9. MAINTENANCE [How to Service the Air Compressor]
91
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
② Cleaning
Clean the main 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.
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
office.
Motor Diagnostics and Troubleshooting
Phenomenon
Cause
Abnormal noise
Abnormal rotation
Vibration
Overheat
Thermal relay operation
Circuit breaker operation
Electric Leak
Low Insulation Resistance
Corrective Action
Frame
Bearing
Installation
Loose bolts
○◎○
Retighten the bolts.
Wiring
Poor gounding
◎
Ground properly.
Inadequate breaker capacity
Note 3
○
◎
Replace with properly specified capacity breaker.
Broken wires
○
Install new wires.
Failed breaker, controller or contactor
○
Note 3
○
Check the contacts and replace if necessary.
Environment
Reduced cooling performance due
to dust accumulation
○
Properly clean motor.
Excessive ambient operating
temperature
◎○◎
Improve the room ventilation or contact the local
Hitachi distributor.
High humidity
◎
Contact the local Hitachi distributor
Large external vibration/shock
◎
Take countermeasures against vibration and shock.
Power
Single-phase operationv
◎◎○◎ ◎○
Check the connections of circuit breaker, switch
andvlead wire.
Widely dropped voltage
○○ ◎ ◎
Check the wire thickness and length and contact the
local power utilities company.
Fluctuating voltage
○○○○
Contact the local power utilities company.
Load
Overload
○◎◎○
Check the capacity controller of compressor.
Thrust force by the machine
○○◎
Center the shaft.
Excessive bearing noise NOTE 2
◎◎◎○
Contact the local Hitachi distributor.
Burnt motor coil NOTE 2
○○ ○ ◎◎◎○
Contact the local Hitachi distributor.
NOTES)
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.
13
Maintenance of Main Motor
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