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 Post subject: Solid State Overload Relays
PostPosted: Thu Jul 08, 2010 10:55 am 
Sparks Level

Joined: Tue May 18, 2010 7:03 am
Posts: 53
I am doing arc flash on a variety of sites. Many of the size 1 and 2 starters have solid state overload relays. The problem I'm having is it's close to impossible to find the right info for the right relay part number. If I do find it, it doesn't show up in the library of the software. A similar problem exists for circuit breakers that have electronic trips - a variety of rating plugs and control modules that can all be interchanged. These are mostly for motors in the 5 to 30 hp range. Is there another way to handle this that is fairly accurate but not so labor intensive as in driving up the cost?

I understand the need for accuracy but at what point does the level of detail get crazy?


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PostPosted: Thu Jul 08, 2010 11:13 am 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
mountaineer wrote:
I am doing arc flash on a variety of sites. Many of the size 1 and 2 starters have solid state overload relays. The problem I'm having is it's close to impossible to find the right info for the right relay part number. If I do find it, it doesn't show up in the library of the software. A similar problem exists for circuit breakers that have electronic trips - a variety of rating plugs and control modules that can all be interchanged. These are mostly for motors in the 5 to 30 hp range. Is there another way to handle this that is fairly accurate but not so labor intensive as in driving up the cost?

I understand the need for accuracy but at what point does the level of detail get crazy?


Motor overload relays do not react to short circuits and therefore are not normally included in arc flash studies.

Motor short circuit protective devices (either fuses or breakers) need to have accurate data if they are intended to be the devices that 'clear' an arc flash event.


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PostPosted: Thu Jul 22, 2010 5:29 am 
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Joined: Tue May 18, 2010 7:03 am
Posts: 53
:o sooooo, I have another basic beginner question now. What modules in the power analysis software use the motor overload/starter information? I'm doing load flow, short circuit, TCC and arc flash. Not doing cable sizing, ampacity, motor starting, transient analysis, etc.


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PostPosted: Thu Jul 22, 2010 6:08 am 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
mountaineer wrote:
:o sooooo, I have another basic beginner question now. What modules in the power analysis software use the motor overload/starter information? I'm doing load flow, short circuit, TCC and arc flash. Not doing cable sizing, ampacity, motor starting, transient analysis, etc.


They are used for protective device coordination. But, except for 200HP+ motors, I can't remember the last time I considered motor overload relays on 480V systems.


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