Publication 2364F-5.05 - March 1999
4-16
Testing Components
Testing IGBTs
IGBTs can be checked by testing the resistance of the AC terminals with
respect to the DC busbars.
1. Push the disconnect lever to off and wait for all voltage to discharge
from the unit. Do not continue until all voltage has dissipated from the
DC bus.
2. Verify that there is no voltage across the DC bus (see Figure 4.12 and
Figure 4.13 for check points).
3. Test the resistance between L1 and DC Bus+. J, K, and L-code RGUs
should show a high resistance (over 500 k-ohms), M and N-code RGUs
should indicate a resistance of 5 to 10 k-ohms (since two IGBTs are
installed in parallel). Test the other two lines (L2 and L3) with respect to
DC Bus+.
4. Test the resistance of L1, L2, and L3 with respect to DC Bus-. Again,
J, K, and L-code RGUs should read over 500 k-ohms, while M and
N-code RGUs should read 5 to 10 k-ohms.
5. Set meter to check diodes. Take a reading of L1 to DC Bus+ (with
negative lead on the DC bus). A reading of 0.2 to 0.4 volts should be
seen. Test the other two lines with respect to DC Bus+.
6. Take a reading of L1 to DC Bus- (with positive lead on DC bus). Again
a reading of 0.2 to 0.4 volts should be seen. Test the other two lines with
respect to DC Bus-.
Figure 4.11
Testing IGBTs
If any of these tests have failed, the particular IGBTs may be damaged
(opened or shorted). Replace any damaged IGBTs and consider testing the
gate driver board and snubber boards.
Additional test instructions for the IGBTs (power modules) can be seen in
the 1336 FORCE service manuals (see Table 4.A).
Ω
DC Bus +
DC Bus -
L1
L2
L3
