Electromagnetic compatibility (EMC) is the ability of electrical/electronic equipment to operate without being caused or affected by electromagnetic interference (EMI) in its installation environment. EMI refers to interference that affects equipment operation due to irregular energy entering the equipment through wiring connections or electromagnetic radiation. Radiated EMI is also known as radio frequency interference (RFI). Conducted EMI is also known as high-frequency noise. In the United States, there are no specific and comprehensive regulations or standards covering the EMC of variable frequency drives (AFDs). FCC Standards: Part 15 of the Federal Communications Commission (FCC) standard applies to unauthorized equipment that radiates radio frequency energy. FCC Part 15 applies to all variable frequency drives because it is classified as radiant equipment. All equipment covered by Part 15 must operate under the general operating conditions set forth in Section 15.5. The purpose of Section 15.5 is to require that the equipment not interfere with any legally operating broadcast, navigation, or security service and must be accommodating any interference caused by other equipment. According to Section 15.13, manufacturers of radiant equipment should employ good engineering practices to minimize the risk of harmful interference. FCC 15 applies to microprocessor-controlled variable frequency drives because they are classified as digital devices. Variable frequency drives, as commercial or industrial equipment, are an exception and are only subject to the general operating conditions specified in Section 15.5 (described above)... Nevertheless, the Federal Communications Commission (FCC) strongly recommends that manufacturers of these special devices strive to meet the technical standards of FCC 15. FCC 15 limits the radio frequency voltages transmitted from digital devices to utility power lines in the range of 0.15 to 30 MHz. FCC 15 also limits the magnetic field strength radiated by digital devices in the range of 30 MHz and above. Voltages transmitted to power lines at frequencies below the FCC-specified frequencies are considered harmonic distortion voltages. Harmonic distortion is defined in the IEEE 519 standard. Evaluating the drive as a digital device under FCC 15 suggests that the microprocessor of the drive is unlikely to be a significant source of electromagnetic interference (EMI). The most significant potential source of EMI and RF interference for the drive is the power switching circuitry. This potential source is largely independent of the microprocessor design or other types of control circuitry. EMI generated in the device is caused by the AC output waveform formed by the switching of positive and negative terminals at the DC bus output. Each output switching operation causes the terminal voltage (for a 480-volt driver) to jump from 650 volts on one terminal to 650 volts on the opposite terminal. This instantaneous voltage change can potentially generate significant amounts of radio frequency energy. However, when evaluating the driver as a microprocessor-controlled digital device, it is not the most significant source of electromagnetic interference (EMI). Drivers seeking to meet FCC standards are often labeled as FCC 15 compliant due to the lack of clearly defined and stringent application regulations. While drivers must meet FCC 15 requirements for transmission and radiation standards for Class A or Class B digital devices, FCC 15 does not include or specify test methods designed for drivers. Without specified test methods, any claim of driver compliance is questionable. The FCC 15 standard regarding transmission and radiation was revised in 2002 by the International Electrotechnical Commission (IEC) International Special Committee on Radio Interference (CISPR) (see FCC 02-157) to harmonize domestic requirements for compliance. CISPR 11 provides a method for testing driver compliance with these standards. The radiation standards set by CISPR 12 are lower than those of FCC 15. Therefore, FCC 15.109 was added to FCC 15 in 2003. Sections a and b of this section mention optional radiation standards; digital devices should comply with CISPR 22 (1997) (see FCCDA 03-3848). CISPR 22 is for digital devices, while CISPR 11 covers industrial, scientific, and medical devices. The US Food and Drug Administration encourages manufacturers of medical electronic devices to adopt CISPR 11. The European Commission directs the development of different standards for various products within the European Economic Community. Many of these standards originate from those developed by the IEC. The EMC product standard for electric drive systems—EN 61800-3 (or IEC 61800-3)—is the main standard for variable speed drives. This standard's testing methods include test procedures and details, are particularly suitable for drives, and are quite comprehensive. It covers electromagnetic radiation and radiation immunity of drives. IEC 61800-3 defines two installation environments: the first environment includes residential buildings. It also includes facilities that are directly connected to the low-voltage power supply network supplying power to residential buildings without passing through an intermediate transformer. The second environment includes all facilities except those directly connected to the low-voltage power supply network supplying power to residential buildings. IEC 61800-3 sets out sales plans for two types of users: Unrestricted Sales: Unrestricted sales refer to a sales model where the supply of equipment is independent of the customer's or user's electromagnetic compatibility (EMC) capability. Restricted Sales: Restricted sales refer to a sales model where the manufacturer restricts the supply of equipment to individuals or groups who possess the technical capability regarding the EMC of the equipment. The drive must be installed according to the instructions in the installation manual. Other Information: Other information can be found in two ABB publications: - Technical Guideline No. 2, European Commission Directives on Requirements and Speed-Regulating Electric Drive Systems - Technical Guideline No. 3, Recommendations for EMC-Compliant Installation and Configuration in Electric Drive Systems. Drives with the most comprehensive EMC should meet the IEC 61800-3 EMC and radiation standards, be sold under restrictions, and be installed in the first environment. The manual must include instructions for installing the drive to comply with radiation standards. Drives that comply with the above requirements generally meet the technical requirements of FCC 15, including radiation standards for Class A digital devices.