15
4-5 Wiring
1) Extremely low or high voltage power supply may cause the failure of the compressor. Low power
capacity also causes significant voltage drop when starting up the compressor. The compressor
requires at least 85% of the rated voltage for a start-up, which shall be maintained within ±10% of
the rated voltage during the operation. The inter-phase voltage imbalance shall be within 2%, not
exceeding 3% even in a special case.
2) Features and Capacity
See Table 4-4 Electrical Specification for an appropriate electric power, an operating current and a
starting current. Considering that the discharge air pressure abnormally exceeding the rated
operating pressure increases the operating current, wiring shall allow about 120% of the rated
capacity of a main transformer.
3) See Table 4-4 Electrical Specification for the electric power [kW] and the power factor [%].
4) Minimum Capacity of Transformer [kVA] = {Electric Power [kW] / Power Factor [%]} x 100 x 1.2
5)
Longer lead-in wiring of the main power may cause the compressor failed or tripped during the
start-up due to the voltage drop in the line. Select the thickness of the cable so that it maintains at
least minimum starting voltage.
6) The calculation of the voltage drop based on the line length is as follows:
3-Phase 3-Line Type Connection:
Where,
I = Current [A] A = Cross Section of Cable [mm2] e = Voltage Drop [V] L = Length of Cable [M]
INSTALLATION
4-4 Requirements for the Piping
1) Use a larger diameter and install the pipe without an excessive bending to reduce the pressure
drop.
2) Always place a branch pipe on the top of a main pipe to reduce the discharge of oil or water.
3) For the compressed air pipes, reduce the number of sections bending and connecting, and the
number of valves installed to reduce the pressure loss.
4)
The increased pressure loss requires a high discharge pressure of the air compressor.
Consequently, it causes the power loss. The water stays wherever the pipe is sagging to increase
the pipe resistance, which may cause winter-sowing. Thus, consider the pipe straightness when
installing the pipes.
5) Install a bypass piping on each equipment for a maintenance.
6) A scroll air compressor has a check valve in the system. Installing more check valves between the
compressor and the air receiver tank may cause a malfunction of the compressor.
7) Always install a drain valve on the bottom of a vertical pipe for the prevention of a winter-sowing.
e =
30.8 x L x I
1000 x A
