Auto Operation - Hitachi NEXT Series Instruction Manual

8. STANDARD COMPONENTS AND SUBSYSTEMS [Capacity Control System]

8.4.2 AUTO Operation

AUTO operation is Auto start - stop function in addition
to a standard on-off line, 0% or 100% capacity 2-step
control. The CPU on the PC board is continually
calculating a load ratio.
STARTING
Suction throttle valve (STV) closed
START button ON
Airend starts rotation to
compress minor amounts of air
Starts in no load
Changes to full voltage
delta connection
3-way solenoid valve (20Ux)
switched over to connect
Chamber (A) & Chamber (C)
Suction throttle valve (STV) opens
Loading
What is the plant
compressed air piping
Less
pressure ?
10 seconds
than
or more
specified
More than specified
68
(Only for Fixed Speed Type)
UNLOADING RELOADING
Air demand increases
Air demand decreases
Discharge pipe pressure rises Discharge pipe pressure drops
Pressure sensor (PS) operates Pressure sensor (PS) operates
3-way solenoid valve (20Ux) 3-way solenoid valve (20Ux)
switched over to pressurize switched over to pressurize
Chamber (A) Chamber (B)
Suction throttle valve
Suction throttle valve
(STV) opens
(STV) closes
Blowoffvalve opens Blowoff valve closes
Loading
Internal air in discharge
pipe is exhausted to
atmosphere
How long has
Less than 15 minutes
motor been
running ?
15 minutes or more
30% or more
Load ratio ?
Less than 30%
Has motor stopped and
YES
restarted 3 times or more for
150 minutes ?
NO
Motor stops automatically
How long has
motor been
stopped ?
Less than
10 seconds
When the load ratio is less than 30%. CPU stop the main
motor. And automatically restar t when the line
pressure is dropped to cut-in pressure.
STOPPING
STOP button ON
3-way solenoid valve (20Ux)
switched over to pressurize
Chamber (A)
Suction throttle valve
(STV) closes
Blowoff valve opens
Internal air in discharge
pipe is exhausted to
atmosphere
Compressor stops
I f 1 2 0 m i n u t e s o r m o re h a s
passed after the third stop, the
motor will continue to operate
for a minimum of 30 minutes
after restart of the air compres-
sor, and then return to the initial
150 minute cycle.
Load-Unload Operation
AUTO Operation
STV: Suction Throttle Valve
20Ux: 3-Way Solenoid Valve