450 A / 13 kW Regen — Gen7 Size 2

This report continues the Gen7 size 2 high-current regen series that started with OV-TEST-HW-REGEN-400A-GEN7-SIZE2, using the same bench: Sorensen supply (regenerative sink limited to ~50 A) with a Chroma DC electronic load bank in constant-voltage mode at 150 V across the DC link. The machine was spun faster this time — approximately 2,000 RPM shaft speed versus ~1,470 RPM in the 400 A run — so each amp of q-axis current returned more power. After a rapid staircase the inverter held a 450 A q-axis command for 77.7 s, returning 12.8 kW on average (13.4 kW peak) to the DC link, until the inverter overtemperature protection tripped at ~80 °C baseplate partway through the commanded stop. The trip matches the intended protection behavior documented in OV-TEST-HW-THERMAL-OTP-200A-GEN7-SIZE2.

This run also closes the open item from the 400 A report: the phase-current "spikes" seen on the oscilloscope there were the Tektronix current clamps saturating — they are rated at 150 A, not the 400–450 A being measured — a measurement artifact, not an inverter anomaly.

Test setup

• DUT: OpenVVVF Gen7 size 2 inverter hardware, firmware foc_demo graph (hash 855dbcee90d611cb, same build as the 400 A run).
• Machine: Induction machine coupled to a Sierra CP Engineering dynamometer at approximately −2,000 RPM mechanical during the staircase and hold.
• DC supply: Sorensen bench supply (regenerative sink limited to ~50 A) in parallel with a Chroma DC electronic load bank in constant-voltage mode at 150 V across the DC link. The supply held ~145 V on the bus at low regen current, so the Chroma clamp engaged from roughly the 300 A step onward.
• Instrumentation: RTE Studio telemetry (all quoted currents and powers are inverter telemetry, not the clamp channel). No bench photographs were taken this session; bench and instrument photos from the identical setup are in the 400 A report.
• Temperature channels: baseplate NTCs TS1 (temp_inv1_c) and TS2 (temp_inv2_c); TS3 (temp_inv3_c) was not enabled (wiring defect, unrelated to the test).

Test conditions

Procedure

1. Pre-charged and enabled the inverter; the dynamometer held the coupled machine at ~2,000 RPM.
2. Stepped IqVar 25 → 200 A, then 300/400/450 A with short dwells. The bus rode the ~145 V supply until regen exceeded its sink capability, then the Chroma clamp held 150 V from ~300 A onward.
3. Held the 450 A command while logging telemetry and watching the baseplate NTCs. TS1 rose at ~0.6 °C/s through the hold.
4. With TS1 at ~79.5 °C, commanded IqVar 0. Temperature continued rising through the slew-limited decay, and the overtemperature protection tripped ~2.3 s into the stop at TS1 = 80.1 °C, cutting the current immediately. Telemetry continued through the ~2-minute cooldown.

Electrical results

Per-command statistics from the full-rate telemetry log (Pdc = DC-link power, Idc = DC-link current). Short segments average below their command because the slew-limited ramp occupies most of the window:

At 2,000 RPM the back-EMF is higher than in the 400 A run, so the same 150 V clamp accepted ~85 A of DC-link current instead of ~56 A — that is where the 13 kW came from. Current control remained clean throughout: cg_vlimit_scale = 1.000 for the entire session (all clamping external), raw and filtered Iq tracked, and no gate faults occurred. The only fault was the overtemperature trip itself.

• Machine-terminal power (calculated): from the logged dq quantities (peak-amplitude convention, P = (3/2)(vd·id + vq·iq), Q = (3/2)(vq·id − vd·iq)), the machine delivered 13.41 kW mean during the hold while drawing ≈7.2 kvar of magnetizing reactive power (quoted as magnitude) — 15.23 kVA, power factor ≈ 0.881. The 0.61 kW between machine output and the 12.80 kW reaching the DC link is the inverter's own dissipation — calculated inverter efficiency ≈ 95% — which is exactly what drove the dry-mounted baseplate to the 80 °C trip in 78 s.

Thermal results and OT trip

Baseplate temperatures rose steeply under 13 kW with no thermal interface work (the assembly was still the dry-mounted setup of the previous sessions):

• Baseplate TS1 (temp_inv1_c): 30.6 °C at the start of the staircase, 33.2 °C when the 450 A command was issued, 80.1 °C at the fault transition — a ~0.58 °C/s rise through the hold. Post-trip peak 81.2 °C at t ≈ 168 s (thermal lag).
• Baseplate TS2 (temp_inv2_c): 33.4 °C at start, 75.5 °C at the trip; post-trip peak 76.5 °C.
• The controller entered FAULT with flags 0x04000000 (OvertemperatureInverter) at t = 164.33 s, 79.8 s after the 450 A command and ~2.3 s after the stop command. This is the same flag and threshold region as the 200 A OTP demonstration (trip at 80.0 °C logged), i.e. intended protective behavior rather than a malfunction.
• After the trip the gates disabled immediately (no slew — the fault path cuts current at once) and both channels cooled to ~49–51 °C by the end of logging.

Resolution of the 400 A current-spike observation

The 400 A report closed with an unexplained oscilloscope observation: narrow repetitive spikes on the phase-current traces during the 400 A holds. The cause is now identified as measurement artifact — the Tektronix current clamps are rated at 150 A and clipped/saturated at the 400 A phase currents, distorting the traces. The inverter's own telemetry in that run showed no anomaly, which is consistent with this conclusion. The spikes should not be treated as a hardware finding; no further investigation of the inverter is required on that count.

Telemetry overview

Open full session: View the run in the Telemetry Viewer

Observations

• Raising shaft speed to 2,000 RPM lifted regen power at the same 150 V clamp from 8.8 kW (400 A run) to 13 kW — DC-link current scales with available mechanical power, not with the clamp voltage alone.
• The Chroma clamp plus ~145 V supply setpoint meant the clamp engaged from ~300 A onward, earlier in the staircase than in the 400 A run.
• The overtemperature protection tripped during a commanded stop because the slew-limited decay (~50 A/s) leaves hundreds of amps flowing for seconds while the baseplate is still heating. Stopping earlier is the lever — the protection itself worked as designed.
• This session predates the thermal-paste rework of the power stage. The pasted assembly was subsequently validated at 200 A steady state — baseplate plateau 44.4 / 44.0 °C against 22.5 °C ambient — in OV-TEST-HW-REGEN-200A-STEADY-STATE-GEN7-SIZE2.

Conclusion

Pass. Gen7 size 2 hardware sustained a 450 A q-axis regen command at 2,000 RPM — 470 A peak phase current, 12.8 kW average / 13.4 kW peak returned to the DC link, ≈0.283 kWh over 78 s — with no control or gate faults, until the inverter overtemperature protection tripped at 80.1 °C baseplate, duplicating the intended protection behavior of the 200 A OTP report. The open phase-spike observation from the 400 A report is resolved as current-clamp saturation (150 A-rated probes at 400 A), a measurement artifact. Further high-current regen sessions should use appropriately rated current measurement and the thermally-pasted assembly.

Artifacts

• Decimated telemetry log (JSONL, 1 sample/s) — open in Telemetry Viewer
• Telemetry overview plot
• Full source telemetry log, retained for traceability