Chapter 6 Maintenance and Inspection
6 - 4
6.5 Withstand Voltage Test
Do not carry out a withstand voltage test for the inverter. The test may damage its internal parts or cause
them to deteriorate.
6.6 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 30 kW or less have the BRD circuit.
Tester polarity
Measurement result
⊕ (red) \ (black)
Converter circuit
D1
R PD Nonconductive
PD R Conductive
D2
S PD Nonconductive
PD S Conductive
D3
T PD Nonconductive
PD T Conductive
D4
R N Conductive
N R Nonconductive
D5
S N Conductive
N S Nonconductive
D6
T N Conductive
N T Nonconductive
Inverter circuit
TR1
U P Nonconductive
P U Conductive
TR2
V P Nonconductive
P V Conductive
TR3
W P Nonconductive
P W Conductive
TR4
U N Conductive
N U Nonconductive
TR5
V N Conductive
N V Nonconductive
TR6
W N Conductive
N W Nonconductive
BRD circuit
TR7
RB P Nonconductive
P RB Conductive
RB N Nonconductive
N RV Nonconductive
PD
D1
D4
D2
D5
D3
D6
R
S
T
TR4 TR5 TR6
TR1 TR2 TR3
C+
P
N
TR7
RB
U
V
W
Converter circuit
BRD circuit
Inverter circuit
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