AG-specific (SIPLUS / ruggedised) handheld keypad for first commissioning.
• Optionally a SIMOTION D425 controller that runs the demo technology programs (rotary cutter, flying saw, etc.).

When the unit is recovered to factory defaults and put through the automatic first commissioning wizard in SINAMICS Starter (or TIA Portal with Startdrive), the drive is configured for servo control, the topology is found online, and the user changes a handful of parameters and tries to spin the motor from the control panel. The motor does not turn. The diagnostic buffer reports one of the following:

• Fault F7900 / Alarm A7900 – "Drive: switch-on inhibit active" (also worded as "the switch-on disable of the drive is active" in Starter / Startdrive plain text).
• Status word r0002 showing 0011 (c0002 = commissioning mode active, switch-on inhibit set).

Pressing the green 1 button on the Operator Box (ON / OFF1) does not start the drive. The control panel reports a missing enable even though the panel "assume control priority" command has been issued.

Root Cause Analysis

The S120 in the Testmodel1 sits in the drive state c0002 = "Commissioning", which is one of the persistent switch-on-inhibit conditions listed in the SINAMICS S120 Function Manual (FH1). For the drive to leave this state and accept the ON command, three independent enable paths must all be high:

1. Software enable – p0840 = 1 (ON/OFF1 from the active command source) and p0864 = 1 (line contactor / line operation request from the Smart Line Module).
2. Commissioning filter released – p0010 = 0. The drive filters write access and keeps the switch-on inhibit active while p0010 ≠ 0. The "first commissioning" wizard leaves p0010 in a non-zero value until the user explicitly closes the wizard with Finish.
3. Hardware enable – EP (Enable Pulses) at the digital input connector on top of the Control Unit. This is the most common cause on the Testmodel1: pin 3 of the small grey connector is not tied to +24 V and pin 4 is not tied to 0 V, so the drive parks itself in STO (Safe Torque Off) and reports switch-on inhibit.

Per the S120 Function Manual (FH1, section "Enable signals / Enable logic"), the EP terminal is the hardware gate in front of the IGBT firing pulses. With EP low, the inverter is safely torque-free regardless of what the controller requests, and the ON command is rejected with the switch-on inhibit message.

Pinout of the EP Connector

The EP (Enable Pulses) terminals live on the small grey 24 V spring-cage connector that plugs into the top of the Control Unit, normally marked X21 / X22 depending on the Control Unit variant. On the Testmodel1 (CU320-2) the relevant pins are:

Measure between pins 3 and 4 with a multimeter before going online. The reading must be ≥ 18 V DC under load (typical 22–26 V DC from a SITOP or the unit's internal 24 V rail). Reverse polarity will not damage the input but will hold the drive in STO. Open circuit (jumper removed) will also hold STO.

Pre-Checks Before Re-Commissioning

1. Confirm the line voltage that the suitcase is plugged into. The Testmodel1 is shipped for 400 V class by default. The default p0210 is 600 V (the universal factory default), which causes the Line Module to refuse pre-charging and to keep the drive in switch-on inhibit. Set p0210 to the actual line-to-line RMS voltage (e.g., 400 V for 400 V L-L, 480 V for 480 V L-L).
2. Verify the DRIVE-CLiQ connections between the Control Unit, the Smart Line Module, and the Double Motor Module. The diagnostic buffer should report a clean CU_x > SLM > DMM_x topology with no F0135 / F08501 errors.
3. Check the 24 V logic supply LED on the Control Unit. Green = OK. Off or red = EP, the encoders, and the DRIVE-CLiQ ports are all dark.
4. Open the Operator Box 6AG1064-1AA01-0AA0 cable to the Control Unit. Pin 5 / pin 6 of this cable carry the parallel I/O that map onto the drive's p0840 / p0844 / p0852 sources.

Step-by-Step Commissioning Procedure

The following sequence is the verified commissioning flow for the Testmodel1 on a 400 V supply with a SIMOTION D425 in the loop. It assumes Starter V5.x (or Startdrive in TIA V18+) and the unit is connected via Ethernet (PN) or PROFIBUS.

1. Reset to factory defaults. In the project tree, right-click the drive object → Drive object > Restore factory settings. Confirm the prompt. The unit will reboot and clear all parameters including the password.
2. Go online and find the target device. Click Project > Find target devices… (Starter) or Online > Accessible nodes (TIA). The Control Unit plus the Smart Line Module and the Double Motor Module should appear as one DO each.
3. Run automatic drive configuration. Double-click the drive object → Configuration > Automatic drive configuration. Accept the status "First commissioning". Choose Servo as the control mode, leave the wizard in Online mode, and click Load to PG. Starter will detect the connected motors from the electronic rating plate and create a usable configuration.
4. Release the drive-object-level switching-in. Set p0864 (line operation request) from 0 to 1 and Copy RAM to ROM. This tells the Smart Line Module that the infeed is allowed to close its line contactor and pre-charge the DC link.
5. Set the device supply voltage. Change p0210 from the factory default of 600 V to the actual line-to-line voltage. For a 400 V European supply use p0210 = 400. For 480 V North America use p0210 = 480. Copy RAM to ROM and power-cycle the unit so the Line Module re-initialises with the correct under-voltage / over-voltage limits.
6. Wire the ON command. In the demo unit the ON/OFF1 command source is the Operator Box. Set p0840[0] = r2090.0 (PROFIdrive control word bit 0 from the SIMOTION) or p0840[0] = 722.0 (digital input DI 0 of the CU320-2 terminal block) depending on whether the D425 or the handheld box is the master. Change the value from 0 to 1 only after you have confirmed the command source with the active BICO interconnection list (BICO must be in the order: interconnect first, then enable).
7. Close the first-commissioning wizard. This sets p0010 = 0. If you skip this step, the drive stays in Commissioning mode and rejects every ON command. Verify with r0002 – it must read 0000 0000 (drive ready) once the DC link is pre-charged.
8. Energise the EP terminal. Apply +24 V between pins 3 and 4 of the grey connector on top of the Control Unit. The drive should leave the STO active state; the diagnostic buffer entry STO selected via terminal will be cleared within 200 ms.
9. Take control from the panel. Open Control panel > Assume control priority. Accept the warning dialog. Setpoint n = 1000 rpm. Click Enable.
10. Press the green ON button (1) on the Operator Box. The motor must accelerate to 1000 rpm. If it does not, refer to the fault matrix in the next section.

Parameter Reference

Diagnostic Word r0046 – Missing Enables

When the drive refuses to start, the fastest way to identify which enable is missing is to read r0046 (missing enables). Each bit has a fixed cause:

For the Testmodel1, if you see only bit 4 set, the problem is purely on the EP terminal. If bit 3 is also set, the Smart Line Module is unhappy – re-check p0210 and the three-phase line voltage. If bits 0 and 4 are set, the BICO source for p0840 is wrong and the EP terminal is also open.

Firmware and Compatibility Notes

• The Testmodel1 Control Unit ships with SINAMICS firmware V5.x (typically V5.2 SP3 or V5.3 at delivery). The same procedure applies to V4.8 / V5.1 with one difference: p0010 must be set to 0 manually because older firmware does not auto-reset on wizard close.
• Starter V5.5 (and later) and Startdrive in TIA V18 are compatible. Startdrive V17 has a known issue where the Finish button on the commissioning wizard does not write p0010 = 0 back to the drive. Workaround: manually set p0010 = 0 in the parameter table before the first ON attempt.
• The Operator Box 6AG1064-1AA01-0AA0 is a SIPLUS variant (conformal coating) of the standard 6AG1064-1AA00-0AA0 box. It is functionally identical. The 6AG1 prefix indicates it is rated for harsher environments and does not change the firmware behaviour.
• If the unit is upgraded to include an Active Line Module (ALM) instead of the Smart Line Module (SLM), set p0210 to the line L-L voltage plus a tolerance of 10 %. ALM has tighter DC-link voltage regulation and will pre-charge but stay in switch-on inhibit if p0210 is mis-set by more than ±10 %.

Verification

1. Read r0002 – all bits in byte 0 should read 0 (drive ready).
2. Read r0046 – must equal 0 (no missing enables).
3. Open the control panel, assume control priority, set a setpoint of 500 rpm, click Enable, and press the green ON button. The motor must accelerate to 500 rpm with no new fault or alarm entries in the diagnostic buffer.
4. Check the Smart Line Module DC-link voltage with the Trace function: it should sit at 600 V (for 400 V L-L) or 720 V (for 480 V L-L) ±2 %. The Double Motor Module should report the same voltage on r0070.
5. Stop the drive with the red OFF button. The motor must ramp down on the configured deceleration (default 2 s on the Testmodel1). r0002 should return to Ready with no fault entries.

Troubleshooting Matrix

FAQ