by May 10, 2001 0 comments

The importance of controlling EMI (Electromagnetic Interference) was recognized in the early days of radio communication when it was observed that electrical equipment could significantly interfere with radio reception. The first attempts to control EMI were made in the 1930’s, and by 1939, the first preliminary EMI standards had been evolved. After the invention of the transistor in 1948, the use of electronic equipment grew very rapidly and the necessity of more stringent control of EMI became evident to the electrical engineering community. It was also recognized that the typical electronic equipment could be disturbed by adjoining electrical equipment; and at the same time also disturb other electronic equipment. Therefore, the more general term of EMC (Electromagnetic Compatibility), which incorporates both these aspects, has come into use. Today, there are a large number of EMC compliance standards that electrical and electronic equipment must comply with. Such compliance is essential for equipment intended for sale in the world market.

Test Facility

In view of the fast track changes in
the IEC standards, the standardization testing and quality certification
(STQC) directorate under Ministry of Information Technology is equipped
with all facilities at major laboratories located at Delhi, Mumbai,
Bangalore and Kolkatta. The laboratories are helping the manufacturers
by providing test facilities at nominal cost as well as development
assistance to improve the product for complying with EMC requirements.
STQC has also taken initiative to introduce EMC compliance certification
scheme based on international standards like IEC and EN for the benefit
of Indian manufacturers to put EMC mark on their product as well as provide a route to CE marking. Already many UPS manufacturers are utilizing these services to improve product quality. Hopefully all UPS vendors will take benefit from these facilities.

The UPS is increasingly a part of electrical and electronics requirements. A variety of UPSs are available to fulfill the customer’s demand for continuity and quality of power for different types of loads over a wide range of power from less than 100 W to several MW. With globalization, Indian manufacturers face stiff competition not only in product quality but also in competitive advantage. In addition to electrical specification for a UPS, the safety parameters and EMC compliance are essential to compete with global brands and in export trade. The CE marking is mandatory for this product to sell in the European market. 

EMC requirements for UPSs

The Electromagnetic Compatibility (EMC) requirements for UPSs are laid out in the following IEC (International Electrotechnical Commission) standards. 

EIC 62040-2: UPS Part-2–EMC requirements
IEC 62040-3: UPS Part-3–Method of specifying the

performance and test requirements

IEC 62040-2 specifies the following:

  • EMC requirements
  • Test methods
  • Minimum performance levels

Typically, UPSs are subjected to the following tests:

  • Conducted Emission (CE): Frequency 0.15—30 MHz
  • Radiated Emission (RE): Frequency 30—1000 MHz
  • Input-Current Harmonics: As per IEC 61000: 3—2 
  • Radiated Immunity: As per IEC 61000 4—3 
  • Electrical Fast Transient: As per IEC 61000 4—4 
  • Low Frequency signal test: 140 —360 Hz at 10V amplitude 
  • Electrostatic Discharge: Contact/Air discharge

EMC test engineers verify that the standards are met under all operating conditions within the specifications of the equipment. In case of failure to comply with the standards, test engineers perform an EMC audit to suggest remedies to the equipment manufacturers. Generally, these remedies may consist of:

  • Incorporation of a filter to comply with CE requirements
  • Use of active power factor correction or filter for reduction in current harmonics
  • Use of correct wiring, grounding and bending practices for reduction of radiated emission, and ability to withstand EFT and ESD tests

The UPS is a combination of converters, rectifiers, switches and batteries. The technology is constantly changing and the manufacturers are adopting newer techniques for reduction of size, cost, and easy maintenance. The majority of UPS load equipment such as computers employ power supplies that present a non-linear load to the UPS and can be tolerant of non-sinusoidal voltage waveforms for limited time duration. UPS output ratings are specified to be compatible with non-linear loading and linear loading.

Though no mandatory EMC requirement exists in India, global brands with CE, UL, CSA, and VDE markings will have a competitive edge over others. Once EMC compliance is made mandatory in India, local manufacturers will have to spend huge money and time for meeting these requirements. Hence, it would be in the interest of vendors to understand EMC requirements and have their products evaluated at an independent test laboratory at the earliest.

Dr A K Agarwala  
IDDC Labs, Indian Institute of Technology A Sathyanarayanan
Additional Director, 
Electronic Regional Test Laboratory New Delhi 110020

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