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Keeping up with the requirements of the Code should be the goal of
everyone involved in electrical safety. Following is what I feel is an
important rule in the 2020 NEC®, complete with
graphics and a video. I encourage you to use it as a training resource for
your organization, and share it with your colleagues.
| Adjustable Speed Drives - Article 430 |
The content below is extracted from
Mike Holt's Electrical Exam Preparation textbook, based on the 2020 NEC.
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Sometimes you need more control of a motor than just on-off and adjustable speed drives allow for such control and to a degree of which is nothing short of amazing! Adjustable-speed drives can be variable-frequency speed drives (VFDs)—which refer to alternating-current drives only, or variable-speed drives (VSDs) which can be alternating-current or direct-current drives. The branch or feeder circuit runs through the adjustable-speed drive which in turn controls the speed of the motor(s) served. Do you know how to size these branch or feeder circuit conductors? How about the overcurrent protection device rating? Do we use the table values in the NEC based on the horsepower of the motor?
If you’re studying for an exam, or you just don’t know or aren’t quite sure of the Code requirements for sizing these conductors [430.122] or the overcurrent protection for these circuits [430.130] you need to watch this video where these rules and overall concepts of adjustable speed drives are explained (in great detail by myself and a panel of experts) and review the included text, graphics, and example calculations. Doing so will help to ensure that you apply these rules confidently and accurately!
 Click here or on the thumbnail to the left to view or download the PDF of this rule to follow as you watch the video. (3 page, 254 KB)
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Click on the image above to watch the video
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We'd
love to hear from you about this series, and the ways you're using it.
Send us your comments and feedback by clicking on Post a Comment
below. Look out for the next part in this series a month from now, and
please share with your colleagues.
This content is extracted from Mike Holt's Illustrated Guide to
Electrical Exam Preparation, based on the
2020 NEC Program.
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