OBC PFC Magnetics

OBC PFC Inductor Selection and Design Guide: From Single-Phase Totem-Pole to Three-Phase Vienna

Key finding: At 65-140kHz OBC PFC operation, success is usually decided by high-frequency AC loss and permeability roll-off under DC bias, not by DCR alone.

This guide summarizes ProMagTech's OBC PFC inductor design notes for 800V-platform onboard chargers, comparing 11kW single-phase totem-pole PFC and 22kW three-phase Vienna PFC applications.

11kW single-phase totem-pole and 22kW three-phase Vienna PFC inductors

1. OBC PFC Role Boundary

The onboard charger handles AC charging, typically around 6.6kW, 11kW or 22kW. The PFC inductor challenge is not simply current magnitude. The harder problem is controlling loss, temperature rise and inductance retention in the smallest practical volume at the selected switching frequency and DC bias condition.

2. Topology Comparison

11kW single-phase totem-pole PFC
Flat wire winding, iron silicon core, 1.35mH ±10%, 25A rms rated current, saturation current at least 40A, 50kHz to 100kHz operating frequency.
22kW three-phase Vienna PFC
Flat wire winding, composite magnetic core, 0.55mH ±10%, 30A rms rated current, saturation current at least 50A, 50kHz to 100kHz operating frequency.

3. What to Review First

L at peak current
Review inductance retention under peak current and DC bias before trusting no-load inductance.
AC loss
At 65-140kHz, skin effect and proximity effect can drive temperature rise even when DCR looks acceptable.
Core material boundary
FeSi powder core can be cost-effective for 11kW single-phase designs; heavier DC bias in 22kW three-phase designs may require High Flux or other material review.
Thermal condition
Bench-level pass results can fail in sealed OBC environments if enclosure, airflow and mounting are not represented.

4. Engineering Boundary

The values shown here are public engineering reference values from the supplied ProMagTech material. Final PFC inductor selection must be confirmed by converter topology, switching frequency, ripple current, peak current, DC bias, core loss, winding AC loss, insulation requirement, cooling condition and validation data.

Download the PDF Data Report

Download the English OBC PFC inductor selection and design report for engineering review and supplier discussion.

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