Mitsubishi Electric FR-A700 Series, Technical Manual

Page: 496 / 550

530
SELECTION
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
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.
The line voltage drop can be calculated by the following
expression:
Line voltage drop [V]
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.
z 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.)
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
Voltage drop over wiring distance of 30m
(220V supplied) ...... reference value
Standard
Motor
4P (kW)
Applicable Inverter
Inverter Output
Voltage
Standard Applicable Cable
Line Voltage Drop over
30m
Type Current(A) 60Hz(V) 6Hz(V)
Cable diameter
(mm
2
)
Conductor resistance
20 (m /m)
Voltage
drop (V)
60Hz(%) 6Hz(%)
0.4 FR-A720-0.4K 3 220 34 2 9.24 1.44 0.65 4.2
0.75 FR-A720-0.75K 5 220 34 2 9.24 2.40 1.09 7.1
1.5 FR-A720-1.5K 8 220 30 2 9.24 3.84 1.75 12.8
2.2 FR-A720-2.2K 11 220 30 2 9.24 5.27 2.39 17.5
3.7 FR-A720-3.7K 17.5 220 30 3.5 5.20 4.72 2.14 15.7
5.5 FR-A720-5.5K 24 220 28 5.5 3.33 4.14 1.88 14.7
7.5 FR-A720-7.5K 33 220 28 8 2.31 3.96 1.80 14.1
11 FR-A720-11K 46 220 26 14 1.30 3.11 1.41 12.0
15 FR-A720-15K 61 220 26 22 0.824 2.61 1.19 10.0
18.5 FR-A720-18.5K 76 220 26 38 0.487 1.92 0.87 7.4
22 FR-A720-22K 90 220 26 38 0.487 2.28 1.04 8.8
30 FR-A720-30K 115 220 26 60 0.303 1.81 0.82 7.0
37 FR-A720-37K 145 220 26 80 0.229 1.72 0.78 6.6
45 FR-A720-45K 175 220 26 100 0.180 1.64 0.75 6.3
55 FR-A720-55K 215 220 26 100 0.18 2.00 0.90 7.6
75 FR-A720-75K 288 220 24 125 0.156 2.33 1.05 9.7
90 FR-A720-90K 346 220 24 150 0.136 2.44 1.10 10.1
=
cable resistance
[m
Ω
/m]
wiring
distance[m]
current[A]
1,000
Motor Inverter
Power
Relay terminal boxes
Standard
cable Large diameter
cable
Standard
cable
* 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:
The [ Pr. 72 PWM
frequency selection ]
setting
0.4K 0.75K 1.5K or more
0.75K 1.5K 2.2K or more
2(2kHz) or less 300m 500m 500m
3 to 15 (3kHz to 14.5kHz) 200m 300m 500m
The [ Pr. 72 PWM
frequency
selection ] setting
0.1K 0.2K 0.4K 0.75K 1.5K 2.2K
3.7K
or
more
1(1kHz) or
less
200V
class
200m 200m 300m 500m
500
m
500m 500m
400V
class
- - 200m 200m
300
m
500m 500m
2 to 15
(2kHz to
14.5kHz)
200V
class
30m 100m 200m 300m
500
m
500m 500m
400V
class
- - 30m 100m
200
m
300m 500m
A700 F700
A700
F700
' &