Diagnosing F30001 F30003 F30004 Faults on SINAMICS G120

Problem Overview and Field Manifestation

A population of SINAMICS G120 drives, most built around the 6SL3210-1KE15-8AF2 PM240-2 Power Module, is used to start a 440 V conveyor section. Each drive is configured through the EXPERT commissioning path with the Parallel Connection of Motors (multi-motor / "Mehrere Motoren") function block active, and each drive feeds between one and eleven 200 W 440 V induction motors wired in parallel over approximately 100 m of motor cable. The drive raises no fault when one to four motors are running, but trips the moment five or more motors are energized simultaneously — even with no mechanical load coupled and with the motor-identification run completed. The trip family is consistent:

• F30001 — Power unit overcurrent
• F30003 — DC-link undervoltage
• F30004 — Inverter (heat-sink) overtemperature

All three faults arrive together when more than four motors are requested to start, and the on-load timer (p1120 / p1130-related ramp / on-time) is set as low as 1 s, which is short enough that the drives are clearly tripping on inrush or capacitive charging, not on a slow thermal excursion.

6SL3210-1KE15-8AF2 Rating vs Parallel Motor Load

The 6SL3210-1KE15-8AF2 is the SINAMICS G120 PM240-2, frame size FSA, 400 V class, rated 1.5 kW at High Overload (HO) (Light Overload / LO: 1.5 kW continuous, HO: 1.1 kW continuous, 150 % for 60 s, 200 % for 3 s). Its typical output current at 400 V 3-phase is in the order of 3.0 A LO / 2.6 A HO, depending on firmware. The reference manual for the PM240-2 is SINAMICS G120 PM240-2 Power Modules manual (109751361).

The parallel load demands a totally different calculation:

Fault Code Reference (SINAMICS G120 / G120C)

Each fault class points to a different physical mechanism. Treat the three as a single symptom cluster:

The exact code list and reaction defaults are in the SINAMICS G120/S120 List Manual (109751360). The interaction above (overcurrent → DC-link collapse → thermal rise) is the typical signature when the drive is asked to charge too much external capacitance (motor cable) and too many motor magnetising branches at once.

Root Cause 1 — Motor Cable Capacitive Loading

A 4-core motor cable of ≈ 100 m typical PVC-insulated, 1.5 mm² has a phase-to-ground capacitance of about 0.2–0.3 µF per phase. With eleven motors, the parallel capacitance seen by the drive is:

• Per-phase cable + motor leakage: ≈ 11 × 0.25 µF ≈ 2.75 µF
• Charge stored at 540 V DC bus peak: Q = C·V ≈ 1.5 mC
• In-rush peak if all this capacitance is charged in 100 µs: I_peak = C·dV/dt ≈ 14 A

The PM240-2 FSA IGBTs are specified for short-circuit currents in the tens of amps but only for a few microseconds. A 100 µs / 14 A burst from cable charging will trip F30001 reliably on the second or third simultaneous motor. This is also why the trip count rises with motor count, not with mechanical load.

Mitigation options, in order of cost and effectiveness:

1. Use a sine-wave output filter (e.g., SINAMICS G120 PM240-2 accessories chapter) — limits dV/dt, suppresses the capacitive charging current at the terminals.
2. Install an output reactor sized for frame A (≈ 1.6 mH / 5 A line current) to damp the charging current. The candidate part number referenced in the field case is 6SL3203-0CE21-0AA0; because the same article number family covers both line filters and output reactors, cross-check the printed product label against the SINAMICS G120 catalog entry before ordering.
3. Reduce PWM switching frequency (p1800) to 2 kHz to lower the per-cycle dV/dt charging impulse.
4. Spread motor starts (already partly done with the 1 s on-load time, but the ramp itself is the problem).

Root Cause 2 — PWM Switching Frequency and Harmonic Current

The default p1800 PWM frequency for a PM240-2 FSA is 4 kHz (range 2–16 kHz). At 4 kHz the cable charging occurs every 250 µs; the cumulative energy dumped into the cable capacitance is roughly proportional to the switching frequency. The loss path is:

P_cable ≈ C_cable · V²_DC · f_pwm

For 2.75 µF, 540 V and 4 kHz: P_cable ≈ 3.2 W continuous, but the dI/dt impulses dominate the trip. Halving the switching frequency halves the charge-per-second, and the IGBT thermal stress (heat sink) drops roughly proportionally — which is why the same change also clears F30004.

For this 11-motor / 100 m cable topology, set p1800 = 2 kHz as the first corrective action. Document the change in the parameter print-out and re-rate any other drive that shares the cable type to the same value to keep the fleet behaviour identical.

Root Cause 3 — Parallel Motor Model and Current Sharing

The EXPERT commissioning path with the parallel connection function still expects to be told about one equivalent motor whose rating matches the combined load. The relevant parameters and the values the field case requires:

The combined motor current at 440 V (verify which connection the field used — 3-phase or single-phase, RMS line current):

• If 440 V is the line-to-line voltage and the motors are 3-phase: I = (11 · 200) / (√3 · 440 · η · pf) ≈ 5.3 A at η · pf = 0.55.
• If 440 V is the single-phase voltage applied to each motor: I = 11 · (200 / (440 · η · pf)) ≈ 9.1 A.

Enter whichever figure matches the as-built wiring. The drive will then build its thermal model around a single virtual motor of the combined rating. The internal I²t model no longer protects the individual 200 W motors. That protection must be installed externally (see below).

Parameter Corrections Summary

Apply the following parameter changes on every 6SL3210-1KE15-8AF2 that feeds the parallel group. Use STARTER or SINAMICS Startdrive in TIA Portal:

1. p1800 = 2 (PWM frequency, kHz).
2. p0290 = 0 (do not reduce output frequency on thermal warning) or set the response strategy as appropriate for the line-up.
3. p1240 = 1 (Vdc controller enabled) — keeps the DC link inside the F30003 window.
4. Combined-motor rating per the table above (p0304, p0305, p0307, p0308).
5. Re-run motor identification with p1900 = 2 (still-data identification) on the combined motor. The motor-data identification of eleven parallel 200 W motors gives a very different equivalent circuit than one 2.2 kW motor; accept the result only if the drive does not exit with F07953 (motor data identification fault).
6. p1120 (ramp-up) ≥ 3 s to limit inrush at every simultaneous start; 1 s as currently set is too aggressive for this topology.

Save with RAM → ROM (p0971 = 1) and back up the project to the MMC card.

Output Reactor vs Line Filter vs Sine Filter

Three accessory classes are often confused in the field. Apply them based on what you actually need:

Per-Motor Thermal Overload is Mandatory

When the SINAMICS G120 internal I²t model is told there is one motor of 2.2 kW, it can no longer distinguish whether one of the eleven 200 W motors is mechanically jammed. Every individual motor must therefore have its own thermal overload:

• Thermal overload relay (e.g., Siemens SIRIUS 3RB20 / 3RB30) sized to roughly 1.0–1.1 A at 440 V (verify against actual motor FLC).
• Or PTC thermistor wired to the drive's motor-temperature input (X2.13 / X2.14 on the Control Unit) with p0601 = 1 and p0604 = 10 °K for the warning threshold.

Add a suitably rated short-circuit protective device (motor-protective circuit breaker) per branch as well; the drive alone does not satisfy IEC 60204-1 single-fault protection for paralleled motors.

Commissioning Procedure for Parallel Motor Groups

1. Power down, lock out, verify zero potential on the DC bus (wait 5 min after disconnection).
2. Install output reactor between drive U2/V2/W2 and the motor junction box. Torque the power terminals to the value printed on the drive (≈ 2.5 Nm for FSA).
3. Verify motor-cable shield bonding at the drive end only (high-frequency bonding at both ends via 100 nF capacitors if the run exceeds 25 m).
4. Set p1800 = 2, p1120 = 3 s, p1130 = 1 s, p1131 = 1 s.
5. Enter combined motor data per the parameter table above.
6. Run static motor-data identification: p1900 = 2, give run command, wait for completion or F07953.
7. Start one motor only (isolate the other ten). Verify rotation, current, slip.
8. Add motors one at a time until the full group runs. Read out r0027 (current utilization) and r0037 (heatsink temperature) at each step.
9. With all eleven motors running at no-load for 15 min, verify: r0027 ≤ 95 %, r0037 ≤ 70 °C, no warnings, no faults.
10. If the drive is still tripping, the inverter frame size is the limiting factor. Either split the eleven motors onto two drives of ≥ 3 kW (e.g., 6SL3210-1NE21-8UL0 / 6SL3210-1PE23-3UL0 for PM240-2) or replace each 6SL3210-1KE15-8AF2 with a 2.2 kW or larger PM240-2 unit.

Verification and Acceptance Criteria

Field-Proven Caveats

• The 440 V specification is within the 380–480 V G120 range, but at 440 V the drive's Vdc-max threshold and braking-chopper activation adjust slightly. Do not lower p1240 below the default unless measurements justify it.
• The "PARALLEL" EXPERT function is essentially the multi-motor V/f feature. It is not designed for high-performance or vector-controlled parallel motors — it assumes linear V/f, low dynamic load, and a single thermal model.
• Eleven motors on one drive is the upper practical limit for a 1.5 kW PM240-2; beyond that the I²t balancing and thermal protection lose meaning. The recommended architecture is to use a single drive + several mechanically coupled motors through one gearbox, or to use one drive per motor (or per small group of two to four motors) sized so that the per-drive load is ≤ 70 % of its continuous rating.
• 440 V motors with 200 W nameplate are very small. Their locked-rotor current can exceed 5 × FLC; this is what kills the drive during the first cycles of multi-motor energization. A soft-start voltage ramp on the parallel group with p1310 (voltage boost) reduced to 50 % of default mitigates this.
• If the conveyor is regenerative or has any overhauling load, install a braking resistor sized for the new PM240-2 — the FSA frame is the smallest PM240-2 and only accepts specific braking resistors.
• Re-check p0290 (load generator response to overtemperature). Setting it to "Reduce motor speed" may avoid trips but masks the underlying thermal overload.

Quick Diagnostic Matrix

Recommended Replacement Strategy

Because the 6SL3210-1KE15-8AF2 (1.5 kW FSA) is materially undersized for eleven 200 W motors at 100 m, the engineering recommendation is one of the following — in order of preference:

1. Replace each 1.5 kW FSA with a 2.2 kW or 3.0 kW PM240-2 (e.g., 6SL3210-1NE21-8UL0 or 6SL3210-1PE23-3UL0) and apply the parameter changes above. This keeps the multi-motor topology, but provides the necessary continuous current and thermal headroom.
2. Split each parallel group into two sub-groups, with each sub-group on its own properly sized drive. This also gives you motor-isolated fault propagation — one fault no longer stops the whole conveyor.
3. Use a larger central drive (e.g., PM240-2 FSB or FSC at 5.5 kW) feeding the eleven motors through a sine-wave filter. Highest reliability, but the highest cost.

Options 1 and 2 keep the existing control architecture and minimise wiring changes. Whichever option is chosen, apply the parameter changes listed above, install the per-motor thermal overload, and complete the verification matrix before releasing the conveyor back to production.