7.6.1
Power Source Transformer and
Power Cable
Prepare a power source transformer with adequate
capacity. Also, use a power cable with adequate length
and size. Otherwise, a voltage drop will occur when
attempting to start the
SCREW, and as a result the
motor will fail to start. A voltage drop will also occur
during operation, which deenergizes the control circuit
and shut the air compressor down. To control a drop of
starting voltage within an allowable range (5% of the
rated voltage), use the adequate power source trans-
former and power cable as follows:
The inter phase voltage unbalance factor of power sup-
ply shall net exceed 1%.
1． Personnel who carry out the wiring work must have a license. Ask personnel who have license. Wiring
work by personnel without license may cause troubles like electric shock accident.
2． Do not take the protective relay off the compressor or make any modification which might hinder its
relay function on the electrical circuit. Such modification will remove its protective functions and may
cause to serious accident like burning the compressor. Ask your dealer if you must have a
modification to the unit.
3． When opening starter/control box cover for wiring or inspection, disconnect the main power to pre-
vent accidental electrical shock and allows about 10 minutes to roll on after the power-off before com-
mencing the work. For the inspecting of the recharge section, wait until the charge lamps of the DCBL
controller and fan inverter completely go off and hang a warning flag that warning not to turn the
power on because inspection is being carried out to prevent so that nobody turns the power back on
while inspection is being performed.
7.6.2
Connecting earth leakage circuit
breaker
Be sure to use a earth leakage circuit breaker for the
circuit breaker. For motor protection, select the earth
leakage circuit breaker based on the below table and
equip to the main POWER line of the compressor.
If earth leakage circuit breaker other than Hitachi
brand is used, contact your Hitachi Authorized dealer
for the detaile.
Type
Frequency
(Hz)
Power
Voltage
(V)
Rated
Current
(A)
Starting
Current
(A)
IPI Tripping
Current
(A)
Rated Cut-Off
Capacity
(kA)
55kW 50
380 116 116 440 50
400 110 110 440 50
415 106 106 440 50
75kW 50
380 158 158 596 50
400 150 150 596 50
415 145 145 596 50
Use an earth leakage circuit breaker with current sensitivity of 200 mA.
These are values for the cables less than 10m in length.
For over 10m, thicker cable is required. In such case,
keep the thickness below its maximum value on the com-
pressor side by using intermediate terminals.
IMPORTANT
Type 55kW 75kW
Power
Transformer
Capacity (kVA)
400V
Class
Over 100 Over 150
Power Cable
Thickness
(mm
2
)
400V
Class
Over 38, Max.100 Over 60, Max.150
・The DCBL controller of
SCREW contains a DC
reactor to suppress harmonic current. Therefore,
use the power supply that provides a specified volt-
age (the rated voltage ± 5%).
・When you want to use a private power generator,
select the one that is 5 to 6 times larger in capacity
than the motor output so as to avoid an accident
caused by harmonic current from the DCBL controller.
7.6 Instructions on Electrical Wiring
WARNING
● Be sure to equip a earth leakage circuit
breaker to the Power. Wiring with only dis-
connector like knife switch is not sufficient
and may not protect the compressor and
cause burning when short circuit occurs.
● Be sure that the compressor is appropriate-
ly grounded. If not, this can cause electric
shock accident or shutdown to the com-
pressor. Do not use steel skeleton as a
ground for the compressor. This may cause
malfunction. Ground the cable by itself into
the earth.
CAUTION
37
7. INSTRUCTIONS FOR INSTALLATION [Instructions on Electrical Wiring]
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