Mr. Don Currie reports

HILLCREST ZVS TECHNOLOGY DEMONSTRATES MORE THAN 90% REDUCTION IN MOTOR VOLTAGE SPIKES

Hillcrest Energy Technologies Ltd. has released peer-reviewed test results quantifying the performance of its zero-voltage-switching inverter technology against a conventional hard-switched silicon carbide inverter. In side-by-side testing, ZVS reduced motor terminal voltage overshoot by more than 90 per cent from 1.5 per unit to 1.04 pu of direct-current-link voltage and reduced high-frequency electromagnetic interference above five megahertz by approximately 25 decibels.

The results are documented in a peer-reviewed paper accepted for the IEEE Energy Conversion Congress and Expo, a leading international conference in power conversion. Dr. Emanuel Serban, Hillcrest's vice-president of engineering, will present the paper at the event, to be held Oct. 4 to Oct. 8, 2026, in Vancouver, B.C.

Commercial significance

Drive manufacturers are moving from silicon to wide-bandgap semiconductors, principally SiC, to gain efficiency, switching frequency and power density. The paper documents the engineering penalty that accompanies this transition: because SiC devices switch far faster than silicon, impedance mismatch among inverter, cable and motor produces repeated voltage reflections, and motor terminal voltage can reach twice the DC link voltage even with cable lengths of only a few metres.

The consequences carry commercial weight. The paper states that these voltage oscillations accelerate insulation aging, promote partial discharge activity and ultimately lead to premature failure of inverter-fed motor windings, which translates into warranty exposure for equipment makers and unplanned downtime for end-users. The standard mitigation is passive filtering at the motor terminals or the inverter cabinet. As the paper notes, while such filters are effective, they add cost and size to the drive system and incur extra power losses, which offset the inherent advantages of wide-bandgap technology.

Hillcrest's ZVS approach addresses the problem at the switching event rather than downstream of it. By commutating each device when the voltage across it is near zero, the platform extends the voltage transition roughly tenfold while preserving high efficiency, whereas conventional slew rate reduction through snubber circuits increases switching losses and degrades efficiency. For drive original equipment manufacturers evaluating SiC platforms, these results provide a quantified basis for comparing ZVS against added filtering hardware.

Where the results apply

The overvoltage findings apply to cable-fed drive systems, where the inverter is cabinet mounted and connected to the motor by a cable of meaningful length. The effect scales with cable length, so the benefit is greatest in factory automation and robotics, conveyor and material handling systems, packaging machinery, automated assembly lines, cabinet-driven industrial pumps and fans, and electric vehicle and rail traction systems.

The emissions and slew rate results are independent of cable length and apply to any SiC inverter platform.

Detailed findings

Against a conventional hard-switched SiC inverter, the ZVS platform delivered:

• Overshoot reduction of more than 90 per cent: Motor terminal overshoot fell from 1.5 pu to 1.04 pu with an 80-kilowatt motor on a two-metre shielded cable at 400 volts DC and 20 kilohertz. Overshoot is the peak voltage the motor insulation actually sees, expressed relative to DC link voltage.
• An order-of-magnitude reduction in dv/dt: Slew rate fell from approximately 16 V/ns to 1.4 V/ns at 470 V DC and 40 kHz. Because inverter output voltage rise time has been shown to have a dominant influence on the severity of reflected wave overvoltage, this is the mechanism behind the overshoot result.
• Up to 25 dB lower high-frequency emissions: Above five MHz, emissions were roughly 25 dB below the hard-switched reference. Between one and five MHz, the ZVS platform's emissions were five to 25 dB lower; below one MHz, the two platforms were comparable. Reduced high-frequency content is where EMI filtering and shielding costs concentrate.
• Controlled voltage on long cable runs: Under worst-case double-pulse conditions with a 50-metre cable at 470 V DC, peak load voltage remained below 2 pu at approximately 920 V. The paper notes that published research reports hard-switched inverters exceeding two to three pu under comparable narrow-pulse conditions.

Slower switching transitions also allow longer cables. Every drive has a critical cable length, beyond which reflected waves can double the voltage at the motor. For the configuration analyzed, ZVS extends that limit to approximately 18 metres, giving machine builders more flexibility in cable routing and cabinet placement.

Broader ZVS platform results

The reflected wave findings build on the results Hillcrest has previously reported for its ZVS technology in separate testing and research:

• Efficiency: up to 99.7 per cent peak inverter efficiency, confirmed in testing at the facilities of global automotive OEMs and Tier 1 suppliers; this indicates that the controlled switching transitions described in the paper are compatible with very high efficiency;
• Electromagnetic interference: chamber testing at a certified external laboratory selected by a European automotive OEM found substantially lower EMI than conventional inverters across all tested operating points;
• Passive component reduction: by largely eliminating switching losses, ZVS supports higher switching frequencies, in which Hillcrest's published research has shown reduced DC link capacitor size and ripple-related heating, with benefits for drive cost, volume and component lifetime.

Together with the ECCE 2026 results, these findings indicate that ZVS can address efficiency, electromagnetic interference and motor insulation stress within a single architecture. Drive designers often have to trade these attributes off against one another.

Management commentary

"Reflected wave overvoltage limits the use of high-efficiency, high-speed power semiconductors in motor drives with long cables. Conventional solutions require additional filters, increasing system cost, size and complexity. Our solution simplifies the drive design while enabling the use of advanced, high-efficiency semiconductor devices," said Dr. Emanuel Serban, vice-president of engineering at Hillcrest Energy Technologies. "Controlling dv/dt at the switching event removes the cause instead of treating the symptom. Both theoretical analysis and experimental results demonstrate a significant reduction in EMI and motor terminal overvoltage in cable-fed systems."

"Peer-reviewed validation is what drive manufacturers require before committing to a new power conversion architecture," said Don Currie, chief executive officer of Hillcrest Energy Technologies. "Presenting these results puts quantified evidence in front of exactly the engineering audience that makes those decisions. Combined with the efficiency and EMI performance already demonstrated in OEM testing, these results strengthen the case for ZVS across a broad range of motor drive applications."

About Hillcrest Energy Technologies Ltd.

Hillcrest is a Canadian clean technology company developing advanced power conversion technologies and digital control systems for next-generation energy applications, including AI data centres, energy storage, industrial motor drives, microgrids and electric vehicle powertrains. The PCS1000 is Hillcrest's newest product platform, currently in the A-sample prototype stage.

We seek Safe Harbor.