480 volt 3 phase with grounded B phase

[barstowporter]

Here we go.......


With a delta 480 volt utility supply, B phase is grounded. Would this not create a safety issue? Are my 3 phase motors (protected by standard 3 phase CB's) in a situation where the frames of the motors are now B phase?

Are not the frames of the motors B phase?

barstowporter

 

[iwire]

With a delta 480 volt utility supply, B phase is grounded. Would this not create a safety issue?

No, assuming the phase was intentionally grounded.

Are my 3 phase motors (protected by standard 3 phase CB's) in a situation where the frames of the motors are now B phase?

Yes

Are not the frames of the motors B phase?

Yes

But that B phase is grounded so B phase is as safe as a neutral in a wye system.

 

[barstowporter]

Thanks Iwire.....

Thanks Iwire.....

I assumed as much, but have not been exposed to it before here in Oregon.
We have 4 wire 480 volt w/ground systems, and then I found this 3 wire 480 system, which thru me a curve. SO...B phase is neutral (so to speak). They taped the feed to the WHM brown.

Thanks for the reply,



E= I x R ..........almost always applies....until you speak with certain physicists, trained in martial arts.

BarstowPorter

 

[barstowporter]

But...............

But...............

So now..............I'm floating in air, completely ungrounded........and I grab the motor frame (which is 480 volt B phase)........I feel nothing, because I am simply a bird on a wire, correct? No shock.....correct?



BP

 

[don_resqcapt19]

and I grab the motor frame (which is 480 volt B phase)....I feel nothing, because I am simply a bird on a wire, correct? No shock.....correct?

You feel nothing because there is no potential to earth or ground from the motor frame. The frame is connected to the EGC which is connected to the grounded conductor via the main bonding jumper at the service. This is exactly the same as with a 120/240 volt single phase system.
Don

 

[masterelect1]

Here We Go Again

Here We Go Again

Here we go.......


With a delta 480 volt utility supply, B phase is grounded. Would this not create a safety issue? Are my 3 phase motors (protected by standard 3 phase CB's) in a situation where the frames of the motors are now B phase?

Are not the frames of the motors B phase?

barstowporter

Another corner grounded delta system- may the mayhem begin

 

[iwire]

Another corner grounded delta system- may the mayhem begin

Don't just drop that, the opening poster is asking questions about the system and you throw a scare at him with no explanation.

So....what do you see as the problem?

Edited because my spelling is awful

 

[dbuckley]

I'd venture that a corner grounded system is much safer than an ungrounded system, becuase although Don notes in response to "and I grab the motor frame (which is 480 volt B phase)....I feel nothing, because I am simply a bird on a wire, correct? No shock.....correct?" that "You feel nothing because there is no potential to earth or ground from the motor frame" in my experience electricity leaks, and thus ungrounded isn't "totally isolated from ground" (and I'm using the term 'ground' loosly here, to mean, essentially, "you") but "connected to ground through some unpredictable resistance" and thus you can do a tingle from touching something ungrounded...

 

[infinity]

, and thus ungrounded isn't "totally isolated from ground"

Wouldn't this same phenomenon occur in a grounded system also, randomly opening the OCPD's?

 

[don_resqcapt19]

dbuckley,

in my experience electricity leaks, and thus ungrounded isn't "totally isolated from ground" (and I'm using the term 'ground' loosly here, to mean, essentially, "you") but "connected to ground through some unpredictable resistance" and thus you can do a tingle from touching something ungrounded...

But there should be nothing that you touch that is ungrounded. Even ungrounded sytems require EGCs and the first fault only creates a corner grounded system. It should not create a touch potential.
Don

 

[masterelect1]

Corner Grounded Systems

Corner Grounded Systems

Don't just drop that, the opening poster is asking questions about the system and you throw a scare at him with no explanation.

So....what do you see as the problem?

Edited because my spelling is awful

Recently and in the past there have been numerous posts/questions re: corner ground delta systems and the responses have been quite varied.

I pointed out that in industry it is quite common for an ungrounded delta secondary to allow continuous ops while the partial/total phase grnd. is located/eliminated asap. System also requires a ground detect monitoring sys.

There was also discussion re: the corner grnd having no beneficial purpose and again much discussion. Also, re: step/touch potential and again much discussion.

The 1st post was simply an on line attempt at humor as this subject has a storied past