Nanocrystalline Cores for EMI Suppression in EV Heater Systems – Design Guid

In electric vehicle (EV) thermal management systems, the EV heater is a key high-voltage component. However, its switching operation and high power levels generate significant electromagnetic interference (EMI), which can impact overall electromagnetic compatibility (EMC) compliance.

 

Among available magnetic materials, iron-based nanocrystalline cores (such as FINEMET®， 1K107B) are increasingly popular for common-mode chokes (CMCs), current transformers, and localized magnetic shielding. Their high permeability, low loss, and thermal stability make them especially effective in specific EMI suppression scenarios.

 

When to Use Nanocrystalline Cores

• Dominant Common-Mode Noise (10 kHz – 5–10 MHz): Ideal for HV input lines and harnesses between EV heater, DC/DC converter, and OBC.
• High-Temperature Environments: Stable performance at 85–105°C.
• Compact Size Requirements: Smaller core size or fewer turns to meet impedance targets.
• Localized Magnetic Shielding: Tape-wound shields reduce leakage flux and radiated EMI.

When Not to Use (or Use with Caution)

• Differential-Mode Filtering/Energy Storage: Susceptible to DC saturation; better use gapped ferrite or powder cores.
• Very High Frequency EMI (>10–20 MHz): NiZn ferrite often more cost-effective.
• Harsh Mechanical Shock/Cost-Sensitive: Brittle and higher cost; requires careful mounting.

Typical EV Heater Applications

HV+/HV− Common-Mode Choke

1. Measure noise spectrum using LISN and CISPR 25 limits.
2. Calculate impedance target and required inductance.
3. Check leakage inductance, temperature rise, and saturation margin.

Harness Clamp-On Cores

Installed close to noise sources or chassis entry points; affects only common-mode currents.

Localized Magnetic Shielding

Wrap tape shields around noisy components; ground appropriately to reduce coupling.

Material Comparison Table

For more details about nanocrystalline core info., click https://www.amorphousoem.com/product/fe-based-1k107-42525mm-nanocrystalline-bead-for-spike-suppression