54 Rockwell Automation Publication 7000-UM202D-EN-P - May 2018
Chapter 2 Power 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 that a capacitor under test is rated at 400 kVAR, 6600V, 50 Hz,
29.2 F. Assume that 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. This section 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 right
side sheet of the cabinet.
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 29. For DC link and fan cabinets, see DC Link and Fan Cabinet
Components on page 115.
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=29.7 F
Where:
F = frequency of the applied voltage.
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