Rockwell Automation 1336-SN-SP20A Snubber Board Kit - Manual (Page 23)

1336-5.40 – August, 1999
I-23
SCR and Diode Assembly Test 1. The IGBT and Precharge assembly is shown in Figure I-12. The
assembly is shown removed from the main frame for clarity. It is
not necessary to remove the IGBT and Precharge assembly from
the main frame to do this test, or to install the RC Snubber Kit.
2. The Diode and the SCR heat sinks must be electrically isolated
from each other and from the rest of the power circuit, to properly
test the individual components.
3. To isolate the Diode from the rest of the power circuit, remove the
U-shaped bus bar that connects the Diode heat sink to the SCR
heat sink, refer to Figure I-12.
4. To isolate the SCR from the Capacitor Bank, remove the
precharge to spine flex bus, refer to Figure I-12. Disconnect the
SCR gate lead and cathode lead connector. This connector is
located in the wire harness between the precharge board and the
SCR.
5. Remove the four screws that hold the heat sink guard in place.
Pull the guard out about 25 mm (1 in.), or just far enough to gain
access to the lower edge of the SCR heat sink.
6. When testing the Diode or SCR it is important that the Diode and
SCR clamps be at their normal torques.
7. Resistance or voltage checks made on the Diode or SCR heat
sinks must be made to the heat sink aluminum base plate, not the
aluminum fins, refer to Figure I-12. The heat sinks have an epoxy
bonded fin, and many of the fins are NOT electrically connected
to the aluminum base plate.
8. Diode checks:
1 2
Diode (Upper Heat Sink)
Left Right
3
SCR (Lower Heat Sink)
G C
4
Left Right
Meter Leads
Ohms Reading Diode Scale Volts
1 2
+ - 1 to 3 M
Ω
Open
- + 0 to 0.4M
Ω
0.3 to 0.4 V