1Device & topology

DeviceParameters transcribed from the manufacturer datasheet — still editable below.

Parallel devices per position6 discrete devices (6 positions × 1 in parallel)

Device current rating (A)

RDS(on) @25°C (mΩ)

RDS(on) hot (mΩ)

Hot temp (°C)

Eon (mJ)

Eoff (mJ)

E test pointThe VDD and ID at which the datasheet measured Eon/Eoff (and Err). The engine scales energies linearly in current and by (Vdc/Vtest)^kv in voltage from this point.

Err (mJ)Body-diode reverse recovery energy at the same test class. Set 0 if the datasheet only gives Qrr — the engine then uses Err ≈ Qrr·Vdc/4.

Qrr (µC)

VSD body diode (V)

RthJC (K/W)

Tvj max (°C)

QG total (nC)

Transcribed from the IMBG120R008M2H datasheet (v1.10): Eon 1.28 mJ/Eoff 0.81 mJ at VDD=800 V, ID=89.9 A, VGS=0/+18 V, RG,ext=2.3 Ω; Qfr 2.1 µC and Efr 0.28 mJ at 175 °C used as Qrr/Err; 200 °C cumulative-overload capability. RthJC estimated from package class (datasheet grep returned Rth(j-a) only) — verify.

2Operating point

DC bus voltage (V)

Switching frequency (kHz)

Modulation index (m)0-1 for pure sinusoidal PWM; up to ~1.15 with space-vector or third-harmonic-injection modulation.

Power factor |cosφ|

Dead time (ns)

Case/heatsink temperature (°C)

Heatsink temperature sourceKnown value: type the case/heatsink temperature directly. Coolant flow: derive it instead from a coolant inlet temperature, total loop flow rate, and a heatsink-to-fluid convective resistance Rsc — the bulk fluid rise scales with all 6·n switch positions sharing the loop (mean-fluid convention, same as the Cold Plate calculator), while Rsc is the local per-device spot resistance.

Cooling mountDirect cooling: the device's RthJC already spans case to coolant (baseplate-less modules, or a discrete tab pressed straight to a cold plate). TIM + baseplate: models an added solder or sintered-silver interface between the device case/baseplate and the heatsink, on top of RthJC.

Motor pole pairs

Motor/generator speed (rpm)f1 = 400 Hz — context; the analytical loss averages hold for any f1 ≪ fsw

Synchronous rectificationSiC MOSFET channels conduct in reverse when gated on, so complementary (synchronous) gating is the normal way to run an inverter leg. With it ON, total losses are symmetric between motoring and generating; turn it OFF to see the classic channel/body-diode conduction split, where the motor/generator difference is explicit.

Voltage scaling exponent (kv)Eon/Eoff scale as (Vdc/Vtest)^kv from the datasheet test voltage. Datasheet energy-vs-voltage curves are typically slightly superlinear (~1.2-1.4); 1.0 (linear) is the conservative default when Vdc is below the test voltage.

3Load / simulation

Phase current (A rms)

Mode

Results

Per-device die loss

48.8W

RDS(on) used: 11.15 mΩ

Whole-inverter loss

293W

6 discrete devices (6 positions × 1 in parallel)

Junction temperature

73.8°C

case 65°C, RthJC 0.18 K/W

Output power

62.6kW

Efficiency

99.535%

Loss breakdown

Conduction (channel)Conduction (body diode)Dead-time diodeSwitching (Eon+Eoff)Reverse recovery

Reference & assumptions

New to SiC Inverter Loss? Read the guide: SiC Inverter Losses: Conduction, Switching & Reverse Recovery — a plain-language explainer of the standard behind this calculator.

Standard analytical loss equations for a 2-level, 3-phase, sinusoidal-PWM voltage-source inverter. With synchronous rectification on (the normal way to run SiC), each leg device conducts half the fundamental period through its channel, so total losses are symmetric between motoring and generating — the motor/generator distinction appears explicitly in the classic channel/body-diode split when sync rect is off, and in the duty-cycle profile either way. Switching energies scale linearly with current and by (Vdc/Vtest)^kv with voltage from the datasheet test point, and are held temperature-independent (SiC Eon/Eoff vary only weakly with Tvj — e.g. CAB450M12XM3 shows 25.4→24.4 mJ across 25→175°C). Reverse recovery uses datasheet Err where published, else the standard Qrr·Vdc/4 soft-recovery approximation. Gate-drive loss is dissipated in the driver and gate resistors, not the die, and is excluded from the junction-temperature solve. Devices flagged with ⚠ carry verified headline specifications (part number, package, RDS(on), rating) but representative loss parameters — transcribe the real datasheet values (the field-mapping guide lives at the top of sicDevices.ts) before trusting absolute numbers. Screening tool — not a substitute for double-pulse characterisation or calorimetric inverter testing.

Validated: every loss equation (sync-rect and classic channel/diode conduction — the standard Casanellas PWM-loss form — dead-time diode conduction, test-condition-normalized switching and reverse-recovery loss, gate-drive loss, Rds(on) temperature interpolation, and inverter output power) was independently re-derived from its documented formula and matched the calculator's output exactly across a full set of hand-picked test cases.

Calculation steps

1. Per-device current share

Irms_dev = Irms_phase / n, Ipk_dev = √2 · Irms_dev

n = 1 parallel per position

Irms_dev = 82 A, Ipk_dev = 116 A

2. Conduction loss (synchronous rectification)

P_cond = RDS(on)(Tj) · Irms_dev² / 2 — channel conducts both directions; each leg device conducts half the period, so m and cosφ drop out

RDS(on) at Tj = 73.8°C → 11.15 mΩ (interpolated 7.7 mΩ @25°C → 18.3 mΩ @175°C)

P_cond = 37.48 W per device

3. Dead-time body-diode conduction

P_dt = VSD · (Ipk_dev/π) · 2·td·fsw — two dead-time intervals per switching period carry the load current through the body diode

VSD = 4.2 V, td = 500 ns, fsw = 10 kHz

P_dt = 1.55 W per device

4. Switching loss (Eon + Eoff)

P_sw = fsw · (Eon+Eoff) · (Vdc/Vtest)^kv · Ipk_dev/(π·Itest) — linear in current; energies held temperature-independent (SiC Eon/Eoff vary only weakly with Tvj)

Eon+Eoff = 2.09 mJ @ 800 V/89.9 A, Vdc = 800 V, kv = 1

P_sw = 8.58 W per device

5. Reverse recovery loss

P_rr = fsw · Err · (Vdc/Vtest)^kv · Ipk_dev/(π·Itest) — datasheet Err, dissipated in the hard-turning-on device

Err = 0.28 mJ @ 800 V/89.9 A

P_rr = 1.15 W per device

6. Gate drive loss (informational — dissipated in the driver/gate resistors, not the die)

P_gate = QG · ΔVGS · fsw

QG = 195 nC, ΔVGS = 18 V

P_gate = 0.035 W per device

7. Cooling mount

Direct cooling — RthJC already spans case to coolant (baseplate-less module, or a tab pressed straight to a cold plate)

RthJC = 0.18 K/W

No added TIM resistance

8. Junction temperature (fixed-point iteration)

Tj = T_ref + P_die · (RthJC), RDS(on)(Tj) re-evaluated each pass until converged

T_ref = 65°C (known case/heatsink temp), RthJC = 0.18 K/W, P_die = 48.76 W

Tj = 73.8°C vs Tvj(max) 175°C — pass

9. Inverter totals and efficiency

P_inverter = 6·n·P_die; P_out = 3·(m·Vdc/2√2)·Irms·|cosφ|; η = P_out/(P_out + P_inverter)

6 × 1 devices, Irms = 82 A

P_inverter = 292.5 W, P_out = 62.6 kW, η = 99.535%

MOSFET Loss Calculator (1200 V SiC Inverter)