Traction Inverter¶

Overview¶

The traction inverter converts DC from the battery to three-phase AC to drive the electric motor. High efficiency, power density, and reliability are critical for vehicle performance and range.

Difficulty: Advanced

Status: Placeholder

Specifications¶

Parameter	Value	Unit
DC Voltage	400 or 800	VDC
Peak Power	150-350	kW
Continuous Power	100-250	kW
Peak Efficiency	>97%	-
Switching Frequency	8-20	kHz
Power Density	>30	kW/L

Topology¶

Standard 2-Level VSI¶

         Battery
      +Vdc    -Vdc
        │      │
    ┌───┴──────┴───┐
    │   Inverter   │
    │  ┌──┬──┬──┐  │
    │  │  │  │  │  │
    │  A  B  C  │  │
    └──┼──┼──┼──┴──┘
       │  │  │
    ┌──┴──┴──┴──┐
    │   PMSM    │
    │  Motor    │
    └───────────┘

800V Systems¶

Benefits of 800V vs 400V: - Half the current for same power - Smaller cables, connectors - Faster DC charging - Higher efficiency

Challenges: - Component availability - Increased insulation requirements

SiC vs Si-IGBT¶

Parameter	Si-IGBT	SiC MOSFET
Switching loss	Higher	70% lower
Switching freq	8-12 kHz	15-25 kHz
Efficiency	95-96%	97-98%
Cost	Lower	Higher (decreasing)
Thermal	175°C Tj	200°C+ Tj

Control: Field-Oriented Control (FOC)¶

Speed Ref ─►[PI]─► Iq_ref ─►[PI]─► Vq ─►[Inverse]─► Va,Vb,Vc ─►[SVPWM]─► PWM
                      │              │     Park                    │
              Id_ref=0│              │                             │
                ─────►[PI]─► Vd ─────┘                             │
                      │                                            │
                      └◄─────[Park]◄─────[Clarke]◄─────[Current]◄──┘
                              dq            αβ          Measure
                               │
                          θe ──┘ (from resolver/encoder)

Key Control Features¶

Feature	Purpose
MTPA	Maximum torque per ampere
Field weakening	Extend speed range
Dead-time compensation	Reduce distortion
Active damping	Suppress resonance

Thermal Design¶

Cooling Requirements¶

P_loss = P_cond + P_sw ≈ 3-5% of P_out

For 200kW inverter:
  P_loss ≈ 6-10 kW
  Requires liquid cooling with ~50°C ΔT

Cooling Options¶

Method	Heat Dissipation	Use Case
Air cooled	<5 kW	Low power
Liquid (glycol)	5-15 kW	Standard EV
Direct oil cooling	>15 kW	High performance
Two-phase	Highest	Racing/aerospace

PMSM Motor Parameters¶

Parameter	Symbol	Typical Value
Pole pairs	p	4-8
Stator resistance	Rs	5-20 mΩ
d-axis inductance	Ld	100-500 μH
q-axis inductance	Lq	100-500 μH
PM flux linkage	λm	50-150 mWb
Max speed	nmax	12000-18000 RPM

Exercises¶

Exercise 1: Basic Inverter¶

Build 400V, 100kW 2-level VSI
Apply SPWM modulation
Measure output THD

Exercise 2: FOC Implementation¶

Add PMSM model
Implement d-q current control
Test torque step response

Exercise 3: Efficiency Map¶

Sweep speed and torque
Calculate losses at each point
Generate efficiency map

Circuit Files¶

Status: Placeholder - traction_inverter_basic.ipes - Open-loop SPWM - traction_inverter_foc.ipes - With FOC control - traction_pmsm_system.ipes - Complete drivetrain

Placeholder - Details to be added