Replacing Parts; Replacing Parts; Ground Resistance Test With A Megger - Hitachi L700 SERIES Instruction Manual

6.3

Replacing Parts

The inverter consists of many parts and it functions normally only when all the parts operate normally.
The table below lists the parts that may be subject to changes in characteristics and malfunctions after long-time use,
even normally, over a specified number of years.
Each part should be replaced at specified intervals to prevent inverter faults and changes in inverter characteristics.
Be sure to periodically replace the parts for preventive maintenance.
Part name
Inverter circuit and converter circuit
Cooling fan
DC bus capacitors of main circuit
Electrolytic capacitors on the board
Relay
*1 The operating life of the smoothing capacitor is under the influence of the ambient temperature. Refer to "Smoothing-Capacitor Life Curve," as a standard for the operating life
until replacement.
*2 The operating life of the cooling fan varies depending on environmental conditions, including the ambient temperature and dust. Check the status of the cooling-fan operation
during daily inspections.
*3 The standard operating life (number of years or operation cycles) and the data described in "Smoothing-Capacitor Life Curve," are based on the expected design life, but they
do not indicate the guaranteed life of any parts. Please refer to the manual of each model for Smoothing-Capacitor Life Curve,"
*4 Even if dust is detached when the cooling fan is in the state of the lock by dust, etc. , it takes the time of about 5-10 second to the re-rotation.
*5 Inverter circuit and converter circuit (including resistors) have the thing that the exchange is needed by power cycle life.
*6 It is necessary to exchange it in proportion to accumulation ON-OFF frequency (ON-OFF life).
*7 Please refer to the manual for "Output of Life Warning".

6.4 Ground Resistance Test with a Megger

When testing an external circuit with a megger, disconnect all the external circuit cables from the inverter
to prevent it from being exposed to the test voltage.
Use a tester (in high-resistance range mode) for a conduction test on the control circuit. Do not use a
megger or buzzer for that purpose.
Apply the ground resistance test using a megger only to the main circuit of the inverter. Do not carry out
the test using a megger for its control circuit.
Use a 500 VDC megger for the ground resistance test.
Before the main circuit test with a megger, remove the jumper for switching the inverter's internal filter
function, and then connect terminals R, S, T, U, V, W, P, PD, N, RB, R0, and T0 by wires as shown in the
figure below. Subsequently, carry out the test.
After the test using the megger, remove the wires from terminals R, S, T, U, V, W, P, PD, N, RB, R0, and T0,
and connect the jumper for switching the inverter's internal filter function at the original position.
Note that only inverter models with a capacity of less than 22 kW have the RB terminal.
Power supply
Do not connect
power supply cables
to the inverter.
500 VDC megger
Chapter 6 Maintenance and Inspection
Standard replacement
interval
-
(*5)
10 years
(*2) (*4)(*7)
10 years
(*1) (*3) (*7)
10 years
(*1) (*3)
-
(*6)
P P N
R
S
T
Ground Ground
terminal terminal
R0
T0
Be sure to remove the jumper for
switching the internal filter function.
6 - 3
Replacement and maintenance
methods
Decide whether to replace after
examination.
Replace with a new part.
Replace with a new part.
(Decide whether to replace after
examination.)
Replace with a new part.
(Decide whether to replace after
examination.)
Inspect the part after examination.
Motor
R
U
V
W
Do not connect the
inverter cables to the
motor.
IM