94 Rockwell Automation Publication DRIVES-AT005D-EN-P - May 2022
Appendix A Electrical Ratings, Recommended Protective Devices, and DC Bus Capacitance
Example Four DC Bus Capacitance Calculation
Machine Characteristics
Attribute Value
System Voltage 400V AC
Duty Rating Normal Duty (ND)
Inverter/Drive Products Mixed; PowerFlex 750, PowerFlex 755TM
Drive and System Data
Drive # Product Family Cat. No.
Frame
Size
AC Output
Amps RMS
(1)
(1) Data obtained from Appendix A.
Internal DC Bus
Capacitance (µF)
(1)
1 PowerFlex 755TM 20G1D3C540 8 540 9000
2 PowerFlex 755 20G11NC015 2 15.4 705
Totals 555.4 9705
Bus Supply PowerFlex 755TM Regenerative Bus Supply 20JxF…C540 8 – 9000
External Capacitance 0
Total 18705
Additional Capacitance Calculations
Target µF/A Ratio 40 µF/A 400/480V AC
Calculated µF/A Ratio 33.7 µF/A
Additional Capacitance Required 3511 µF Additional Capacitance Required
Sample Bill of Material
Cat. No. Qty. Description
PN-50085 or ER-101011 1 Ground Fault Indicator Filter
20J1F3C540LNDNNNNN-P50 1
PowerFlex 755T Bus Supplies, Air Cooled, Regenerative & Low Harmonic Bus Supply (PowerFlex 755TM), Type 1/IP21, Floor Mount, LD -
364 kW (628 A), ND - 336 kW (579 A), HD - 286 kW (494 A), 400V AC, 3 PH, Frame 8, Standard EMI Protection, Door Mounted HIM (20-750-
C6S) & TotalFORCE® Control
20G1D3C540MNDNNNNN-C11 1
PowerFlex 755T Drives, Air Cooled, Common Bus Inverter with DC Precharge (PowerFlex 755TM), Type 1/IP21, Floor Mount, LD - 315 kW
(585 A), ND - 315 kW (540 A), HD - 250 kW (460 A), 400V AC, 3 PH, Frame 8, Standard EMI Protection & Reflected Wave (dV/dT) Filtering,
Door Mounted HIM (20-750-C6S) & TotalFORCE Control
20G11NC015AA0NNNNN 1
PowerFlex 755 AC Drive, with Embedded EtherNet/IP, Air Cooled, AC Input with DC Terminals, Open Type, 15.4 Amps, 7.5 kW ND, 5.5 kW
HD, 400V AC, 3 PH, Frame 2, Filtered, CM Jumper Removed, DB Transistor, Blank (No HIM)
HSJ25 2 600VAC 25 A Class J HS Fuse
1321-M048 1 Common Mode Choke, 45 A, Open Style
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