3-13
3.11
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 3.16.1 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 )
3.12 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 3.14.1.
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 )
3.13 Control Circuit Wiring
(1)
Separate the wiring for control circuit terminals from main circuit wiring for terminals
(R/L1, S/L2,
T/L3, U/T1, V/T2, W/T3)
.
(2)
Separate the wiring for control circuit terminals RA-RB (Relay output) from wiring for terminals
S1
– S5
, AVI, ACI and AGND wiring.
(3)
Use shielded twisted-pair cables (#24 - #14 AWG / 0.5 -2
mm
2
) shown in Fig. 3.13.1 for control
circuits to minimize noise problems. The maximum wiring distance should not exceed 50m (165 ft).
Shield
Twisted Pair
Wrap with insulating Tape
Ground Shield at Inverter
end
ONLY
DO NOT Ground Shield at
this end
Fig. 3.13.1 Shielded Twisted-Pair
