Suggestion: Check Reference:
1. Fink D. G., Carroll J. M. "Standard Handbook for Electrical Engineers," 10th Edition, McGraw-Hill, Inc., 1968
pages 10-116 and 10-117, Section 429 "Flat Bars,"
Figure 10-165 (Reflects Amperes versus number of laminations per bus). It appears that your copper bars will fit the bus-bar arrangement L for 3000A
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Space 2 3/8"