Rockwell Automation Publication DRIVES-AT005D-EN-P - May 2022 27
Chapter 2 Regenerative Bus Supply Configuration
Example Advanced Sizing PowerFlex 755TM Regenerative Bus Supply Calculation
This example represents a 600V AC input system with five motors and 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 table represents calculated values that are based on the calculation methods described earlier.
Steps 1…5 are summarized in the following table.
• All drive products are rated for 600V AC system power voltage
• PMaccel, PMrun, and PMdecel are the motor shaft power requirements of the application
• PAccel, PRun, and PDecel are the calculated DC input power requirements of the inverter drives
6. The highest output absolute value power total is 291.6 kW heavy duty (HD). Use this value to select the minimum DC output power for the
PowerFlex 755TM regenerative bus supply.
7. Use Table 16 on page 76
in Appendix A, to select the output power rating 600V AC PowerFlex 755TM regenerative bus supply that supports
the value in step 6. A 20Jx6…E395 frame 7 or 20JxF…E395 frame 8 with an HD DC output power rating of 317 kW and 365 A DC meets the
requirements. For this example, the frame 8 product is chosen.
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 14 on page 73
in Appendix A.
• The PowerFlex 755TM common bus inverter internal DC bus capacitance data is taken from Table 15 on page 75
in Appendix A.
• The PowerFlex 755TM regenerative bus supply internal and maximum external capacitance data is taken from Table 16 on page 76
in
Appendix A. The PowerFlex 755TM regenerative bus supply internal bus capacitance value isn’t included in the total external capacitance
calculation.
Verify that the µF/A ratio meets or exceeds the target of 28 µF/A ratio for this 600V AC system with mixed inverter types. The following table
summarizes the DC bus capacitance data and calculations.
Sum the internal DC bus capacitance of the inverter/drives and regenerative bus supply. In this example, 19900 µF + 4650 µF = 24550 µF
Sum the AC output currents of the inverter/drives. In this example, 629.0 A RMS.
The calculated system µF/A ratio of 24550 µF / 629 A RMS = 39.0 µF/A exceeds the design target of 28 µF/A. No additional bus capacitance
is required for this common DC bus system.
Section
Name
Motor Nameplate Accel DC Bus Power
Run DC Bus Power
(kW)
Decel DC Bus Power (kW)
Power (kW) Efficiency PMaccel PAccel PMrun
PRun
(1)
(1) Drive output power calculations include factors for polarity of power, motor efficiency, and inverter efficiency.
PMdecel
PDecel
(2)
(2) Output power total calculations include overload duty of the bus supply
Drive 1 112 0.95 20.0 21.70 -90.0 -82.94 -120.0 -110.58
Drive 2 75 0.8 97.0 125.0 68.0 87.63 -80.0 -62.08
Drive 3 150 0.96 210.0 225.52 130.0 139.60 -210.0 -195.55
Drive 4 30 0.87 35.0 41.47 24.0 28.44 -35.0 -29.54
Drive 5 18 0.87 20.0 23.70 15.0 17.77 -20.0 -16.88
Bus Supply
OL Duty
None = 1
ND = 1.1
HD = 1.5
1.5
DC Bus Input Power
Totals
291.6 190.5 -276.4
Bus Supply Min DC Output
Power Rating
291.6 kW HD
To Next Page
Loading...
Need help?
General
