Rockwell Automation Publication DRIVES-AT005D-EN-P - May 2022 47
Chapter 4 Non-regenerative Bus Supply Configuration
8. Perform the DC bus capacitance calculations in DC Bus Capacitance Calculation Method on page 87.
• The PowerFlex 750-Series internal DC bus capacitance data is taken from Table 9 on page 66
.
• The PowerFlex 755TM common bus inverter internal DC bus capacitance data is taken from Table 10 on page 68
.
• The Kinetix 5700 servo drive internal DC bus capacitance data is taken from Table 11 on page 69
.
• The PowerFlex 755TM non-regenerative bus supply internal capacitance data is taken from Table 13 on page 72
.
Verify that the µF/A ratio meets or exceeds the target of 40 µF/A ratio for this 480V AC system with mixed inverter types. This table
summarizes the DC bus capacitance data and calculations.
To meet the target µF/A ratio, it’s necessary to include one 30000 µF 2X capacitor bank within one of the PowerFlex 755TM non-regenerative
supply modules.
Sum the DC bus capacitance of the inverter/drives and non-regenerative supply. In this example, 71320 µF + 30000 µF = 101320 µF.
Sum the rated AC output current of the inverter/drives. In this example, 2354.0 A RMS.
The resulting DC bus capacitance to output amps ratio of 101320 µF / 2354.0 A RMS = 43.0 µF/A is greater than the target of 40 µF/A.
9. Verify that the PowerFlex 755TM non-regenerative bus supply is capable of precharging the total connected DC bus capacitance.
• The PowerFlex 750-Series internal DC bus capacitance data is taken from Table 9 on page 66
.
• The PowerFlex 755TM common bus inverter internal DC bus capacitance data is taken from Table 10 on page 68
.
• The Kinetix 5700 servo drive internal DC bus capacitance data is taken from Table 11 on page 69
.
• The PowerFlex 755TM non-regenerative bus supply maximum DC bus capacitance data is taken from Table 13 on page 72
.
The total connected DC bus capacitance is 101320 µF. Sum the PowerFlex 755TM non-regenerative module maximum DC bus capacitance
values for two (2X) modules. With a 0.2 second precharge ramp time, the total maximum DC bus capacitance is 150700 µF + 150700 µF =
301400 µF. This exceeds the total connected capacitance of 101320 µF; the PowerFlex 755TM non-regenerative bus supply precharge delay
time can be set to 0.2 seconds or higher.
The chosen PowerFlex 755TM non-regenerative bus supply is capable of precharging the total connected DC bus capacitance.
Section Name Drive Product Cat. No.
DC Bus Capacitance
(µF)
(1)
(1) See Appendix A for internal and maximum capacitance values.
Rated Output Amps Notes
Drive 1 PowerFlex F755TM 20G…D1K6 45000 1420 frame 10, HD
Drive 2 PowerFlex PF755 20G…D096 4500 77 frame 5, HD
Drive 3 PowerFlex 755TM 20G…D960 18000 800 frame 9, HD
Drive 4 PowerFlex 755 20G…D022 1020 14 frame 2, HD
Drive 5 Kinetix 5700 2198-S086
2198-CAPMOD
560
2240
43 ND, cluster capacitor module
Bus Supply PowerFlex 755TM
Non-regen
20JEH…D1K3
20JEH…D1K3
30000 2520 quantity of 2, 2X-modules
quantity of 1, 2X-cap bank
Max External Capacitance 301400
Additional Capacitance 0 µF
Total External Capacitance
(2)
(2) The calculated total external DC bus capacitance does not include the PowerFlex 755TM bus supply internal bus capacitance.
71320 µF
Total DC Bus Capacitance 101320 µF
Total Rated AC Output Amps
(3)
(3) The Total Rated Output Amps includes the external connected inverter/drive rated AC output amps. The bus supply rated amps aren’t included in this total sum.
2354.0 A RMS
This System target µF/A Ratio 40 µF/A
This system calculated µF/A Ratio 43.0 µF/A
µF/A ratio OK 0 µF additional required
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