3-27
3.12 Input Power and Motor Cable Length
The length of the cables between the input power source and /or the motor and inverter can cause a
significant phase to phase voltage reduction due to the voltage drop across the cables. The wire size
shown in Tables 3.13.1 is based on a maximum voltage drop of 2%. If this value is exceeded, a wire size
having larger diameter may be needed. To calculate phase tot phase voltage drop, apply the following
formula:
Phase-to-phase voltage drop (V) =
3
×resistance of wire (Ω/km) × length of line m) × current×10
-3
.
(km=3280 x feet)
(m=3.28 x feet )
3.13 Cable Length vs. Carrier Frequency
The allowable setting of the PWM carrier frequency is also determined by motor cable length and is
specified in the following Table 3.13.1.
Table 3.13.1 Cable Length vs. Carrier Frequency
Cable length between
the inverter and
Motor in m (ft.).
< 3 0 m
( 1 0 0 )
3 0
– 50
( 1 0 0
– 165)
5 0
– 100
( 1 6 6 - 3 2 8 )
> 1 0 0
( 3 2 9 )
Recommended carrier
frequency allowed
Parameter 11-01
1 6 k H z
( m a x )
1 0 k H z
( m a x )
5 k H z
( m a x )
2 k H z
( m a x )
3.14 Installing an AC Line Reactor
If the inverter is connected to a large-capacity power source (600kVA or more), install an optional AC
reactor on the input side of the inverter. This also improves the power factor on the power supply side.
