EV Power Magnetics: Inside the Inverter, the Charger, and the Auxiliary Electronics

Electric vehicle development moves fast, and the magnetics inside an EV are some of the hardest components to get right on a compressed timeline. High-voltage battery packs, rapid charge cycles, SiC and GaN switching at hundreds of kilohertz, and a thermal environment that swings constantly all packed into a platform with tight weight, space, and EMC budgets. Catalog parts weren’t designed for any of that.

Custom Coils USA builds the small-format magnetics that live inside EV power electronics: gate drive transformers, pulse transformers, flyback supplies, signal-level isolation transformers, and the inductors that go alongside them. We’re a VPI dry-type specialty shop with transformers up to about 2 kVA. We don’t build the main HV-LV isolation transformer in a multi-kilowatt onboard charger or any traction-stage iron  those are different product classes. We build the magnetics inside those subsystems, and the parts engineering teams need for development, prototype, specialty-platform, and test/validation hardware.

Power Magnetics Across the EV Platform

EV Inverter Magnetics: Gate Drive, Sense & Auxiliary Transformers

EV traction inverters don’t carry power through transformers  DC battery in, AC out to the motor, no main-path iron. The transformers inside the inverter are the small ones that determine whether the converter starts, switches cleanly, and reports to its controller. Gate drive transformers couple control signals into IGBT, SiC, or GaN switch stages with the propagation delay, common-mode transient immunity, and isolation rating each technology demands. Current and voltage sense transformers feed measurement and protection electronics. Auxiliary control-power transformers run housekeeping rails. We build all three to your topology, switching frequency, and HV bus rating.

Pulse Transformers for Gate Drive Circuits

Pulse transformers couple the gate signal across the HV-LV barrier with the rise time, isolation rating, and CMTI margin your switch device requires. SiC and GaN devices run dV/dt rates of tens of kV/μs that punish a barrier that wasn’t built for them  interwinding capacitance, shielding, and core material all matter. Wound to the bus voltage, isolation class, and switching profile your design specifies.

Flyback Transformers for Auxiliary Electronics

Auxiliary supplies inside the EV instrument cluster, infotainment, body control, low-voltage subsystems  typically run flyback topologies because they’re compact, isolated, and well-suited to the wide input voltage range an automotive bus presents. We build flyback transformers spec’d for the input voltage range, output regulation, and thermal envelope of your specific subsystem, with leakage inductance and creepage distances designed to your isolation requirements.

Isolation Transformers for Low-Power HV-LV Barriers

We build the lower-power isolation transformers that sit at HV-LV boundaries auxiliary supply isolation, BMS cell-monitoring isolation, sensor isolation, and signal-level barrier crossings. Insulation systems and creepage distances are matched to your HV bus class and the fault conditions your architecture defines. The main multi-kilowatt isolation transformer in the OBC power path is outside our scope that’s a different product class.

Inductors for OBC, DC-DC Converters & Filter Stages

Inductors and chokes wound with low AC resistance and core materials matched to your switching frequency, for onboard charger sub-stages, auxiliary DC-DC converters, and filter elements. Silicon steel, ferrite, amorphous, and nanocrystalline cores available  designed against the actual current waveform and thermal environment in your application, not a generic catalog rating.

What EV Engineering Teams Tell Us They Actually Need

• Parts designed around the real operating conditions : not extrapolated from catalog ratings that ignore thermal cycling, dV/dt stress, and saturation in service
• USA manufacturing with 4–8-week lead times : domestic supply chain matters when a development program is running to a deadline
• Built to your specified UL system, with full component-level documentation : insulation class, materials, electrical test data, samples  supporting the customer-led recognition and qualification path for your end product
• Engineers on the phone, not sales staff : if your inverter topology is unusual, you need someone who can discuss it

Frequently Asked Questions

Q1: What types of magnetics go into a modern EV?

Inside the traction inverter: gate drive transformers, current/voltage sense transformers, and auxiliary control-power transformers. Inside the OBC and DC-DC stages: filter and resonant inductors, gate drive and pulse transformers, and signal-level isolation. In the auxiliary electronics: flyback supplies and signal isolation. The main HV-LV isolation transformer in an OBC and the main filter inductor in a multi-kilowatt charging stage are typically outside our scope  those are higher-power product classes.

Q2: Why do EV onboard chargers need custom inductors rather than catalog parts?


Because the actual current waveform a real OBC runs is different from the catalog spec. Switching frequency, resonant operation, and the duty profile your charge algorithm executes all change saturation and thermal behavior. Designing against the real waveform  not a generic kHz rating  is what keeps the inductor from becoming a warranty issue.

Q3: How does galvanic isolation protect vehicle electronics in an EV?


An isolation transformer puts a galvanic break in the electrical path between the high-voltage battery system and the low-voltage electronics. A fault on the HV side can’t conduct through the barrier, and common-mode noise from the HV bus is decoupled from the LV signal path.

Q4: What makes SiC gate drive design harder than standard IGBT applications?


The dV/dt. SiC switches transition tens of kV/μs at the drain, and that fast edge couples capacitively across any imperfect isolation barrier as common-mode current. The pulse transformer needs low interwinding capacitance, high common-mode transient immunity (CMTI), and a winding geometry that doesn’t ring at the switching transitions. GaN is even tighter.

Q5: What are your lead times for custom EV magnetics?


4–8 weeks from finalized specification to delivery for prototype and low-volume work. Engaging us early in your design cycle is the easiest way to keep magnetics off the critical path during development.