Motor performance degradation and power loss at elevated temperatures are rarely caused by design flaws — more often than not, the root cause lies in the wrong ferrite magnet grades selection.

Yet most buyers and engineers still rely on room-temperature logic when selecting materials for high-temperature applications: they judge magnet quality by Br (remanence) alone. That works at 25°C. But once the motor runs hot for extended periods, a mismatched grade can lead to batch failures, costly rework, and delayed deliveries.

This article cuts through the confusion with a direct comparison of the two most common high-coercivity ferrite grades — Y30BH and Y35 — helping you skip the spec-sheet headaches and find the right fit for your project.

For High-Temperature Selection, Coercivity Comes First – Not Remanence

At room temperature, remanence is the go-to metric. But in high-temperature environments, intrinsic coercivity is the real gatekeeper — a principle many buyers know in theory but still get wrong when staring at spec sheets.

Remanence determines output. Coercivity determines how long that output lasts. When the motor heats up, the armature reaction generates a reverse magnetic field. If coercivity isn't high enough, irreversible demagnetization occurs — and once that happens, the lost magnetism never comes back.

The logic is brutally simple: first verify that coercivity can handle the worst-case demagnetization risk, then check whether remanence meets the motor's torque and power requirements.

Ferrite's Unique Advantage at High Temperatures

Ferrite magnets have a characteristic that neodymium magnets simply don't: their coercivity increases as temperature rises.

The temperature coefficient for ferrite Hcj is approximately +0.27% to +0.4%/°C, while remanence decays at roughly -0.18% to -0.2%/°C. The core of high-temperature ferrite selection is this: choose a grade with sufficient coercivity to prevent demagnetization at the maximum operating temperature, within the acceptable remanence loss range.

By contrast, neodymium magnets experience a sharp drop in both remanence and coercivity at elevated temperatures — often requiring expensive heavy rare-earth additions or complex cooling systems to maintain performance. Ferrite requires none of that, making it the more reliable and cost-effective choice for continuous high-temperature operation.

Y30BH vs. Y35 – Which One Is Right for You?

The two most widely available high-coercivity sintered ferrite grades on the market are Y30BH and Y35. They serve different purposes — pick the right one and you save cost; pick the wrong one and you risk scrapping entire batches.

Y30BH – The Cost-Effective All-Rounder

Magnetic properties: Br 380–390mT, Hcj 231–245kA/m, maximum operating temperature 180–200°C.

Y30 and Y30BH are the most commonly used ferrite grades on the market — highest shipment volumes, most mature production processes. That means consistent batch quality, short lead times, and low rejection rates — critical factors for large-volume procurement. If your project doesn't have extreme requirements, starting with Y30BH gives you the lowest trial-and-error cost.

Ideal applications: Home appliance motors, cooling fans, circulation pumps, inverter compressor motors.

Y35 – Higher Flux Output for Power-Dense Designs

Magnetic properties: Br 400–410mT, Hcj 180–200kA/m, (BH)max 7%–11% higher than Y30BH, maximum operating temperature above 200°C.

Y35 delivers stronger magnetic flux output — about 5% higher remanence than Y30BH, though with slightly lower coercivity. It's the better fit for applications with hard torque or power density requirements. The price premium over Y30BH is typically 10%–15%. Whether that premium is worth it depends on your motor design: if a flux boost allows for a smaller motor frame or higher efficiency, the extra cost pays off; if thermal margin is sufficient and torque requirements are moderate, Y30BH offers better value. The choice comes down to your design priorities.

Ideal applications: Industrial equipment operating at elevated temperatures with clear magnetic strength requirements.

Quick Selection Summary

Y30BH – Higher coercivity (231–245kA/m) and better demagnetization resistance. Safer choice for high-temperature or high-reverse-field environments.

Y35 – Higher remanence (400–410mT) and 7%–11% higher energy product, but lower coercivity (180–200kA/m) and a 10%–15% price premium.

Bottom line: Choose Y30BH when demagnetization resistance is the priority. Choose Y35 when power density justifies the extra cost.

Supplier Capability: Delivery and Customization

Getting the grade right is only step one — whether your supplier can deliver consistently and handle custom shapes is what determines whether your project actually succeeds.

Kaiven Magnetics has over 30 years of ferrite manufacturing experience, with an annual output of nearly 30,000 metric tons of ferrite and 2,000 metric tons of sintered neodymium — giving it the scale and technical depth to handle both high-volume standard orders and low-volume custom projects.

Y30BH, Y35, and all other mainstream high-coercivity grades are available for stable mass production. Y30BH has the shortest and most reliable lead times. Beyond standard shapes, Kaiven supports full integration of grade selection + custom configurations — motor arc segments (magnetic tiles), rings, blocks, and custom-shaped/slotted magnets are all available for tooling and production. With proven processes for large-arc magnetic tiles and ultra-thin wall ferrite components, Kaiven effectively addresses common industry challenges like sintering cracks and dimensional tolerance control.

In other words, you don't need to source grades from one supplier and shapes from another — Kaiven handles both under one roof.

The cooperation process is straightforward:

Send your product drawings and complete operating parameters.

The engineering team assesses manufacturability and grade fit.

You receive a formal proposal and quotation.

Summary & Next Steps

Irreversible demagnetization in high-temperature motors is almost always a ferrite grade selection issue — not a motor design flaw. The room-temperature habit of prioritizing remanence simply doesn't work at elevated temperatures. Coercivity must be the primary filter. Y30BH is the right choice for standard high-temperature applications where demagnetization resistance is critical; Y35 is the better fit for power-density-critical applications where a moderate cost increase buys higher flux output. Choose the correct grade, and you cut costs and reduce R&D risks; pick the wrong one, and you face costly batch scrapping losses.

Kaiven Magnetics has helped numerous high-temperature motor manufacturers navigate grade selection, sample validation, and volume production. Instead of going back and forth over spec sheets on your own, let a team with over 30 years of ferrite experience do the matching for you.

Simply provide your key operating parameters — maximum continuous operating temperature, motor type, mounting structure, and dimensional requirements — and Kaiven's engineering team will deliver a tailored ferrite grade recommendation and cost analysis. It saves you time, effort, and trial-and-error costs.