The electromagnetic compatibility (EMC) design of commercial induction cookers needs to address two core issues: harmonic interference suppression and excessive radiation control. A systematic approach is needed to ensure stable operation of the equipment in complex electromagnetic environments. Harmonic interference primarily originates from the high-frequency switching actions of power electronic devices, causing distortion of the grid current waveform. Excessive radiation is closely related to high-frequency electromagnetic leakage from the coil and power circuits. Both can lead to equipment performance degradation, malfunctions of surrounding electrical appliances, and even personal safety hazards. Therefore, a multi-dimensional design approach is necessary to address these issues.
For harmonic interference, commercial induction cookers typically employ a strategy combining passive filtering and active compensation. At the power input, an LC filter is the core component for harmonic suppression. Its low-pass network composed of inductors and capacitors effectively filters out high-frequency switching noise, preventing harmonics from being injected into the grid. For high-power equipment, a reactor is connected in series before the filter capacitor to avoid the amplification effect of the capacitor on specific frequency harmonics. Furthermore, active power filters (APFs) are increasingly widely used. They dynamically cancel harmonics by monitoring the harmonic components in the grid current in real time and generating reverse compensation current. This technology is highly adaptable to harmonics with varying frequencies and amplitudes, achieving compensation efficiencies exceeding 90%, making it particularly suitable for scenarios with large fluctuations in grid impedance.
Controlling excessive radiation requires addressing both source suppression and propagation path blocking. As the primary radiation source, the coil design needs to optimize magnetic field distribution uniformity and reduce leakage caused by excessively high local magnetic flux density. Employing multi-layer composite coil structures and adjusting turn spacing and interlayer insulation materials can reduce the edge diffusion effect of high-frequency electromagnetic fields. Simultaneously, the layout of power circuits must adhere to the principle of "separation of strong and weak currents," physically isolating high-frequency switching devices (such as IGBTs) from control circuits and blocking spatial coupling by adding shielding covers or conductive coatings. For the chassis structure, using high-permeability materials for the shielding layer can effectively absorb low-frequency magnetic fields, while high-frequency radiation needs to be attenuated through metallization or conductive sealing strips.
Electromagnetic compatibility design also needs to consider the interaction between the equipment and the external environment. On the grid side, the combination of automatic air switches and fuses can prevent overcurrent surges caused by voltage fluctuations and protect filter circuits from damage. To mitigate interference between devices, the cumulative effect of high-frequency radiation can be avoided by properly planning installation spacing (e.g., maintaining a distance of more than 1 meter from televisions and microwave ovens). Furthermore, choosing products that have passed 3C certification and electromagnetic compatibility testing, and prioritizing models with radiation values lower than international standards (e.g., ≤100μT), can reduce radiation risks at the source.
Software algorithm optimization plays a supporting role in improving electromagnetic compatibility. For example, using soft-switching technologies (such as ZVS and ZCS) can reduce the di/dt at the moment of IGBT turn-on, thereby reducing electromagnetic noise caused by voltage spikes. Adjusting power regulation strategies avoids resource waste caused by the device continuing to operate at full power when the cookware temperature has reached the set value under constant power control mode, indirectly reducing the number of high-frequency switching operations and lowering the cumulative radiation effect.
Testing and verification are crucial aspects of electromagnetic compatibility design. Radiated emission (RE) and conducted emission (CE) tests should be conducted on the equipment in a semi-anechoic chamber to simulate actual usage scenarios and ensure compliance with international standards such as IEC 61000. For frequencies exceeding the standard, interference sources must be located through spectrum analysis, and filtering parameters or shielding structures adjusted accordingly. Furthermore, long-term operational testing verifies the electromagnetic stability of the equipment under conditions of temperature changes and load fluctuations, preventing a decrease in shielding effectiveness due to material thermal expansion and contraction.
The electromagnetic compatibility design of a commercial induction cooker is a complex systems engineering project involving multiple disciplines such as power electronics, electromagnetic field theory, and materials science. Through the comprehensive application of harmonic filtering, radiation shielding, circuit optimization, algorithm improvement, and rigorous testing, a balance can be achieved between efficient heating and low electromagnetic pollution, meeting the stringent requirements of reliability, safety, and environmental protection in commercial applications.
