Configuring Siemens 1PH7 as Generator with Sinamics S120 ALM

1. Overview

The Siemens 1PH7 288-2NF050AA3-Z is a member of the SIMOTICS M family of squirrel-cage induction motors (asynchronous three-phase motors) typically deployed as main spindle or feed drives in machine tools. Although cataloged as a motor, the electromagnetic principle of a three-phase induction machine is fully reversible: when the rotor is driven above synchronous speed by an external mechanical prime mover, the machine becomes an induction generator and delivers real power to its stator terminals. When paired with a Sinamics S120 drive line-up built around an Active Line Module (ALM), the regenerated energy is inverted and fed back into the line supply (grid feedback), so the 1PH7 can be operated continuously as a generator/alternator in industrial test benches, dynamometer stands, kinetic energy recovery systems, and hydro/wind micro-generation packages.

This reference walks through the system identification, control architecture, software commissioning with STARTER, parameterization for generator/regenerative operation, and verification checks for the following equipment stack:

• 1PH7 288-2NF050AA3-Z induction motor (frame size 288, forced-ventilated)
• 6SL3300-7TE35-0AA0 Active Interface Module (AIM)
• 6SL3335-7TE35-0AA0 Active Line Module (ALM)
• 6SL3325-1TE36-1AA0 Sinamics S120 Motor Module (booksize/chassis variant)
• CU320-2 Control Unit (implicit to the S120 line-up)

All commissioning steps assume STARTER V5.x or the TIA Portal equivalent SINAMICS Startdrive, communicating with the drive over PROFIBUS, PROFINET, or Ethernet service interface.

2. Decoding the 1PH7 288-2NF050AA3-Z Part Number

The Siemens SIMOTICS M type designation follows a structured code. Confirm the exact data on the motor rating plate against the order documents before relying on any inferred value.

3. Drive Line-up Topology

The Sinamics S120 is a modular drive system. The line-up recommended for a high-power 1PH7 (frame 288 typically corresponds to >100 kW continuous) is the Chassis format with an active front end, because chassis Active Line Modules are bidirectional and can return energy to the line. The interconnection is:

3-phase line supply → line reactor (typically integrated in AIM) → Active Interface Module 6SL3300-7TE35-0AA0 (LC filtering, pre-charge, voltage sensing) → DC link → Active Line Module 6SL3335-7TE35-0AA0 (IGBT inverter, line-side) → shared DC bus → Motor Module 6SL3325-1TE36-1AA0 (motor-side inverter) → 1PH7 motor stator.

The Active Line Module is the key component that enables regeneration. Unlike a Basic Line Module (diode rectifier) or Smart Line Module (transistor rectifier with brake chopper only), the ALM uses IGBTs in an active front-end topology and a clean-up filter (AIM) to draw nearly sinusoidal current and to allow bidirectional power flow. When the DC link voltage rises above the rectified line peak (controlled threshold, typically around 1.5-1.6 × V_line,LL,RMS), the ALM transitions seamlessly into inverter mode and exports the surplus energy to the grid.

The Motor Module 6SL3325-1TE36-1AA0 in the user's stack is sized for high motor current. In motoring mode it converts DC to variable-frequency, variable-voltage AC for the stator. In generator mode the same inverter operates as a synchronous rectifier, converting the stator's variable-frequency, variable-voltage AC into DC for the DC link. The ALM then ships that energy to the line.

4. Generator Mode Operating Principle

An induction machine delivers mechanical power P_mech = T · ω_m when the rotor turns faster than the synchronous speed set by the stator frequency. The slip s = (n_s - n_m) / n_s becomes negative, the air-gap torque reverses, and energy flows from the shaft to the stator. The Sinamics S120 uses field-oriented control (vector control) to maintain a defined flux in the machine even when the rotor is being driven by an external load, so the same control structure used for high-dynamic spindle operation also works for generator operation.

Three conditions must be satisfied:

1. The stator must be excited with controllable voltage/frequency (the Motor Module does this).
2. External mechanical energy must drive the shaft above synchronous speed (a prime mover - turbine, engine, flywheel, dynamometer motor - is required).
3. The DC link must accept the energy and the ALM must feed it back to a stiff, in-tolerance line supply.

If the line is lost or distorted, the ALM will inhibit regen and the DC link will rise. The drive's integrated braking chopper (if equipped) or an external brake resistor will clamp the DC bus, and the drive will trip with F30002 (DC link overvoltage) or F07900 (Line failure detected by ALM) as a safety response.

5. Prerequisites

Before recommissioning the stack in generating mode, verify the following:

6. Software: STARTER Setup

STARTER (Startdrive commissioning tool) is the recommended commissioning suite for legacy Sinamics S120 systems and is still distributed free of charge. The official entry point is the SIOS article STARTER commissioning tool download and overview (SIOS 26233208). Newer TIA Portal users can also commission the S120 with SINAMICS Startdrive, but the parameter numbers are identical.

General commissioning flow inside STARTER:

1. Create a new project: Project → New → Create new project, give it a meaningful name, and insert the drive unit at the correct topology level.
2. Set the PG/PC interface: Options → Set PG/PC interface. Select the Ethernet adapter bound to the S120 service access (default IP 169.254.11.22 on the CU320-2 X120, or the PROFINET name configured for the project).
3. Connect online: highlight the drive and click Connect to target system. Use Accessible nodes if the IP is unknown.
4. Automatic configuration: in the configuration tree, right-click the drive and choose Automatic configuration. STARTER will read out the topology from the DRIVE-CLiQ ports, identify the AIM, ALM, Motor Module, and encoder, and populate the device list.
5. Motor identification: enter the motor data from the 1PH7 nameplate (rated voltage, current, power, power factor, speed, torque) into the motor wizard. The values flow into parameters p0304, p0305, p0307, p0308, p0310, p0311, p0314, p0335.
6. Encoder selection: confirm the encoder type matches what STARTER autodetected. Adjust p0400 family if a non-DRIVE-CLiQ encoder is wired through an SMC.
7. Control mode: choose vector control with speed controller (p1300 = 21) for the most stable generator behavior. Sensorless vector control (p1300 = 22) can be used above a minimum speed (typically 10-20 % of rated) if encoder feedback is unavailable, but for a grid-tied generator operation with a stiff prime mover, encoder-based vector control is preferred.
8. Download: Target system → Load to target device (with copy RAM to ROM) to push the project to the CU320-2.

7. Step-by-Step Commissioning in Generator Mode

Use the S120 List Manual and the S120 Function Manual as the authoritative reference. The full manuals are linked at the end of this article. The procedure below assumes the project is online and the topology has been read out successfully.

1. Power up the line, then the 24 V Control Unit supply. The CU320-2 boots and the AIM/ALM pre-charge the DC link. Wait for the "Ready" LED on the ALM.
2. Run motor data identification (motoring): p1910 = 1, then issue ON to spin the shaft. The drive measures stator resistance, leakage reactance, and magnetizing curve. Wait for the routine to complete, then acknowledge any F0793x alarm.
3. Run rotating measurement: p1960 = 1, then ON. The drive accelerates to a set speed, measures the moment of inertia and friction, and updates p1115, p1121, p0341, p0342. Allow the routine to finish without external torque disturbance.
4. Configure the speed controller: p1460 (Kp_n) and p1470 (Tn_n) can be left at the STARTER autotuning default; tighten only if the generator shows sustained oscillation when the prime mover applies step changes in torque.
5. Configure the torque limits: p1520 = +rated motor torque, p1521 = -rated motor torque. Set p1530 (motoring power limit) and p1531 (regenerative power limit) to the rated motor power (p0307). For generator-only operation, increase p1531 up to the value the mechanical system can absorb at overspeed, but do not exceed the Motor Module's rated I (p0205).
6. Enable ramp-function generator: p1120 (ramp-up) and p1121 (ramp-down) should be configured for the prime mover's safe acceleration. A slow ramp prevents inrush at the moment the line is paralleled.
7. Configure the signal sources for control words: in generator mode the speed setpoint typically comes from a fixed value (p1001, p1002, ...) or from a higher-level controller. Wire the source to p1070 (main setpoint) and the ON/OFF1 commands per your PLC/control strategy.
8. Decide on droop / grid-parallel vs. island: for true grid-parallel operation with closed-loop active and reactive power control, you must use the ALM's Line droop (p5401) and active power controller (p5402) and a separate synchronization check. The S120 ALM is normally a line-follower (it locks to the grid); it does not black-start. For islanded generator operation an upstream controller (e.g. SIMATIC S7 with SINAMICS blocks) regulates the setpoint.
9. Save the project: Target system → Copy RAM to ROM, then back up the project file on the engineering station and on a CF card inserted in the CU320-2 (if used).
10. First run in generator mode: with the prime mover at rest, give the drive ON. Bring the prime mover up to rated speed slowly. Watch the ALM display: the line-side power readout (r0032, r0080) should swing negative as soon as the rotor exceeds synchronous speed. Check r0046.29 (ALM in regen) and r0082.3 (line feed-in active) in STARTER's trace.

8. Key Parameters for Generator Operation

The numbers below are the S120 standard indexing. Always cross-check with the active firmware version's List Manual, because parameter numbers and ranges change between firmware releases. The values shown are conservative defaults; actual commissioning must use the project's real motor data.

9. Active Line Module - Line-Side Configuration

Because the regenerated energy is exported through the ALM, the line-side parameterization is as important as the motor-side parameterization.

• Line voltage (p0210): enter the actual line-to-line RMS voltage at the AIM terminals, not the nominal grid voltage. Voltages of 380 V, 400 V, 415 V, 440 V, 460 V, and 480 V are common and each shifts the DC link setpoint.
• Line frequency (p0211): 50 Hz or 60 Hz, with the appropriate PLL bandwidth (p3400).
• Pre-charge and line monitoring: keep p0278 (line monitoring time) at the default 2 s. The ALM performs a phase, voltage, and frequency check on every line connection; if the check fails the drive trips with F07900/F07901.
• DC link setpoint: p3510 controls the ALM's DC voltage target. The default is derived from p0210 and is typically 1.5 × V_line,LL,peak / √2. Do not reduce it below the motor's rectified EMF at maximum speed, or the Motor Module will pull the DC link down and stall in regen.
• Reactive power / cosφ: by default the ALM is set to cosφ = 1 (no reactive current). For grid code compliance, adjust p5420 (reactive current setpoint) and configure the droop characteristic (p5421) per the utility requirements.

10. Encoder, SMC, and Speed Feedback

The 1PH7 288-2NF050AA3-Z typically ships with a DRIVE-CLiQ encoder (e.g. AM22DQN) connected through a Sensor Module. Verify the Sensor Module's DRIVE-CLiQ port lights up green. If the drive reports F3x051 (encoder fault), check the DRIVE-CLiQ cable for damage and confirm p0430, p0431, and p0432 (encoder word/bit configuration) match the encoder data sheet. After replacing an encoder, always re-run p0440 = 1 (accept encoder) and p1990 = 1 (encoder tuning) so the commutation offset is relearned.

11. Cooling and Thermal Limits

The 1PH7 288 has a frame-size thermal envelope that the drive monitors via KTY84/PTC inputs wired through a Terminal Module (TM31/TM120). The Motor Module's I2t model (p0290-p0299) and the motor's thermal model (p0610-p0613) must both be enabled to protect against:

• Sustained regen at low speed (poor self-ventilation on the 1PH7 with separate fan only - the fan is independent of rotor speed).
• Repeated overcurrent transients during grid faults (the ALM will momentarily block regen, raising DC link and forcing the motor into field-weakening; this can overheat the rotor).

Configure the overtemperature responses (p0610 = 1 = warning + fault) and verify with the trace tool that the motor temperature model stays below 100 % during a full power regen cycle.

12. Verification and Acceptance Test

Use the STARTER trace recorder to capture the following quantities during a controlled no-load regen ramp:

1. r0021 (motor speed) - should track the setpoint with no oscillation.
2. r0027 (output current amplitude) - should be smooth, no DC offset.
3. r0030 (torque actual) - should be slightly negative (generator torque).
4. r0032 / r0080 (active power) - should go negative when the prime mover crosses synchronous speed.
5. r0082 (ALM status word) - bit 3 (line feed-in) should set.
6. ZSW1 (status word 1) from the Motor Module - bit 14 (regen active in vector control) should set.

Acceptance criteria:

13. Troubleshooting Matrix

14. Safety and Grid-Code Notes

Using a 1PH7 plus Sinamics S120 ALM as a grid-tied generator falls under the same local grid code (e.g. VDE-AR-N 4105 in Germany, IEEE 1547 in the US, AS/NZS 4777 in Australia/New Zealand) as any other inverter-based generation. Typical requirements include:

• Anti-islanding detection (the ALM implements passive methods but may need an external RoCoF relay).
• Frequency-dependent active power reduction (P(f) curve).
• Voltage-dependent reactive power (Q(U) curve).
• LVRT/HVRT behavior during grid faults.

Verify the project-specific protection settings with the local utility operator before energizing. The S120 supports many of these features through the ALM's free-function blocks, but the engineering effort is not trivial.

15. References for Further Reading

Authoritative Siemens documentation for this stack:

• SINAMICS S120 Function Manual (SIOS 109754313)
• STARTER commissioning tool (SIOS 26233208)