Specification

2700DB0202R03/12 Corner-Grounded Delta (Grounded B Phase) Systems
09/2012 Application
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5
ENGLISH
Application Schneider Electric has tested and obtained a UL listing for equipment to be
used on grounded B phase systems. The “Devices” section below lists
devices on unassembled and factory assembled distribution equipment that is
suitable for such use. It is recommended to provide some type of equipment
ground fault protection when the equipment is used on grounded B phase
systems, due to the potential high fault currents on the first ground fault.
Because of the special requirements, when ordering factory assembled
equipment for use on grounded B phase systems, the order should be
clearly identified as such on the order entry paperwork. Merchandised
equipment must be properly selected and ordered from the Digest.
It is also recommended for engineers to specify that equipment is
UL-labeled as suitable for use on grounded B phase systems, when
applicable.
Devices NOTE: All equipment listed in this document is rated for use on systems
with a grounded B phase.
BP Fusible Switches BP switches can be used on corner-grounded delta systems in manually or
electrically operated, upright or inverted mount, and 2- or 3-pole versions.
3-pole switches have a copper link inserted in the center phase to restrict
insertion of a fuse into the grounded conductor.
The short-circuit current rating of BP switches on this system is 200,000
ampere interrupting rating (AIR) with Class L fuses installed.
QMB and QMJ Switches Table 3 lists QMB and QMJ switches that are UL Listed in File E34358, Vol. 2,
Section 1 for grounded B phase systems. 2- and 3-pole switches listed in Table
3 are rated for grounded B phase. However, only 2-pole switches are marked to
indicate a grounded B phase rating. The short-circuit current rating for 30–200
A Series E1 switches is 200,000 AIR. The short-circuit current rating for Series
E1 400–800 A switches is 50,000 AIR.
Table 2: BP Switches
BP Switch Ampere
Rating
Grounded B Phase
System Rated
Maximum Grounded B
Phase Voltage
1
1
For 240 V grounded B phase systems, use only 480 V BP switches listed in the table above.
800
Yes 480 Vac
1200
1600
2000
2500
Table 3: QMB and QMJ Switches
QMB/QMJ
Switch
Series
QMB/QMJ
Switch
Ampere
Rating
Grounded B Phase Rated
Main
Switch
Branch
Switch
240 Vac
Unit
480 Vac
Unit
Two-
pole
Three-
pole
1
1
3-pole switches have a copper link inserted in the center phase to restrict insertion of a fuse into the
grounded conductor. The rating is not shown on the wiring diagram of 3-pole switches.
E1
30
N/A
Yes Yes Yes
Yes
Yes
60
100
Yes
200
400
600
800 N/A