Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) Commissioning - ForGe Control - Manual (Page 46)

46 Rockwell Automation Publication 7000-IN012B-EN-P - June 2014
Chapter 4 Commissioning the Drive
Table 1 - SGCT/snubber resistance values
SGCT Anode-to-Cathode (Sharing) Resistance
The anode-cathode resistance check measures the parallel combination of the
sharing resistor and SGCT anode-cathode resistance. The sharing resistor has a
resistance much lower than that of a good SGCT, so the measurement will be
slightly less than the resistance of the sharing resistor. A measurement between
60 kΩ and 75 kΩ indicates the SGCT is in good condition and that wiring to
the SGCT is correct. If the SGCT fails, it will be in the shorted mode, 0 Ω. The
anode-to-cathode resistance check will be 0 Ω.
There is a test point inside the PowerCage to measure the resistance of the
snubber resistor and capacitance of the snubber capacitor. The test point is the
electrical connection between the snubber resistor and snubber capacitor. Place
one probe of the multi-meter on the test point and the other probe on the
appropriate heat sink to determine the value of the resistor or capacitor. See
Figure 29 .
Figure 29 - SGCT PowerCage
SGCT Resistance Measurement Measured Resistance
Inverter Rectifier (AFE only)
SGCT Anode-Cathode Resistance
(heat sink to heat sink) k- Ω
(Lowest) (Highest) (Lowest) (Highest)
Snubber Resistance
(Test point: Heat sink above)
Ω
(Lowest) (Highest) (Lowest) (Highest)
Snubber Capacitance
(Test Point – heat sink on Right) μF
(Lowest) (Highest) (Lowest) (Highest)
Resistance value between two
heat sinks is sharing resistance in
parallel with anode-cathode
resistance Resistance value between
heat sink and test point is
snubber resistance