240volt and 3phase books

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dm9289

Industrial Maintenance Electrician
Location
Pennsylvania
Occupation
Industrial process repair/ maintenance Electrician
I have been around electricity for about 25yrs in CATV,Mass electronics production, Steel manufacturing, residential etc. I have hooked up many 240v and 3phase 480 devices succesfully, but I still feel I dont have a good grasp of how these things work. For example I dont understand current paths in 240v heating elements, For example in 120v I understand current flows from hot thru the element to the neutral. I dont understand when you put 240v on opposite sides of an element it doesnt just go boom.

So the long and short of this is can anyone recomend a text book to help me to understand these isssues from the basics on up?

Thanks
Dave
 
dm9289 said:
I have been around electricity for about 25yrs in CATV,Mass electronics production, Steel manufacturing, residential etc. I have hooked up many 240v and 3phase 480 devices succesfully, but I still feel I dont have a good grasp of how these things work. For example I dont understand current paths in 240v heating elements, For example in 120v I understand current flows from hot thru the element to the neutral. I dont understand when you put 240v on opposite sides of an element it doesnt just go boom.

So the long and short of this is can anyone recomend a text book to help me to understand these isssues from the basics on up?

Thanks
Dave
Click to expand...

Current flows from one conductor through the load to another conductor.
It is the load that keeps thing from 'going boom'. A 240V load is perfectly happy being connected to two wires that has 240V between them.
 
I thought that the 2 power sources would act against each other I guess it has something to do with how the transformer is set up. I understand that the load basically eliminates the short circuit
 
I'll be interested to see what people suggest myself. There are times I look at some of the things I hook up and wonder as well.
 
dm9289 said:
I thought that the 2 power sources would act against each other I guess it has something to do with how the transformer is set up. I understand that the load basically eliminates the short circuit
Click to expand...
You do not have 2 opposing power sources. You have either 1 source with a center tap (maybe 90% of utility transformers are this type) or you have 2 sources connected in series (maybe 90% of customer owned transformers are this type).
 
I need to get back to the basics with this. I can describe and understand most any DC or 120v fault, but 3 phase??? I understand how to hook it up I have done so succesfully many many times but I just dont get the theory and I need some heavy duty remedial training.
 
You described what happens half the time. The current goes the other way the other half of the time. Just double the voltage on the hot and you essentially get the 240 volt case. The only thing really special about the neutral is its relative voltage to some reference point.
 
Thanks I will continue to look thru this sire it seems valuable
 
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