Heating Device with Advanced Harmonics Control Enables Better Food Roasting

Shinpo Co., Ltd. has developed an innovative heating device and roaster that implements effective countermeasures against harmonics and flicker without degrading food roasting performance. The technology uses a control section managing duty cycle ratios with extended control cycles to deliver stable heating while minimizing electrical disturbances on power networks.

The Problem

Electric heating devices and roasters for cooking food have become increasingly prevalent as replacements for traditional gas burners. However, electric heaters consuming substantial amounts of AC power create significant challenges for electrical distribution networks. These devices generate harmonics and flicker that can disrupt the broader power system and affect other electrical equipment. While previous solutions attempted to address harmonics through phase angle control techniques that alter AC waveforms at higher frequencies, they often compromise heating performance, roasting consistency, or food quality.

The challenge requires implementing effective harmonics countermeasures while maintaining the roasting device’s ability to deliver consistent, high-quality heat for food preparation.

What This Invention Does

Shinpo’s heating device features a distinct separation between the heating section and control section. The heating section is driven by an AC power supply and contains the actual heating elements used for cooking food such as meat and vegetables. The control section manages a duty ratio, which is the ratio of energization time within a predetermined control cycle.

The key innovation is extending the control cycle to 15 seconds or longer. This extended cycle allows the control system to manage power delivery in a way that effectively reduces harmonics and flicker disruption while maintaining adequate heating performance. Rather than relying on high-frequency phase angle control or rapid on-off switching that degrades food roasting, the extended control cycle uses zero-crossing detection and synchronized switching techniques to maintain natural AC waveform patterns while controlling average power delivery.

Key Features

• Dual-Section Design. Separation of heating and control sections provides modular architecture and allows independent optimization of each function.
• Extended Control Cycle. The control cycle is 15 seconds or longer, enabling harmonics reduction without high-frequency switching disturbances.
• Duty Ratio Management. Variable duty ratio control adjusts the ratio of energization time within each control cycle to manage power delivery precisely.
• Zero-Crossing Detection. The control system detects AC power supply zero-crossing points to synchronize switching with natural waveform cycles.
• Harmonics Reduction. The extended cycle approach reduces electrical disturbances on power networks compared to traditional phase angle control methods.

Who Is Behind It?

Shinpo Co., Ltd., a Japanese heating equipment manufacturer, developed this innovation with inventor Yukio Kato. The patent was filed on 22 August 2025, claiming priority to Japanese Patent Application 2024-146043 filed on 27 August 2024. GLMR represents the application in Australia with offices in Sydney, New South Wales.

Why It Matters

This patent addresses a growing concern for electrical utilities and appliance manufacturers as electric heating devices proliferate globally. The development of roasting equipment that maintains high performance while reducing network disturbances represents important progress toward sustainable, grid-friendly appliances. The extended control cycle approach offers advantages over competing harmonics mitigation techniques by avoiding the performance compromises often associated with high-frequency switching methods.

As electrification of cooking and heating accelerates in residential and commercial settings, innovations that enable high-performance electric roasting without creating power quality problems become increasingly valuable for both consumers and electrical infrastructure operators.

Related Concepts

Electrical harmonics are voltage or current waveforms at integer multiples of the fundamental power frequency (50 or 60 Hz) caused by non-linear loads. High-power electric heating appliances can inject significant harmonic distortion into the distribution network, increasing conductor heating, causing interference in other equipment, and potentially violating grid connection standards set by electricity utilities.

Zero-crossing switching is a technique used in AC power control where circuit switching occurs at the instant the supply voltage or current passes through zero. This approach minimises electromagnetic interference and harmonic generation compared to phase angle control, which interrupts the waveform at arbitrary points and generates higher-frequency disturbances – a key advantage exploited by this invention’s extended control cycle design.

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AU 2025220812 was published in the Australian Official Journal of Patents on 19 March 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.