Hitachi SJ700D-004L, Instruction Manual

Page: 253 / 288

Chapter6 Maintenance and Inspection
6-4
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
Measurement result

(red)

(black)
C
o
n
ve
rt
e
r c
ir
cui
t
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
In
ve
rt
e
r c
ir
cui
t
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
B
R
D
c
ir
cui
t
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