Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 646)

Section 13A
Connecting 8520 Digital Drive Systems
13A-12
Table 13A.A
Formulas for Determining Transformer Size
If you are using a machine tool application with: Use this formula to calculate the minimum transformer
KVA
Varying loads on the motor Number of Axes Machine Tool Duty
(Machine Tool Duty) 1 KW (Largest Motor) x 0.43 + 0.2
2 KW (Largest Motor) x 0.61 + 0.4
3 KW (Largest Motor) x 0.86 + 0.6
4 KW (Largest Motor) x 1.28 + 0.8
5 KW (Largest Motor) x 1.82 + 1.0
6 KW (Largest Motor) x 2.60 + 1.2
Constant acceleration and deceleration Number of Axes Rapid Accel/Decel Duty
(Rapid Accel/Decel Duty) 1 KW (Largest Motor) x 0.60 + 0.2
2 KW (Largest Motor) x 0.85 + 0.4
3 KW (Largest Motor) x 1.20 + 0.6
4 KW (Largest Motor) x 1.80 + 0.8
5 KW (Largest Motor) x 2.50 + 1.0
6 KW (Largest Motor) x 3.50 + 1.2
Motors that perform continuously at or near peak capacity Number of Axes Continuous Duty
(Continuous Duty) All KW (Total of All Motors) x 1.2 + 1.0
If you are using 8520 digital servo amplifiers, select a transformer from
this list of Allen-Bradley 1389 transformers. Base your selection on the
calculated minimum transformer KVA rating such that the selected
transformer’s KVA rating is equal to or larger than the calculated value:
Catalog Number Rating (KVA) Primary Voltage and Frequency
1389-T015DA 1.5 240/480V ac, 3 f 60Hz
1389-T035DA 3.5
1389-T050DA 5.0
1389-T100DA 10.0
1389-T125DA 12.5
1391-TA2 NEMA 1 Transformer Enclosure
The dimensions of the Allen-Bradley 1389 transformers are shown in
Figure 13A.8 and Figure 13A.9.