Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control - Manual (Page 50)

50 Rockwell Automation Publication 7000-UM202B-EN-P - June 2014
Chapter 3 Component Definition and Maintenance
5. Connect a low voltage single-phase test power, for instance 110V or 220V,
across a phase and the neutral of the capacitor. Switch on the test power
and measure the test voltage and current drawn by the capacitor. Repeat
the test for all three phases and note down the test voltage and current.
6. Calculate the capacitance from the measured values of test voltage and
current. For a good capacitor, the calculated capacitance value for each of
the three readings should be within ±15% of the capacitor nameplate
micro-Farad. If it is outside this range, the capacitor must be replaced.
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.
Converter Cabinet
Components This section describes the converter cabinet components of your PowerFlex 7000
“B” Frame drive. It also details a number of regular or recurring maintenance
tasks that will keep your drive in peak operating condition.
The converter cabinet contains three rectifier modules and three inverter
modules. Isolated Gate Driver Power Supplies (IGDPS) are available on the
cabinet’s right side sheet.
Thermal sensors are available on the top module of the inverter and rectifier. The
exact location depends on the drive configuration. These sensors connect to
temperature feedback boards that return signals to the drive control.
For control/cabling cabinets, see Control / Cabling Cabinet Components on
page 25 . For DC link/fan cabinets, see DC Link and Fan Cabinet Components
on page 111 .
ATTENTION: The capacitor will charge during this test so take care to prevent a
shock or injury. When moving the test connections from one phase to the next,
wait five minutes minimum for the capacitor to discharge.
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.