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Due to the high working frequency, the induction cooker may interfere with other household appliances. In this regard, electromagnetic compatibility has become an important indicator to judge whether the induction cooker causes interference to other electrical appliances. This also reflects the safety of induction cooker to a certain extent.

With the popularity of the concept of cooking without fire, induction cooker has gradually become the standard configuration of electrical appliances in the family. In autumn and winter, induction cooker is a common tool for hot pot. However, although the induction cooker has the advantages of fast heating, no open flame, convenient cleaning and so on, its safety and energy consumption make consumers worried. In the past, there were many problems in these two aspects in some sampling inspections by government departments.

Which induction cooker is safer, more efficient and energy-saving? In September 2014, consumer report purchased five popular household induction cooker brands from e-commerce platforms such as jd.com and Suning, including Midea, Supor (15.07, 0.10, 0.67%), Jiuyang, Galanz and Pentium, for comparative evalsuation. From the perspective of safety and energy efficiency in consumers’ daily use, the test indicators include thermal efficiency, standby power consumption, electromagnetic radiation, disturbance voltage, adaptability to high and low temperature and high humidity environments, etc.

In terms of safety indicators, the test results of the third-party authority showed that the electromagnetic radiation of the five induction cookers met the national standard limits; However, in the test of “disturbance voltage”, five products were “completely destroyed”.

5. The disturbance voltage of famous brands does not meet the standard

For kitchen appliances, safety is always put in the first place by consumers.

The working principle of the induction cooker is to convert electric energy into heat energy in the vessel through the change of magnetic field. However, because its power is usually large, its working frequency is also higher than that of ordinary household appliances. Because of this, consumers are usually very concerned about whether their electromagnetic radiation poses a threat to them. Due to the high working frequency, the induction cooker may interfere with other household appliances. In this regard, electromagnetic compatibility has become an important indicator to judge whether the induction cooker causes interference to other electrical appliances. This also reflects the safety of induction cooker to a certain extent.

With reference to gb4824-2004 measurement methods and limits of electromagnetic disturbance characteristics of industrial, scientific and medical (ISM) RF equipment (hereinafter referred to as gb4824-2004), this journal tested the electromagnetic radiation and disturbance voltage of five induction cookers.

Induction cooker inspection

The test results show that the electromagnetic radiation of the five induction cookers is within the standard limits. This shows that this problem was taken into account in the design of these five induction cooker, so that part of its electromagnetic radiation will be discharged from the induction cooker body and the pot body. In addition, the amount of radiation of the induction cooker has a very important relationship with the power, quality and the pot used by the induction cooker.

However, the test results of continuous disturbance voltage show that the five induction cookers are not up to standard. That is, according to the detection requirements of gb4824-2004, the quasi peak and average values of the five tested products measured at different test frequencies partially exceed the limits in the standard. In the quasi peak test results, the test values of Galanz and Jiuyang in the specific test frequency band exceed the standard limit more; The test results of the average value show that the test values of Midea and Jiuyang in different test frequency bands exceed the standard more.

Electromagnetic furnace test report I: electromagnetic compatibility is not up to standard

In this regard, Ke Yixuan, deputy director of the electrical safety laboratory of Guangdong entry exit inspection and Quarantine Technology Center, explained to the reporter of consumer report that the disturbance voltage is a kind of electromagnetic disturbance. If the disturbance voltage exceeds the limit, it will cause interference to the electrical appliances with the same frequency range in the region and make other electrical equipment malfunction. If it is widely used, the continuous disturbance voltage is too large, which will also have a certain impact on human body.

The problem of unqualified disturbance voltage of induction cooker has always existed. In 2008, the product quality supervision and inspection center of Guangdong Province sampled 30 induction cooker products on the market, and the results showed that the qualified rate of disturbance voltage was 0. Zhong Yuansheng, the Engineer in charge of this project, analyzed that the key reason for the unqualified disturbance voltage is related to its design principle. When the induction cooker works, the mains power (50/60hz) is changed into a high-frequency voltage of 20-40khz, which will cause greater disturbance in the frequency band of 20-40khz. If effective EMC measures are not taken, the frequency will exceed the limit at a certain point in the frequency range.

Mandatory standards for dislocations

An important reason for the “military failure” in the disturbance voltage index is related to the connection and dislocations between the current two national mandatory standards for induction cooker.

Gb4824-2004 referred to in this inspection is a national mandatory standard. Induction cooker also needs to pass CCC certification (compulsory product certification system, namely 3C certification), but electromagnetic compatibility testing is not included in the latter, which leads to the neglect of this performance by manufacturers.

Our reporter learned from the national certification and accreditation administration that the current 3C certification implementation standard for household induction cooker is cnca-01c-016:2007 implementation rules for compulsory certification of electronic and electrical products household and similar purpose equipment. Under this standard, there are no specified requirements for electromagnetic compatibility items of induction cooker. When the manufacturer certifies the quality of Induction Cooker products, electromagnetic compatibility does not need to enforce the aforementioned gb4824-2004 standard. Similarly, there are kitchen appliances such as microwave ovens and electric ovens.

In the view of third-party testing institutions, the electromagnetic compatibility of induction cooker is more important than other household appliances, but for the reason why this indicator is not included in the 3C compulsory certification project, our reporter received a very vague reply from the China Quality Certification Center. Some respondents said that they did not understand the formulation of standards, but only certified products according to regulations.

Zhong Yuansheng believes that the unqualified electromagnetic compatibility is related to the design and material of the product. Generally, if the disturbance voltage of the induction cooker meets the standard, it can be achieved by means of circuit design and adding filter circuit, but this needs to be improved in the quality and quantity of parts, and the production cost will increase accordingly.

At present, although the electromagnetic furnaces sold in mainland China do not enforce the relevant standards of electromagnetic compatibility projects, they are relatively strict in the export field. In June this year, a batch of 4805 induction cooker products with a value of more than 80000 US dollars in Shunde, Guangdong Province were notified by Taiwan because of the safety risks caused by unqualified electromagnetic compatibility projects. Guangdong Shunde Inspection and Quarantine Bureau said that the main reason why this batch of induction cooker was notified was that the radiation interference level did not comply with the provisions of Taiwan standard cn s13803 “limits and measurement method of interference characteristics of industrial, scientific and medical RF equipment”.