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6.5 Method of Checking the Inverter and Converter Circuits
You can check the quality of the inverter and converter circuits by using a tester.
(Preparation)
1) Remove the external power supply cables from terminals R, T, and T, the motor cables from terminals U, V, and W,
and the regenerative braking resistor cables from terminals P and RB.
2) Prepare a tester. (Use the 1Ω-measuring range.)
(Checking method)
Measure the current conduction at each of the inverter's main circuit terminals R, S, T, U, V, W, RB, P, and N while
switching the tester polarity alternately.
Note 1:
Before checking the circuits, measure the voltage across terminals P and N with the tester in DC voltage
range mode to confirm that the smoothing capacitor has fully discharged electricity.
Note 2:
When the measured terminal is nonconductive, the tester reads a nearly infinite resistance. The tester may
not read the infinite resistance if the measured terminal flows a current momentarily under the influence of
the smoothing capacitor.
When the measured terminal is conductive, the tester reading is several ohms to several tens of ohms. The
measured values may vary slightly, depending on the types of circuit devices and tester. However, if the
values measured at the terminals are almost the same, the inverter and converter circuits have adequate
quality.
Note 3:
Only inverter models with capacity of 22 kW or less have the BRD circuit.
Tester polarity
(red)
(black)
R
PD
D1
PD
R
S
PD
D2
PD
S
T
PD
D3
PD
T
R
N
D4
N
R
S
N
D5
N
S
T
N
D6
N
T
U
P
TR1
P
U
V
P
TR2
P
V
W
P
TR3
P
W
U
N
TR4
N
U
V
N
TR5
N
V
W
N
TR6
N
W
RB
P
P
RB
TR7
RB
N
N
RV
Measurement result
Nonconductive
Conductive
Nonconductive
Conductive
Nonconductive
Conductive
Conductive
Nonconductive
R
Conductive
Nonconductive
S
Conductive
Nonconductive
T
Nonconductive
Conductive
Nonconductive
Conductive
Nonconductive
Conductive
Conductive
Nonconductive
Conductive
Nonconductive
Conductive
Nonconductive
Nonconductive
Conductive
Nonconductive
Nonconductive
Chapter 6 Maintenance and Inspection
BRD circuit
PD
P
RB
Converter circuit
D1
D2
D3
C+
D4
D5
D6
N
6-4
Inverter circuit
TR1
TR2
TR3
TR7
TR4
TR5
TR6
U
V
W
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