Reducing Electromagnetic Interference (EMI)

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Article No: FAQ108

Nearly all electronic and electrical devices create some form of electromagnetic emissions. These emissions, when they are of high magnitude and particular frequencies, can interfere with the operation of other nearby electrical devices. Accordingly, most countries place regulations on various products in order to limit the magnitude of EMI emissions at certain frequencies.
The characteristics of an installation can amplify, focus, or channel electromagnetic waves in unpredictable ways, leading to unexpected results. Delta-Q Technologies provides the following guidelines for EMI reduction:

Wire Routing and Selection

• Keep wires away from emission-causing components and route them as directly as possible. Wires routed alongside emission-causing components pick up and conduct these emissions.
• Avoid loops in wiring. Loops act as antennas. The bigger the physical area of a loop, the greater the risk it will emit and/or pick up EMI.
• During testing, long cords, extension cords, and ground fault circuit interrupters (GFCIs) can detrimentally affect emissions. Most EMI regulations specify a minimum cord length for testing; shortening of wires to the minimum length in order to meet emission requirements is usually allowed. The regulations often allow shortening by trimming or by folding the cord back upon itself multiple times. Remember to avoid creating loops and do not coil the cord(s).
• Ensure the AC cord is of the correct type and gauge. Choosing the incorrect cord can adversely affect emissions.

Shielding and Grounding

• If wires must be routed near emission-causing components, shielding the wire reduces the severity of conduction. Regulations often allow the shielding to be connected to any point on the wire, but it is usually most effective when connected to a chassis or circuit ground point. Similarly, emissions from wires can often be contained by a grounded shield. Shields should usually be grounded at only one point, generally at the source of the signals in the wire(s).
• If the equipment has a metal frame, the emissions can be reduced by electrically connecting the chassis of the emission-causing component to the frame.

Filters and EMI Reducing Beads

• Install all emission-reducing devices required for each component of your system. Refer to the user manual provided by the manufacturer for each of these components. Many Delta-Q charger versions require emission-reducing components to be installed in/on the wiring harness.
• Filters can be added to reduce emissions. Inline filters for the AC input such as Epcos B84112G0000B110, Schaffner FN2030-10-06, and Delta 10DSCG5 have been found to be effective in many cases. Be sure to select a filter designed for the application and one that meets local requirements.
• The IC, ICL, and RC Series chargers are tested for worst-case radiated emissions by using a fully populated (12/14) wires on the Signals and Control connector. An EMI reducing bead is installed over all wires connected to the Signals & Control connector to meet the requirements of radiated emission. However, it is recommended to determine whether the ferrite bead is required or not in the end application while performing Electromagnetic Compatibility (EMC) testing on the entire system/vehicle. There is a good chance the ferrite bead may be reduced (in size) or not be required in cases where only a few wires are used on the Signals and Control connector, or where the signal wires are shielded or partially shielded by the application’s housing/chassis.

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