VFD68 Variable Frequency Drives (575 VAC)
14
Calculating the Maximum Wire Length
1.
Use the recommended wire size in accordance with local, national, and regional regulations to determine
the electrical resistance of the wire (R) according to Table 10.
2.
Find the rated voltage (V) and maximum output current (I) from the rating plate on the selected VFD68
Drive.
3.
Use Figure 7 to determine the maximum recommended wiring length for the VFD68 Drive.
Note:
If the maximum wire length needs to be extended, select a larger wire size and recalculate the
maximum wire length.
Do not exceed 100 m.
Note:
Maximum wiring length is also affected by the setting of P. 72. See
Example:
Given a VFD68DGM-2C model, what is the maximum wiring length?
a.
Table 1 on page 4 indicates that a VFD68DGM-2C model is a 575 VAC Drive, rated for 1.49 kW (2
HP).
b.
The rating information plate (Figure 1 on page 4) for that model indicates that the VFD68DGM Drive
has a voltage rating of 575 VAC and a maximum output rating of 7 amperes.
c.
Table 9 on page 13 gives the recommended wire size as 14 AWG.
d.
Table 10 on page 14 shows 14 AWG size wire as having an electrical resistance of 8.28 milliohms/
meter.
e.
Using the equation in Figure 7 on page 14 and using the values we found in the steps above:
(11.5 * 230) / (7 * 8.28) = 2656.6 / 57.96 = 45.8
The maximum wire length is 45.8 meters.
Table 10: Electrical Resistance by Wire Size
Recommended
Wire Size
1
1.
The mm wire sizes that are given as equivalences to the AWG wire sizes are not commercially available.
Electrical Resistance of
Wire (milliohms/meter)
Recommended
Wire Size
Electrical Resistance of
Wire (milliohms/meter)
25
mm
2
0.727
5.3
mm
2
(
10 AWG)
3.28
21.2
mm
2
(
4 AWG)
0.815
4
mm
2
4.61
16 mm
1.15
3.3
mm
2
(
12 AWG)
5.21
13.3
mm
2
(
6 AWG)
1.30
2.5
mm
2
7.41
10
mm
2
1.83
2
mm
2
(
14 AWG)
8.28
8.3
mm
2
(
8 AWG)
2.06
1.5
mm
2
12.1
6
mm
2
3.08
Figure 7: Maximum Wire Length Calculation
Maximum Wire Length =
(11.55 *V)
(I*R)
V = Voltage rating (575 VAC)
I = Maximum output current (amperes)
R = Electrical resistance of the wire (milliohms/meter)
F
IG
:m
x
w
rl
n
gt
h_5
75
