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L100 Inverter
Troubleshooting
and Maintenance
6–15
IGBT Test Method
The following procedure will check the inverter transistors (IGBTs) and diodes:
1. Disconnect input power to terminals [R, S, and T] and motor terminals [U, V, and W].
2. Disconnect any wires from terminals [+] and [–] for regenerative braking.
3. Use a Digital Volt Meter (DVM) and set it for 1Ω resistance range. You can check the
status of the charging state of terminals [R, S, T, U, V, W, +, and –] of the inverter and
the probe of the DVM by measuring the charging state.
Table Legend – Almost infinite resistance: ≅ ∞ Ω Almost zero resistance: ≅ 0 Ω
NOTE: The resistance values for the diodes or the transistors will not be exactly the
same, but they will be close. If you find a significance difference, a problem may exist.
NOTE: Before measuring the voltage between [+] and [–] with the DC current range,
confirm that the smoothing capacitor is discharged fully, then execute the tests.
Part
DVM
Measured
Value
Part
DVM
Measured
Value
Part
DVM
Measured
Value
+ – + – + –
D1 [R] +1 ≅ ∞ Ω D5 [S] [N] ≅ 0 Ω TR4 [U] [–] ≅ 0 Ω
+1 [R] ≅ 0 Ω [N] [S] ≅ ∞ Ω [–] [U] ≅ ∞ Ω
D2 [S] +1 ≅ ∞ Ω D6 [T] [N] ≅ 0 Ω TR5 [V] [–] ≅ 0 Ω
+1 [S] ≅ 0 Ω [N] [T] ≅ ∞ Ω [–] [V] ≅ ∞ Ω
D3 [T] +1 ≅ ∞ Ω TR1 [U] [+] ≅ ∞ Ω TR6 [W] [–] ≅ 0 Ω
+1 [T] ≅ 0 Ω [+] [U] ≅ 0 Ω [–] [W] ≅ ∞ Ω
D4 [R] [N] ≅ 0 Ω TR2 [V] [+] ≅ ∞ Ω TR7 [RB] [+] ≅ 0 Ω
[N] [R] ≅ ∞ Ω [+] [V] ≅ 0 Ω [+] [RB] ≅ ∞ Ω
TR3 [W] [+] ≅ ∞ Ω [RB] [–] ≅ 0 Ω
[+] [W] ≅ 0 Ω [–] [RB] ≅ 0 Ω
[R]
[S]
[T]
TR1 TR2 TR3
[U]
[V]
[W]
[–]
D1 D2 D3
D4 D5 D6
+
[+][+1]
TR4 TR5 TR6