Method Of Checking The Inverter And Converter Circuits - Hitachi SJ700-055-110LF 2 Series Service Manual

5.5 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
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Measurement result
Nonconductive
Conductive
Nonconductive
Conductive
Converter circuit
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
5 - 4
BRD circuit
PD
P
RB
D1 D2 D3
C+
TR7
D4
D5 D6
N
Inverter circuit
TR1 TR2 TR3
U
V
W
TR4 TR5 TR6