5-2
(continued)
Is there unusual odor or damage to the insulation
by overheating?
Olfactory and visual
inspection
Not abnormal
Main circuit
Resistor
Is there an open circuit?
Conduct a visual
inspection or use a
multimeter by removing
the connection on one
side.
Less than about ±
of the indicated
resistance value
Control circuit
Control
PCB and
connector
Are there any loose screws or connectors?
Is there unusual odor or discoloration?
Are there cracks, damage, deformation, or
excessive rust?
Is there electrolyte leakage or deformation to the
capacitor?
Tighten
Olfactory and visual
inspection
Visual inspection
Not abnormal
Is there abnormal sound or vibration?
Aural and visual
inspection. Turn it
manually. (Check the
power supply is off.)
The fan must rotate
smoothly.
Are nuts or bolts loose? Tighten Not abnormal
Cooling fan
Is there discoloration due to overheating? Visual inspection Not abnormal
Cooling circuit
Ventilation
Is there foreign matter on the fins or intake and
exhaust ports?
Visual inspection Not abnormal
Note: If the equipment stained, wipe with a cleaning cloth of chemical neutrality. Vacuum the dust.
5-3 Insulation test
Avoid testing the DB unit with a megger because an insulation test is completed at the factory. If a megger test
must be conducted, proceed as described below. Use of an incorrect test method may result in product damage.
If the specifications for dielectric strength test are not followed, the product may be damaged. If a dielectric
strength test must be performed, contact your local distributor or nearest Fuji Electric's sales office.
(1) Megger test for the main circuit
① Use a 500V DC type megger and isolate the main power supply before commencing measurement.
② If the test voltage is applicable to the control circuit, remove all connection cables to the control circuit.
③ Connect the main circuit terminals using common cables as shown in Fig. 5-3-1.
④ Execute the megger test only between the common cables connected to the main circuit and the ground
(terminal G）.
⑤ A megger indicating 5MΩ or more is normal. (This is the value measured with a DB unit only.)
＋
－
N(-) P(+) P(+)R DB
G
＋－
Megger
Fig. 5-3-1 Megger test
(2) Insulation test for the control circuit
A megger test and a dielectric test must not be performed in the control circuit. Prepare a high resistance
range multimeter for the control circuit.
① Remove all external cables from the control circuit terminals.
② Conduct a continuity test between the control circuits and the ground. A result of 1 MΩ or more is
normal.
(3) Exterior main circuit and sequence control circuit
Remove all cables from the terminals to ensure the test voltage is not applied to the DB unit.
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