Maintenance of Main Motor
① Temperature increase
The motor coil has a specified maximum allowable
temperature rise of 180℉ (100℃), based on an
ambient temperature of 104℉ (40℃). If the motor is
unusually hot during normal operation, regardless of
the specified temperature rise, investigate the cause
of the excessive heat utilizing the Motor Diagnostics
and troubleshooting chart below
Clean the main motor periodically to prevent dust
particles from accumulating inside and outside of
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 Diagnostics and Troubleshooting
Inadequate breaker capacity
Failed breaker, controller or contactor
Reduced cooling performance due
to dust accumulation
Excessive ambient operating
Large external vibration/shock
Widely dropped 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]
◎ ○ ◎
◎ ◎ ○ ◎
In a severe environment (dirty, corrosive, high dust or
high powder), disassemble and ser vice 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 char t, contact the local
HITACHI distributor/master dealer or representative
Retighten the bolts.
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
◎ Contact the local Hitachi distributor
Take countermeasures against vibration and shock.
Check the connections of circuit breaker, switch
Check the wire thickness and length and contact the
local power utilities company.
Contact the local power utilities company.
Check the capacity controller of compressor.
Center the shaft.
Contact the local Hitachi distributor.
◎ ◎ ◎ ○ Contact the local Hitachi distributor.