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APPENDIX 5E. ELECTROMAGNETIC INTERFERENCE

TABLE OF CONTENTS

5E.1 OVERVIEW ........................................................................................................................1

5E.2 DESCRIPTION....................................................................................................................1

5E.3 EMI-SENSITIVE APPLICATIONS ...................................................................................1

5E.4 REGULATIONS..................................................................................................................2

5E.5 REDUCTION AND MITIGATION ....................................................................................3

5E.6 CONCLUSION ....................................................................................................................4

LIST OF TABLES

Table 5E.1 Conducted EMI Requirements for Fluorescent Lamp Ballasts .....................................3
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APPENDIX 5E. ELECTROMAGNETIC INTERFERENCE

5E.1 OVERVIEW

In this appendix, DOE presents research regarding electromagnetic interference, or EMI, 

generated by electronic ballasts and possible methods to reduce these emissions. DOE also 

identifies specific applications that may be sensitive to the electromagnetic interference emitted 

by electronic ballasts. 

5E.2 DESCRIPTION

EMI can be defined as unwanted effects in an electrical system due to electromagnetic 

radiation and electromagnetic conduction from an external source. Electromagnetic radiation and 

electromagnetic conduction are differentiated by the way an electromagnetic field propagates. 

Conducted EMI is often the result of physical contact of the conductors, whereas radiated EMI is 

the result of electromagnetic induction from the external source to the affected electrical system. 

An EMI problem consists of a source, a coupling path, and an affected device. 

The source of EMI in a fluorescent lamp-and-ballast system consists mainly of switching 

components (transistors) in the ballast and the fluorescent lamp and lead wires. In highfrequency electronic ballasts, switching components create rapidly changing electric fields which 

can result in the generation of harmonic waves. These harmonic waves cause noise and voltage 

spikes, which can interfere with the function of other circuits on the line. Commercial electronic 

ballasts use switching components in the resonant inverter and power factor correction stages, 

while residential ballasts possess fewer switching components because they typically do not have 

a power factor correction stage. Low-frequency magnetic ballasts do not have switching 

components, dramatically reducing EMI generation. The second major source of EMI is the 

fluorescent lamp and ballast leads. The lamp and lead wires create a loop which in the presence 

of a rapidly switching AC waveform creates an antenna for radiated EMI. This phenomenon is 

more pronounced with electronic ballasts compared to magnetic ballasts.

Once the electric field is created, it must travel to the affected device to create 

interference. This can occur via conduction through the ballast into the building wiring or 

common ground connections to another device. EMI can also radiate via antennas or parasitic 

capacitances and inductances between conductors. EMI does not have to follow a strictly 

conducted or radiated path. For example, the radiated EMI generated by the lamp and lead wires 

can induce unwanted currents in the ballast itself which can then propagate through the building 

wiring to external devices. Finally, when EMI comes into contact with conductive material in the 

external device, it can induce currents that lead to device malfunction.

5E.3 EMI-SENSITIVE APPLICATIONS

DOE conducted research and interviews with fluorescent lamp ballast and fixture 

manufacturers to identify several applications as potentially sensitive to electromagnetic 

interference. These applications include, but are not limited to: medical operating room telemetry 

or life support systems; airport control systems; electronic test equipment; radio communication 
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devices; radio recording studios; correctional facilities; clean rooms; research laboratories; 

facilities with low signal to noise ratios; and aircraft hangers or other buildings with 

predominantly metal construction. These applications require ballasts that generate no or low 

levels of EMI.

5E.4 REGULATIONS

To understand the specifications that ballast consumers require for different applications, 

DOE researched existing regulations for EMI. DOE identified current standards for general 

applications such as commercial buildings, residential buildings, naval vessels, and other spaces. 

 The Federal Communications Commission (FCC) (47 CFR part 18) has standards which 

“regulate industrial, scientific, and medical equipment (ISM) that emits electromagnetic energy 

on frequencies within the radio frequency spectrum in order to prevent harmful interference to 

authorized radio communication services”. There are separate standards for consumer 

(residential) and non-consumer equipment and also for both radiated and conducted emissions. 

However, devices that operate at frequencies less than 1.705 megahertz (MHz), such as 

fluorescent lamp ballasts, are not required to report measurements of radiated emissions that 

exist at frequencies greater than 30 MHz. Because FCC regulations for the field strength of 

radiated emissions only exist for frequencies above 30 MHz, these standards do not apply to 

fluorescent lamp ballasts

 DOE also identified requirements for electromagnetic interference in Department of 

Defense MIL-STD-461Fa. The standards in section CE102 apply to conducted emissions from 

power leads between 10 kHz and 10 MHz while the standards in section RE102 apply to radiated 

emissions between 10kHz and 18GHz. These standards establish “interface and associated 

verification requirements for the control of the EMI emission and susceptibility characteristics of 

electronic, electrical, and electromechanical equipment and subsystems designed or procured for 

use by activities and agencies of the Department of Defense (DoD).” Table 5E.1 shows the 

existing FCC and military standards for conducted electromagnetic interference. The frequency 

column indicates the frequency of the electromagnetic interference rather than the frequency at 

which the ballast operates.

 The conducted EMI limits in MIL-STD-461F are given in units of decibel-microvolt 

(dBμV). Decibel-microvolt is converted to μV using the following formula:

Where A0 is the reference limit of 1 μV, LdB is the limit in dBμV, and A1 is the corresponding 

limit in μV. DOE converted the MIL-STD-461F limits for comparison to the FCC standards. 

 

a Department of Defense MIL-STD-461F is available at http://www.cvel.clemson.edu/pdf/MIL-STD-461F.pdf. Last 

accessed April 4, 2011.
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Table 5E.1 Conducted EMI Requirements for Fluorescent Lamp Ballasts

Frequency 

(MHz)

FCC Title 47 Part 18 conducted 

EMI, Maximum RF line voltage 

measured with a 50 uH/50 ohm 

LISN (μV)

Limit Level using CE 102 Test 

Procedure from Military 

Standard 461F, conducted 

emissions for all applications (μV)

Non-consumer equipment:

0.45 to 1.6 1,000 1,000

1.6 to 30 3,000 1,000*

Consumer equipment:

0.45 to 2.51 250 1,000

2.51 to 3.0 3,000 1,000

3.0 to 30 250 1,000*

*Applies up to 10 MHz

The first review of energy conservation standards for fluorescent lamp ballasts was 

completed in September 2000 (2000 Ballast Rule, 65 FR 56740). In that rulemaking, DOE

considered “the possibility of interference with certain equipment, such as medical monitoring 

equipment, caused by the high frequency of electronic ballasts.” The 2000 Ballast Rule therefore 

did not regulate T8 ballasts because of concerns that manufacturers would not be able to produce 

an electronic ballast that did not interfere with other equipment. It specifically stated that by not 

regulating T8 ballasts, magnetic T8 products could continue to be used in EMI-sensitive 

applications. 65 FR 56740, 56743 (September 19, 2000). 

5E.5 REDUCTION AND MITIGATION

EMI from magnetic ballasts (which operate at line frequency) has considerably lower 

intensity than EMI from electronic ballasts because EMI intensity is directly proportional to 

operating frequency. Furthermore, magnetic ballasts do not use switching components to 

increase the operating frequency of the lamp. Switching is a major contributor to EMI in 

electronic ballasts. Magnetic ballasts are frequently specified for EMI-sensitive applications, but 

are not likely to be able to meet efficiency levels proposed in this NOPR. DOE identified several 

means of reducing or mitigating EMI that could potentially be used in electronic fluorescent 

ballasts.

External EMI filters can be installed on the line side of an electronic ballast to limit 

unwanted conducted EMI from entering the building wiring. Additionally, a fixture can be 

designed with a grid lens or grounding cage to cover the lamp chamber in order to increase the 

impedance to a specific frequency and to bring radiated EMI to ground. Although ballasts do not 

have to meet FCC standards for radiated EMI, this type of EMI still presents a practical issue and 

fixture manufacturers must account for it. Because high frequency EMI has a very short 

wavelength, it can escape fixtures through very small openings, making high quality fixture 

design important. 

Measures can also be taken to limit the vulnerability of the sensitive external device to 

EMI. Shielding made of conductive material can mitigate the effects of EMI on susceptible 

equipment. The intensity of EMI decreases as it radiates outward from the source, so the risk to 

susceptible equipment decreases if it is placed farther from the EMI source. However, distance is 
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not always sufficient, and it is not always possible to design a layout that maintains a safe 

distance between fluorescent ballasts and EMI-sensitive equipment. 

5E.6 CONCLUSION

DOE learned from manufacturer interviews that magnetic ballasts are typically 

recommended for situations in which EMI has been or is expected to be a concern. 

Manufacturers indicated uncertainty over the effectiveness of these measures for each individual 

application. DOE was also unable to determine whether EMI related issues with electronic 

ballasts could be eliminated with the methods described above. Manufacturers suggested that an 

exemption for T8 magnetic ballasts would not constitute a risk for magnetic ballast substitution 

in current electronic ballast applications because magnetic ballasts are generally heavier, more 

expensive, and use more energy than electronic ballast alternatives. Customers generally prefer 

magnetic ballasts only in situations where EMI is a particular concern. 

Based on its analysis of EMI-sensitive ballast applications, DOE proposes that T8 

magnetic ballasts designed and labeled for use in EMI-sensitive environments only and shipped 

by the manufacturer in packages containing not more than 10 ballasts be exempt from the 

standards established in the NOPR. Because of the diversity in magnetic T8 ballast applications, 

DOE has designed the exemption similar to the previous fluorescent lamp ballast exemptions for 

replacement ballasts. DOE believes the exemption is necessary because in some environments, 

EMI can pose a serious safety concern that is best mitigated with magnetic ballast technology. 

DOE does not believe magnetic ballasts would likely be used as substitutes in current electronic 

ballast applications due to their higher cost and weight.