We are in the process of installing a ups system for GM. In the battery room the battery rack conductors come into a 1600 amp 3 pole main breaker before going through the breaker out to feed the ups. My question ,why is the L1 phase and the L2 phase series connected and then the positive line and load of the dc feeder connect to the two phases.
dc disconnect
- Thread starter timz
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- New Jersey
- Occupation
- Journeyman Electrician
Here is a wiring diagram from Sq D:
This would allow you to connect the batteries in either a 300 or 600 volt configuration. For a 480 volt system for example, this would allow you to wire strings of batteries in groups of less than 250 volts as required by 480.7.
This would allow you to connect the batteries in either a 300 or 600 volt configuration. For a 480 volt system for example, this would allow you to wire strings of batteries in groups of less than 250 volts as required by 480.7.
Keep in mind that an AC current goes through zero volts twice a cycle which allows the contact of a breaker to extinguish the arc as the contacts open a pass up through the arc chutes. Arc chutes break up the arc and cool it.
The, when one considers DC current there is always a voltage across the contacts. When the contacts open an arc is drown between them with the hope that when the contacts reach the maximum open position that the arc would be extinguished.
Now, take a look at your diagram. You will note that the contacts are connected in series, the contacts of which share the job of interrupting the DC current flow essentially tripling if 3 contacts were in series, the contact gap. With a 3p breaker the schemes that I am familiar with wired (2) poles of a 3p breaker in series feeding a DC load and the 3rd contact on the leg of the other side of the load.
Take a look at this instruction leaflet form a major breaker manufacturer.
http://www.eatonelectrical.com/unsecure/cms1/IL_29C702.PDF
The, when one considers DC current there is always a voltage across the contacts. When the contacts open an arc is drown between them with the hope that when the contacts reach the maximum open position that the arc would be extinguished.
Now, take a look at your diagram. You will note that the contacts are connected in series, the contacts of which share the job of interrupting the DC current flow essentially tripling if 3 contacts were in series, the contact gap. With a 3p breaker the schemes that I am familiar with wired (2) poles of a 3p breaker in series feeding a DC load and the 3rd contact on the leg of the other side of the load.
Take a look at this instruction leaflet form a major breaker manufacturer.
http://www.eatonelectrical.com/unsecure/cms1/IL_29C702.PDF
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Likewise, connecting relay contacts in series does more for increasing current-carrying (or more accurately, current-interrupting) capacity than does connecting them in parallel, which does, however, reduce contact resistance.
An engineer once told me that 4-section 2-pole main breakers, such as in the old GE panels, have two current-sensing sections and two parallel-contact "slave" sections that share current, but don't sense current; they're only switches.
An engineer once told me that 4-section 2-pole main breakers, such as in the old GE panels, have two current-sensing sections and two parallel-contact "slave" sections that share current, but don't sense current; they're only switches.
Trivia - Some Square D fused disconnects are listed for use on DC with only one pole breaking the current. I think it's limited to the 100A switch. It's the only one they bothered to have tested, mainly due to its use on home photovoltaic systems. Too many electricians were not wiring them correctly, so they had them retested using one pole.
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