One conversation comes up surprisingly often when we talk with drone manufacturers.
The prototype performs well. Bench tests look good. Hover current falls within the expected range. Everything seems to match the calculations made during the design phase.
Then production starts.
A few weeks later, flight testing begins on the first batch of assembled aircraft, and suddenly the numbers don’t line up anymore. Actual flight time ends up 10%, 15%, sometimes even more below what was originally expected.
The first suspects are usually the battery, ESC, propellers, or firmware settings. That’s understandable. Those are the components most people naturally look at first.
But every now and then the real culprit is hidden much deeper inside the motor.
At Kzron, we’ve seen cases where the stator core material was changed during mass production, or where the lamination process wasn’t controlled as carefully as it had been during prototype development. On paper, the motors looked identical. Same dimensions. Same winding specifications. Same magnet setup.
Yet when the motors were tested on a dynamometer, core losses were significantly higher than expected.
That extra energy didn’t disappear.
It turned into heat.
And every watt converted into heat is a watt that never reaches the propeller.
Eventually, that lost energy shows up as shorter flight time, higher motor temperatures, and lower overall efficiency.
The stator core itself doesn’t generate torque. It doesn’t move. It doesn’t contain any electronics. Still, it plays a major role in how efficiently magnetic energy flows through the motor. When the core material is optimized and the laminations are manufactured correctly, the motor operates efficiently. When corners are cut, losses start piling up surprisingly fast.
Where Do Stator Core Losses Actually Come From?
Whenever a brushless motor runs, the stator core is exposed to a constantly changing magnetic field.
That changing magnetic field creates two primary types of losses.
The first is hysteresis loss.
Inside silicon steel, magnetic domains continuously change direction as the magnetic field alternates. Every time those domains realign, a small amount of energy is lost as heat.
The easier those magnetic domains can move, the lower the hysteresis loss becomes.
This is one reason material selection matters so much.
The second type is eddy current loss.
Since silicon steel is electrically conductive, changing magnetic fields induce circulating currents inside the material itself. These currents create heat, just like current flowing through a resistor.
Without any mitigation, eddy current losses can become surprisingly large at high electrical frequencies.
That’s why motor stators are built from thin insulated laminations rather than solid steel blocks.
Each thin layer interrupts the path of circulating currents and dramatically reduces eddy current formation.
Together, hysteresis loss and eddy current loss form what engineers generally call core loss or iron loss.
Unlike copper losses, which increase with load current, iron losses are present whenever the motor is energized. Whether the drone is hovering gently or climbing aggressively, these losses continue consuming power.
Over a 20-minute flight, even small inefficiencies add up.
Why Silicon Steel Grade Matters More Than Many People Realize
Some motor designers focus heavily on magnets, windings, and bearings but treat stator steel as a commodity material.
That approach can work for low-cost applications.
For high-efficiency drone motors, it usually becomes a limitation.
Several key parameters define the quality of electrical steel:
- Material grade
- Lamination thickness
- Core loss rating
- Magnetic permeability
For high-performance UAV motors, Kzron commonly works with materials such as B20AHV1200 and 20SW1200.
Both materials use a 0.20mm lamination thickness and offer relatively low core loss characteristics compared with traditional 0.35mm electrical steel.
Let’s look at B20AHV1200 as an example.
The “20” indicates a thickness of 0.20mm. The material is designed for high magnetic permeability and low iron loss. Its loss value is approximately 1.20W/kg under standard testing conditions.
20SW1200 falls into a similar performance category and has become a widely used option across many motor manufacturing programs.
The reason these materials attract attention is fairly simple.
Thinner laminations reduce eddy current losses.
Lower-loss material reduces hysteresis losses.
When both effects work together, total core loss drops noticeably.
In high-RPM drone motors, moving from conventional 0.35mm laminations to quality 0.20mm material can reduce iron loss by roughly 20% to 30%.
That difference often becomes visible immediately in no-load current measurements.
We’ve seen motors built with B20AHV1200 or 20SW1200 run 0.3A to 0.5A lower no-load current compared with otherwise identical motors using standard 0.35mm electrical steel.
At first glance, half an amp doesn’t sound dramatic.
On a drone that spends most of its life hovering, however, small efficiency gains accumulate throughout the entire flight.
Thickness Matters, But It Isn’t the Whole Story
A common misconception is that thinner laminations automatically mean better motors.
Reality is a bit more nuanced.
Thinner steel does reduce eddy current losses, but it also increases manufacturing complexity and cost.
Producing accurate 0.20mm laminations requires better tooling, tighter process control, and more careful handling.
For high-speed drone motors, the efficiency gain usually justifies the additional expense.
For lower-speed applications, 0.30mm laminations may offer a more balanced solution.
At Kzron, material recommendations are typically based on actual operating conditions rather than marketing specifications.
Target RPM, electrical frequency, efficiency requirements, thermal constraints, and budget all influence the final decision.
There isn’t one perfect material for every motor.
There is only the most appropriate material for a specific application.
Good Material Cannot Fix Poor Lamination Manufacturing
This is where many production issues start.
A customer may specify premium electrical steel, yet the finished motor still performs below expectations.
Often the problem isn’t the material itself.
It’s how the laminations were processed.
The first area is stamping quality.
When silicon steel is punched, the cutting edge must remain clean and precise. Excessive burrs create unwanted electrical bridges between laminations.
Once laminations become electrically connected, eddy currents increase dramatically.
We’ve inspected stators where visible burrs caused measurable increases in temperature and power consumption.
Materials like B20AHV1200 and 20SW1200 are especially sensitive because the thinner sheets require tighter tooling tolerances.
A worn stamping die can quickly create quality issues.
The second factor is stacking factor.
Stacking factor describes how much of the stator volume is actually magnetic material.
Higher stacking factors improve magnetic performance by maximizing effective steel cross-section.
Poor stacking quality leaves unnecessary air gaps, increasing magnetic reluctance and forcing the motor to consume more current to generate the same magnetic flux.
The third factor is interlaminar insulation.
Each lamination includes an insulating coating specifically designed to block current flow between layers.
If that coating becomes damaged during manufacturing, the laminations start behaving more like a solid metal block.
Core losses rise accordingly.
For this reason, Kzron pays close attention not only to material selection but also to stamping quality, burr control, stacking pressure, and insulation integrity throughout production.
What Happens When Iron Loss Gets Too High?
The first consequence is usually reduced flight time.
This is the easiest symptom to notice because it directly affects aircraft performance.
Imagine a drone hovering at 10A average current.
If inefficient stator cores add just 0.5A of unnecessary consumption, that’s already a 5% energy penalty.
Across an entire flight, the effect becomes significant.
The second consequence is higher motor temperature.
Iron losses generate heat directly inside the stator.
That heat eventually transfers through the motor structure and reaches the rotor magnets.
As magnet temperature rises, the risk of demagnetization increases.
Interestingly, we’ve encountered situations where customers repeatedly replaced magnets because thrust gradually decreased over time.
The magnets weren’t necessarily the root cause.
Excessive stator heating was.
The third consequence involves thermal design margins.
A motor running with elevated core losses requires more cooling capacity.
Lightweight motor housings that perform adequately under normal conditions may suddenly struggle to dissipate the extra heat.
The final issue is production consistency.
Prototype motors often receive special attention. Production motors sometimes don’t.
When core materials or lamination quality vary between batches, efficiency variations appear as well.
Some aircraft fly longer.
Some run hotter.
Some simply feel different.
For manufacturers trying to maintain product consistency, that’s a headache nobody wants.
A Real Example: Improving Flight Time Through Stator Core Optimization
One industrial UAV customer approached Kzron with a fairly straightforward goal.
Their hexacopter platform consistently achieved around 22 minutes of flight time.
They wanted at least 24 minutes without increasing battery capacity.
After evaluating the motor design, we identified the stator core as one of the biggest opportunities for improvement.
The original motor used conventional 0.35mm electrical steel.
We recommended switching to B20AHV1200 with a 0.20mm lamination thickness while also improving the lamination process itself.
The updated design included:
- Lower-loss silicon steel
- Improved stacking factor
- Better insulation integrity
- Reduced stamping burrs
Testing produced some interesting results.
No-load current dropped from 1.2A to 0.9A.
Hover current decreased from 11.8A to 10.9A.
Steady-state motor temperature fell by roughly 7°C.
Most importantly, actual flight endurance increased from approximately 22 minutes to 24.5 minutes.
That’s an improvement of about 11%.
The additional motor cost was less than RMB 10 per motor.
For an industrial drone worth tens of thousands of yuan, the return on investment was obvious.
How Can You Tell If the Stator Core Is the Problem?
Diagnosing stator-related efficiency issues isn’t always complicated.
One useful method is measuring no-load current.
Run the motor at a fixed voltage without a propeller attached. Excessively high no-load current often points toward elevated core losses.
Thermal imaging can also reveal problems.
If stator temperatures rise unusually quickly during unloaded operation, iron loss may be higher than expected.
Physical inspection provides additional clues.
Look for rust, visible burrs, loose laminations, or mechanical damage.
Any of these issues can negatively affect performance.
When available, back-to-back testing remains the most reliable approach.
Comparing motors built with different stator materials under identical conditions quickly reveals whether core performance is contributing to efficiency differences.
What Does Kzron Supply?
Kzron manufactures stator cores for a wide range of UAV motors, from compact FPV platforms to large industrial propulsion systems.
Material options include premium grades such as B20AHV1200 and 20SW1200, along with conventional 0.30mm and 0.35mm electrical steels depending on application requirements.
Our production process focuses heavily on consistency.
High-precision stamping tools help minimize burr formation. Lamination stacking parameters are carefully controlled. Critical dimensions are inspected throughout production, and finished stators undergo appearance and dimensional verification before shipment.
Some customers provide complete engineering drawings.
Others send existing motor samples and ask us to reverse engineer the stator core.
We support both approaches.
For production programs, material certificates and dimensional reports can be supplied with each batch.
A Few Practical Suggestions for Engineers and Purchasing Teams
One thing we’ve learned over the years is that vague specifications almost always create problems later.
If a motor requires B20AHV1200 or equivalent material, write that requirement directly into the drawing.
Don’t simply specify “high-quality silicon steel.”
Request material certificates.
Ask for traceability.
Verify lamination thickness rather than assuming it matches the quotation.
Production consistency matters just as much as prototype performance.
It’s also worth inspecting actual stator quality when evaluating suppliers. Burrs, oxidation, deformation, and poor stacking quality often reveal more about manufacturing capability than marketing brochures ever will.
And finally, don’t focus exclusively on material cost.
A slightly more expensive stator core that improves efficiency by several percent can easily pay for itself through longer flight times, lower temperatures, and improved customer satisfaction.
Final Thoughts
When people discuss drone motor performance, the conversation usually revolves around magnets, winding design, KV ratings, or propeller selection.
The stator core rarely gets the same attention.
Yet it has a direct influence on power consumption, motor temperature, efficiency, and ultimately flight endurance.
The material establishes the theoretical performance limit.
The lamination process determines whether that performance actually reaches production.
A well-designed motor using low-loss materials such as B20AHV1200 or 20SW1200 can consume less power, generate less heat, and convert more battery energy into useful thrust. Over the course of an entire flight, those gains become surprisingly noticeable.
At Kzron, stator core manufacturing is more than simply stamping steel sheets. Material selection, lamination quality, dimensional accuracy, and process consistency all play a role in the final result.
Sometimes extending flight time doesn’t require a larger battery or a more powerful motor.
Sometimes it starts with something much simpler.
A better stator core.
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