Hitachi NEXT Series Instruction Manual page 101

Oil-free rotary screw air compressor
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Maintenance of Main Motor
① Checking the operating temperature
If the LCD monitor indicates main motor overload
[OVERLOAD: MAIN] (fixed-speed type) or
temperature increase of main motor fin [FIN-T]
(Vtype), investigate the cause of the excessive heat
and utilizing the Motor Diagnostics and
Troubleshooting chart below.
② Cleaning
Clean the motor periodically to prevent dust particles
from accumulating inside and outside of the motor.
When servicing the air compressor, measure
the insulation resistance of the motor coil with
a 500V megohmmeter and verify that the
insulation resistance is 1MΩ or more.
Motor Diagnosis and Troubleshooting
Loose bolts
Poor gounding
Inadequate breaker capacity
Broken wires
Failed breaker, controller or contactor
Dust accumulation reduced cooling
Excessive ambient operating
High humidity
Large external vibration/shock
Phase-lacking operation
Widely dropped voltage
Fluctuating voltage
Thrust force by the machine
Excessive bearing noise NOTE 2
Burnt motor coil NOTE 2
1. ◎ : Close relationship between the cause and type of problem. 〇 : Relationship between the cause and type of problem.
2. Detect the fundamental cause of the problem and take corrective action.
3. Breaker, controller or contactors are hot.
9. MAINTENANCE [How to Service the Air Compressor]
Note 3
Note 3
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③ Disassembling
In a severe environment (dirty, corrosive, high dust or
high powder), disassemble and service the motor
every two years. In a normal environment, disassemble
and service the motor every six years. For the most
common motor problems, see the Motor Diagnostic
and Troubleshooting chart below. If the problem
cannot be solved with the chart, contact the local
HITACHI distributor/master dealer or representative
Retighten the bolts.
Ground properly.
Replace with properly specified capacity breaker.
Install new wires.
Check the contacts and replace if necessary.
Properly clean motor.
Improve the room ventilation or contact the local
Hitachi distributor.
◎ Contact the local Hitachi distributor.
Take vibration and shock measurements.
Check the brealer, contactor and motor wirings.
◎ ○
Check the wire thickness and length and contact the
local power utilities company.
Contact the local power utilities company.
Check the capacity control system.
◎ ○
Check the contact condition of bull gear and pinion gear.
Contact the local Hitachi distributor.
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◎ ◎ ◎ ○ Contact the local Hitachi distributor.
Corrective Action

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