Article on the Discussions of the EMC Problems

The purpose of this article is to discuss the EMC problem and to briefly illustrate its relevance in the development, manufacturing and sale of commercial escalator components in Australia. The intent audiences of this report are engineers and managers from WTM, an escalator development company planning on entering the Australian market. Electromagnetic interference or EMI caused by radiation has been a known problem ever since the very earlier days of the electronic age. In some cases, electromagnetic interference can cause severe conflicts between electronic devices operating in the same environment. Today, with the rapid spread of electrical and electronic devices, electromagnetic compatibility (EMC) has become a subject gathering ever increasing interests and attention. Electromagnetic compatibility is known as the discipline of designing, analysing and testing of electronic equipment, to ensure that they are compatible with their electromagnetic environment. By conforming to the EMC regulations in the design stage, we reduce the potential of discovering design problem after the design has left the development laboratory. The definition of EMC can also be described using the terms EMI and EMS. MES is electromagnetic susceptibility or immunity. Thus, a electronic device must have an EMI emission below that of the defined maximum limit and must remain in fault-free operation with interference below the EMS limit. In a carefully controlled environment, such as in an airliner, passengers can be kept from using equipment which might cause interference with the airliners navigational and communication system. But this is not a realistic solution for an escalator system. The use of some electronic equipment in the close proximity of the elevator is inevitable and necessary. Hence, the main problem facing all elevator equipment developers is the need for sufficient equipment and component shielding thus preventing unwanted electromagnetic frequencies from entering or exiting devices and interfering with other control circuitry. This limits the unwanted electromagnetic radiation and ensures that components will continue to function in the presence of EMI from other electronic devices. To accomplish this, equipment designer and manufacturers must take reasonable precautions and be aware of the issues and regulations explained in the following section. In today†s world of electronics, it is necessary to deal with standards for electronic emission and susceptibility levels. The standards are guidelines for emission and susceptibility limits allowing electronic devices to coexist in the same environment. These standards are not static, as technology improves, new standards are established while existing standards are abolished. Manufacturers should refer to the suite of mandatory standards to determine the standards applying to the product. An escalator as a product comprises of many component parts, it is physically large and widely distributed. It is impossible to test a lift for compliance on site due to the fact that the test results are not reproducible. Thus, generic EMC standards are not appropriate. In this case product-specific standard which has been tailored to the specific circumstance and design of the product would apply and take precedence over generic standard. Normally, a product†s conformity has to be proof-read by a type test on EMI and EMS. The results must be within the allowed tolerances and must be independent from when and where it was performed. The EMC standards define the artificial interfaces, test equipment to be used and the set up of the test environment allowing reproducible measurements to be done on EMI and EMS. Developers should only use accredited ad trustworthy test laboratories for EMC tests. Once verification is complete, manufacturers is entitled to a Conformity Declaration. Each product must then be labelled according to the label specification. The label allows the origin of the product to be traced. In Australia and most other industrialise nations, devices without certification can not be sold. It is the responsibilities of the suppliers or manufacturers to ensure that all products on the market satisfy the technical requirement of the Australian EMC framework. Most of the time, a elevator comprises of components sourced from many manufacturers, in this case, the installer is considered the manufacturer. Thus, the components manufacturer must provide the installer with a declaration of conformity. Generally, the earlier EMC is taken into account during development, the lower the expense. From test cases, additional production costs fall between 1-5%. If the issue of EMC is considered after the development phase, the production costs can be significant higher. And if measures were taken after production, the costs will increase by another 30%. Apart from suffering lower profit, the entire manufacturing process will experience long delays, thus reduced market share. Due to high EMC test equipment cost, sometimes EMC measures are given to an external consultant. However, highest flexibility is achieved by doing pre-compliance testing and basic EMC measures in the company during development and give compliance testing and EMC fine tuning to the experts of EMC consultant. In any case, there should be at least one person in the company responsible for the management of EMC regulations, engineering and contacts to the consultants. For a product containing electric or electronic components, EMC is a quality feature just like others. Products without EMC certification do not have a standing ground on the Australia market. To be compliant with the Australian EMC regulations, work need to be carried out in every stage of the development cycle, from the design phase right through to the marketing and installation phase. Thus it is very important for TWM to consult the Australian Spectrum Management Agency of the Australian Communications Authority for a more concise reference for implementing measures which must be taken to assure that the products complies to the Australia EMC Standards.