Powder Metal Resources

Beyond Start-Stop: How Advanced Motor Designs Improve HVAC Efficiency and Reduce Noise

Written by Horizon Technology | Feb 3, 2026 3:15:00 PM

The Challenge: Stop-Start Inefficiency in Modern HVAC Systems

Most HVAC systems, whether in commercial buildings or residential applications, still rely on motors that cycle on and off throughout the day. This start-stop behavior, inherited from older control logic and motor technology, creates more than just noise. It’s a major source of inefficiency, mechanical wear, and acoustic vibration.

Each startup draws a surge of current, generates heat, and stresses key components like bearings, insulation, and windings. Multiply that across thousands of cycles per year, and you have a clear picture of why many systems operate below their potential lifespan—and below optimal efficiency.

In fact, most HVAC motors spend the majority of their operational life at part-load conditions, where traditional laminated steel designs perform least efficiently. The result is a system that wastes energy precisely when it should be running most economically.

The Shift Toward Continuous, Variable-Speed Operation

To address this, the industry has been moving steadily toward variable-speed HVAC systems. Rather than cycling on and off, these systems adjust speed to match real-time demand.

This approach delivers several measurable benefits:

  • Higher efficiency at partial load, where HVAC systems operate most of the time
  • Smoother airflow and more consistent comfort
  • Reduced mechanical stress from constant starts and stops
  • Lower noise, vibration, and harshness (NVH) for quieter, longer-lasting equipment

But here’s the challenge: while variable-speed drives can control motor speed, the motor core itself, which is typically made from laminated steel, often limits how much efficiency can actually be realized. That’s where design innovation becomes essential.

The Core Problem: Traditional Materials, Modern Demands

Traditional laminated steel motor cores were never optimized for continuous, variable-speed operation. The 2D magnetic path inherent in stacked laminations leads to increased eddy current losses and thermal buildup when frequency and speed fluctuate.

These losses don’t just waste energy; they directly reduce torque stability and increase unwanted vibration and acoustic noise. It’s an engineering bottleneck that control systems alone can’t fix. To truly improve variable-speed performance, we need to address the issue at its source: the magnetic architecture of the motor itself.

The Breakthrough: Soft Magnetic Composites

Soft magnetic composites (SMCs) are a modern engineering material made from iron powder particles coated with an insulating layer and compacted into precise 3D shapes.
This structure allows magnetic flux to flow in three dimensions (not just along a plane) and dramatically reduces eddy current losses—especially at higher frequencies. In other words, SMCs make it possible to design motors that are inherently suited for variable-speed operation.

How SMC-Enabled Designs Improve Continuous Operation

When applied to advanced motor topologies such as axial flux, yokeless axial flux, or trapezoidal radial flux designs, SMCs enable several key advantages:

  • Smoother Torque Delivery
    The 3D magnetic pathways allow more uniform flux distribution, reducing torque ripple and mechanical noise at low speeds.
  • Higher Efficiency at Variable Frequencies
    By minimizing eddy current losses, SMC-based motors maintain efficiency across a wider operating range, making them ideal for systems that modulate airflow or compressor load continuously.
  • Lower NVH and Longer Life
    Reduced heat generation and vibration lessen fatigue on bearings and insulation, translating to quieter, more reliable operation.
  • Manufacturing Simplicity and Scalability
    Net-shape geometries enable the use of pre-wound bobbins, simplifying assembly while maintaining precision, which is essential for cost-effective production at scale.

Realistic, Proven Gains (Not Theoretical Promises)

Recent studies show that well optimized SMC-based motors can deliver 2–4% higher system efficiency compared to conventional small-frame HVAC motors, particularly under variable-speed operation. That gain may sound modest, but in systems running thousands of hours per year—and in facilities where cooling can account for 40% of total energy use— it translates into meaningful, measurable savings. The combination of continuous operation, smoother performance, and quieter function offers both energy and experiential improvements that make a tangible difference in the market.

From Incremental to Intentional Design

The next leap in HVAC innovation won’t come from smarter control boards or incremental software updates; it will come from rethinking the motor itself. At Horizon Technology, our focus is on engineering manufacturable, high performance solutions that transform how HVAC systems operate. By combining design freedom with practical manufacturability, we help our partners create systems that don’t just meet efficiency targets; they set new standards for how efficiency feels, sounds, and performs.

The future of HVAC efficiency isn’t about turning off and on; it’s about moving forward continuously. At Horizon, we’re engineering that momentum.