Achieving Low Impedance Connections7 - Emerson E Series Installation Manual

Achieving Low Impedance Connections
Immunity can be improved and emissions reduced by maintaining the
components of the installation at the same ground potential. Establishing zero
potential difference between components requires a low impedance connection
between the components.
This can be achieved by bringing the conductive surfaces of the components
into direct contact. Over the short term this can be very effective. Over an
extended period of time, degradation of the connection may occur due to
corrosion. Corrosion can occur when a material reacts with the atmosphere or
when two dissimilar materials react with each other. Therefore component
materials should be conductive, compatible and exhibit good atmospheric
corrosion resistance.
Bringing components into direct contact cannot always be achieved. In these
situations a conductor must be relied upon to provide a low impedance path
between components. The impedance of the conductor is dependent on
conductivity and frequency. Conductors that provide a low impedance path at
low frequencies may not provide a low impedance path at higher frequencies.
A good rule of thumb to follow when specifying conductors for high frequency
applications is to use a metal strap with a length to width ratio that is less than
3:1.
A low impedance connection should exists between the following components,
but not limited to:
Enclosure and mounting plate
Servo amplifier chassis and mounting plate
EMI/RFI AC line filter chassis and mounting plate
Other interface equipment chassis and mounting plate
Other interface equipment chassis and electrical connectors
Enclosure and conduit fittings or electrical connectors
Enclosure mounting plate and earth ground
Motor chassis and conduit fittings or electrical connectors
Encoder chassis and electrical connector
Note: I t is critical that you keep the filter inputs routed away from any
electrical noise sources to prevent noise from being induced into
them and carried out of the enclosure.
Installation
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