Rockwell Automation Publication DRIVES-AT005D-EN-P - May 2022 43
Chapter 4 Non-regenerative Bus Supply Configuration
Example Basic Sizing of the Non-Regenerative Bus Supply
This example represents a 480V AC input system with five motors and mixed product family drives. The acceleration and deceleration times are
assumed to be less than 1 minute so we can take advantage of the overload duty of the inverter drives and the bus supply.
Bold text in the tables represents calculated values based on the calculation methods described earlier.
Step 1 is summarized in the following table.
• All drive products are rated for 480V AC system power voltage.
• The PowerFlex 750-Series rated DC amps data is taken from Table 9 on page 66
in Appendix A.
• The PowerFlex 755TM common bus inverter rated DC amps data is taken from Table 10 on page 68
in Appendix A.
• The Kinetix 5700 servo drive DC amps data is taken from Table 11 on page 69
in Appendix A.
The rated DC output current for the bus supply must be at least 2595.9 A DC heavy duty (HD).
2. Use Table 13 on page 72
to select the PowerFlex 755TM non-regenerative bus supply.
Because the DC bus current exceeds the rating of a single density non-regenerative module, it’s necessary to parallel non-regenerative
supply single density (1X) and dual density (2X) power modules. See Paralleling PowerFlex 755TM Non-regenerative Modules on page 41
for
more information about paralleling modules.
For this example, two dual density (2X) modules and one single density (1X) module are paralleled.
The parallel PowerFlex 755TM non-regenerative supply total heavy duty (HD) continuous DC output current is 3290 A DC.
3. Verify that the system AC and DC bus bars and cables are sized to support the expected current. See PowerFlex 755TM System DC Bus
Ratings on page 99 for ratings of PowerFlex 755TM power bus systems. For this example, the total rated DC amps (2595.9 A DC) is less than
the PowerFlex 755TM standard 3000A DC bus bar.
4. Verify that the DC bus capacitance to output amps ratio meets or exceeds the target µF/A ratio. See DC Bus Capacitance Calculation Method
on page 87.
• The PowerFlex 750-Series internal DC bus capacitance data is taken from in 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 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
.
This example is 480V AC and has a mixture of PowerFlex 750-Series drives, PowerFlex 755TM common bus inverters, and Kinetix 5700 servo drives.
The target DC bus capacitance to output current ratio is 40 µF/A.
To meet the target µF/A ratio, it’s necessary to include one 30000 µF 2X capacitor bank and one 15000 µF 1X capacitor bank in the PowerFlex 755TM
non-regenerative supply modules.
Sum the internal DC bus capacitance of the inverter/drives and non-regenerative supply. In this example, 71420 µF+30000 µF = 101420 µF.
Sum the rated AC output current of the inverter/drives. Alternatively, sum the rated DC input amps of the inverter/drives and multiply this value by
0.9 to obtain the approximate AC RMS output current. In this example, 3000 AA DC * 0.9 = 2336.3 A RMS.
The resulting DC bus capacitance to output amps ratio is 101420 µF / 2336.3 A RMS = 43.4 µF/A, which exceeds the target of 40 µF/A.
Section Name Drive Product Cat. No. Rated DC Amps Notes
Drive 1 PowerFlex F755TM 20G…D1K6 1568 frame 10, HD
Drive 2 PowerFlex 755 20G…D096 84.5 frame 5, HD
Drive 3 PowerFlex 755TM 20G…D960 883 frame 9, HD
Drive 4 PowerFlex 755 20G…D022 14.7 frame 2, HD
Drive 5 Kinetix 5700 2198-S086 45.7 ND
Total Rated DC Amps 2595.9 HD
IMPORTANT The PowerFlex 755TM non-regenerative bus supply does not contain
overload protective devices. Make sure that you provide AC overload
protective devices that protects the non-regenerative supply,
associated AC and DC conductors, and bus bars.
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