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 Post subject: inverter question
PostPosted: Fri Feb 27, 2015 10:08 am 

Joined: Fri Feb 27, 2015 10:02 am
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One of my clients needs to do some commissioning on an inverter box that has 480V AC (28kW) coming in and 1000V DC going out. There is no arc flash assessment done as far as he knows. My client is asking me what PPE they need to wear to commissioning these inverters. I can't seem to find anything in 70E tables that makes sense. Any ideas? Thanks in advance.


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 Post subject: Re: inverter question
PostPosted: Fri Feb 27, 2015 11:58 am 
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Joined: Tue Oct 26, 2010 9:08 am
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Location: North Carolina
bruinfan1979 wrote:
One of my clients needs to do some commissioning on an inverter box that has 480V AC (28kW) coming in and 1000V DC going out. There is no arc flash assessment done as far as he knows. My client is asking me what PPE they need to wear to commissioning these inverters. I can't seem to find anything in 70E tables that makes sense. Any ideas? Thanks in advance.


1. You need to know the electrical characteristics of the incoming side of things. Protection on the AC side is provided by the overcurrent protection device on the incoming side as far as how quickly a fault clears. The amount of energy is determined by fault current, NOT normal operating current. Depending on the wiring, transformer, and upstream equipment, this can vary widely. There is no hard and fast rule here. In addition if the drive is regenerative then during a fault it can regenerate, putting additional energy into the fault from the load side. This needs to be accounted for in a power system study.
2. Similar to #1, on the load (DC bus) side, you need to gather the same information (fault current, overcurrent protection opening time, voltage) and use say the model developed by Doan or Ammerman to estimate it, or else go by test data available. Unlike the first case where an actual standard exists (IEEE 1584), this relies on theoretical models or actual test work.


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 Post subject: Re: inverter question
PostPosted: Mon Mar 02, 2015 7:36 am 
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Joined: Fri Apr 15, 2011 7:43 am
Posts: 177
Location: Colorado
There is also some new information about DC when capacitors are involved. Many times inverters may use capacitors. There has not been a lot of research done but the incident energy levels may be significantly higher. I do not intend to make you job more difficult but being the best informed is always good.

Do some research on the electrical safety workshop.


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