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Rockwell Automation 1336T Wiring and Grounding Guide, (PWM) AC Drives User Manual

Page 52

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52

Rockwell Automation Publication DRIVES-IN001M-EN-P - March 2014

Chapter 3 Grounding

The grounding scheme can greatly affect the amount of noise and its impact on
sensitive equipment. The power scheme is likely to be one of these three types:

Ungrounded scheme

Scheme with high resistance ground

Fully grounded scheme

An ungrounded scheme (

Figure 16

) does not provide a direct path for the

common mode noise current, causing the current to seek other uncontrolled
paths. This causes related noise issues.

Figure 16 - Ungrounded Scheme

A scheme with a high resistance ground (

Figure 17

) provides a direct path for

common mode noise current, like a fully grounded scheme. Designers that are
concerned with minimizing ground fault currents commonly choose high
resistance ground schemes.

Figure 17 - Scheme with High Resistance Ground

A fully grounded scheme (

Figure 18

) provides a direct path for common mode

noise currents. The use of grounded neutral systems is recommended for these
reasons:

Controlled path for common mode noise current.

Consistent line-to-ground voltage reference that minimizes insulation
stress.

Accommodation for system surge protection schemes.

Earth Ground Potential

Earth Ground Potential