!
13
Caution
Observe the following guidelines when wiring.
•
Lead size should be determined considering voltage drop of
leads. Select the lead size so that the voltage drop will be within
2% of the normal rated voltage. The voltage drop can be obtained
from the lead resistance (R) in
Ω
/km, wiring distance (D) in
meters, and current (I) in A using the following equation:
Phase-to-phase voltage drop in volts =
√
3
×
R
×
D
×
I
×
10
–3
•
Insertion of AC reactor:
When the power supply capacity exceeds 600 kVA, connect an
AC reactor at the Inverter input side for power supply coordina-
tion. This reactor is also effective in improving the power factor
of the power supply.
•
Wiring length between Inverter and motor:
If the total wiring distance between the Inverter and motor is
excessively long and the Inverter carrier frequency (main tran-
sistor switching frequency) is high, harmonic leakage current
from the cable will increase to affect the Inverter Unit or periph-
eral devices. If the wiring distance between the Inverter and
motor is long, reduce the Inverter carrier frequency as shown
below. The carrier frequency can be set with constant No. 40.
For details, refer to
2-8-18 Carrier Frequency. The carrier fre-
quency is set to 10 kHz at the factory prior to shipping.
Wiring distance between Inverter and motor
Up to 30 m
Up to 50 m
Up to 100 m
Over 100 m
Allowable carrier frequency
(Corresponding setting for constant no. 40)
15 kHz max.
(6)
10 kHz max.
(4)
5 kHz max.
(2)
2.5 kHz max.
(1)
Grounding
Ground the casing of the 3G3XV using ground terminal G (E).
•
Ground resistance should be 100
Ω
or less.
•
Never ground the 3G3XV in common with welding machines,
motors, and other large-current electrical equipment, or ground
pole. Run the ground lead in a separate conduit from leads for
large-current electrical equipment.
•
Use the ground leads which comply with AWG standards and
make the length as short as possible.
•
Where several 3G3XV Units are used side by side, all the Units
should preferably be grounded directly to the ground poles. How-
ever, connecting all the ground terminals of 3G3XV in parallel,
and grounding only one of 3G3XV to the ground pole is also per-
missible as shown below. However, do not form a loop with the
ground leads.
Good
(a)
Poor
(b)
Wiring
Section 1-4
