Cable Size And Wiring Distance - Mitsubishi Electric FR-A700 Technical Manual

3.6.4

Cable size and wiring distance

(1) Main circuit cables
Like that of a general power cable, determine the size
of the main circuit cables after examining its current
capacity, short circuit protection and cable voltage
drop.
The effective value of the inverter primary current
must be noted because a current larger than the
motor current may flow depending on the inverter
input power factor (see page 505). If the wiring
distance of the cable between the inverter and motor
Applicable Inverter
Standard
Motor
4P (kW)
Type
0.4 FR-A720-0.4K
0.75 FR-A720-0.75K
1.5 FR-A720-1.5K
2.2 FR-A720-2.2K
3.7 FR-A720-3.7K
5.5 FR-A720-5.5K
7.5 FR-A720-7.5K
11 FR-A720-11K
15 FR-A720-15K
18.5 FR-A720-18.5K
22 FR-A720-22K
30 FR-A720-30K
37 FR-A720-37K
45 FR-A720-45K
55 FR-A720-55K
75 FR-A720-75K
90 FR-A720-90K
The line voltage drop can be calculated by the following
expression:
Line voltage drop [V]
cable resistance
[mΩ/m]
=
Use a larger diameter cable when the wiring distance is
long or when it is desired to decrease the voltage drop
(torque reduction) in the low speed range.
* When it is desired to use a larger-diameter cable but it
cannot be connected directly with the motor and
inverter terminals, provide relay terminal boxes as
shown below:
Relay terminal boxes
Power
Inverter
Standard
cable
Wiring length to the motor
When the wiring distance between the inverter and
motor is long, overcurrent protection may be activated
by the influence of the charging current (leakage current)
due to the stray capacity of the wiring in addition to the
aforementioned voltage drop. (The overall wiring length
for connection of multiple motors should be within the
value in the table below.)
Voltage drop over wiring distance of 30m
Inverter Output
Voltage
Current(A) 60Hz(V) 6Hz(V)
3 220 34
5 220 34
8 220 30
11 220 30
17.5 220 30
24 220 28
33 220 28
46 220 26
61 220 26
76 220 26
90 220 26
115 220 26
145 220 26
175 220 26
215 220 26
288 220 24
346 220 24
wiring
current[A]
distance[m]
1,000
Motor
Standard
Large diameter
cable
cable
is long, the voltage drop increases, causing a
reduction in motor torque and the current to increase.
In an extreme case, the motor may overheat. Note
that especially when the output frequency is low, the
output voltage of the inverter is also low and the rate
of voltage drop increases.
Select the cable size so that the voltage drop
between the inverter and motor is 2% of the rated
voltage.
Standard Applicable Cable
Cable diameter Conductor resistance
2
(mm ) 20
2 9.24
2 9.24
2 9.24
2 9.24
3.5 5.20
5.5 3.33
8 2.31
14 1.30
22 0.824
38 0.487
38 0.487
60 0.303
80 0.229
100 0.180
100 0.18
125 0.156
150 0.136
A700 F700
The [Pr. 72 PWM
frequency selection]
setting
2(2kHz) or less
3 to 15 (3kHz to 14.5kHz)
The [Pr. 72 PWM
frequency
selection] setting
200V
class
1(1kHz) or
less
400V
class
200V
2 to 15
class
(2kHz to
400V
14.5kHz)
class
The wiring length should be 100m maximum for vector control.
When Advanced magnetic flux vector control has been
selected, the cable length should be within 30m. A longer
cable may cause speed fluctuation at low speed, in
addition to reduced torque. Perform offline auto tuning in
the state where wiring work is performed when the wiring
length exceeds 30m.
When driving a 400V class motor by an inverter, serge
voltage may occur at the motor terminals because of the
530
SELECTION
(220V supplied) ...... reference value
Line Voltage Drop over
30m
Voltage
60Hz(%) 6Hz(%)
drop (V)
(m /m)
1.44 0.65
2.40 1.09
3.84 1.75
5.27 2.39
4.72 2.14
4.14 1.88
3.96 1.80
3.11 1.41
2.61 1.19
1.92 0.87
2.28 1.04
1.81 0.82
1.72 0.78
1.64 0.75
2.00 0.90
2.33 1.05
2.44 1.10
0.4K 0.75K 1.5K or more
A700
0.75K 1.5K
F700
300m 500m
200m 300m
0.1K 0.2K 0.4K 0.75K 1.5K 2.2K
500
200m 200m 300m 500m
300
- - 200m 200m
500
30m 100m 200m 300m
200
- - 30m 100m
4.2
7.1
12.8
17.5
15.7
14.7
14.1
12.0
10.0
7.4
8.8
7.0
6.6
6.3
7.6
9.7
10.1
2.2K or more
500m
500m
3.7K
or
more
500m 500m
m
500m 500m
m
500m 500m
m
300m 500m
m