Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive (A Frame) - ForGe Control - Manual (Page 102)

102 Rockwell Automation Publication 7000A-UM200C-EN-P - June 2014
Chapter 3 Component Definition and Maintenance
This example demonstrates the calculation for capacitance value.
Suppose a capacitor under test is rated at 400 kVAR, 6600V, 50 Hz, 29.2 μF.
Assume you are using 200V, 50 Hz test power with the recorded voltage and
current values for each test as shown in the table below.
Calculate the capacitance using the first reading. In this case:
Similarly, you can calculate the capacitance for the remaining two measurements
for L2-N and L3-N.
DC Link Reactor Replacement The DC Link maintains a low ripple current between the rectifier and the
inverter.
The DC link reactor does not normally require service. In the event of its
replacement, it must be ensured that Rockwell Automation approves the
replacement link.The link has been constructed to ensure that it is cooled by air
drawn through its coils.
To service the DC link, see Figure 85 .
1. Ensure that source power to the drive is locked out and that the filter caps
are fully discharged.
2. Open the door to the DC link cabinet and remove the screws that retain
the vertical sheet metal barrier and low voltage panel.
Phase - Neutral L1-N L2-N L3-N
Test Voltage 200V 200V 200V
Measured Current 1.87 A 1.866 A 1.861 A
V = 200V, I = 1.87 for L1-N
Xc = V/I = 200/1.87 = 106.95
C= 1/ (2
π F Xc)
C= 1/(2 x 3.14 x 50 x 106.95
C=29.7μ
F
Where:
F = frequency of the applied voltage.
ATTENTION: To prevent electrical shock, ensure the main power has been
disconnected before working on the current transformer. Verify that all circuits
are voltage free using a hot stick or appropriate voltage-measuring device.
Failure to do so may result in injury or death.
WARNING: The DC Link may be hot.