Mitsubishi Electric FR-A700 Series, Техническое руководство

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531
SELECTION
S
E
LECTION
3
wiring constant. Isolation of the motor may be deteriorated
by the surge voltage. In that case, refer to page 504. (2) Control circuit cable
The cable size of 0.75mm
2
or larger is enough for
use with cable other than the main circuit cables, e.g.
operation and signal circuits.
3.6.5 Earth leakage circuit breaker (NV)
Since harmonic components are included in the output
voltage of an inverter which drives a motor, an earth
leakage current flows due to the earth capacity of the
electrical path from the inverter to the motor and the stray
capacity between the motor winding and iron core. For this
reason, the rated sensitivity current of the earth leakage
circuit breaker installed in the power supply side of the
inverter should be selected as described below:
z Breaker designed for harmonic and surge suppression
z Standard breaker
Rated sensitivity current
I
n
10 (Ig
1
+Ign+Igi+Ig
2
+Igm)
Rated sensitivity current
I
n
10 {Ig
1
+Ign+Igi
+3 (Ig
2
+Igm)}
Ig
1
, Ig
2
:
Leakage currents in cable path during
commercial power supply operation
Ign
*
: Leakage current of noise filter on inverter
input side
Igm :
Leakage currents of motor during
commercial power supply operation
Igi : Inverter unit leakage current
*1 The earth leakage circuit breaker should be installed
to the primary (power supply) side of the inverter.
*2 An earth (ground) fault on the secondary side of the
inverter can be detected at the running frequency of
120Hz or less.
(200V 60Hz)
(200V 60Hz)
1. 5 3. 7
2. 2
7. 5 1522
11
37
30
55
45 5.5 18. 5
0. 1
0. 2
0. 3
0. 5
0. 7
1. 0
2. 0
0
2 0
4 0
6 0
8 0
100
120
2 3.5
5.5
8 1422
30
38
60
80
100
150
Motor capacity (kW)
Example of leakage current of
cable path per 1km during the
commercial power supply operation
when the CV cable is routed in
metal conduit
Leakage current example of
three-phase induction motor
during the commercial
power supply operation
Leakage currents (mA)
Leakage currents (mA)
Cable size (mm 2 )
Motor capacity (kW)
For " " connection, the amount of leakage current is appox.1/3 of the above value.
(Three-phase three-wire delta
connection 400V60Hz)
Example of leakage current per 1km during
the commercial power supply operation
when the CV cable is routed in metal conduit Leakage current example of three-
phase induction motorduring the
commercial power supply operation
(Totally-enclosed fan-cooled
type motor 400V60Hz)
0
2 0
4 0
6 0
8 0
100
120
leakage currents (mA) leakage currents (mA)
2 3.5
5.5
8 1422
30
38
60
80
100
150
Cable size (mm 2 )
0. 1
0. 2
0. 3
0. 5
0. 7
1. 0
2. 0
1. 5 3. 7
2. 2
7. 5 1522
11
37
30
55
45 5.5 18. 5
*3 In the connection earthed-neutral system, the
sensitivity current is blunt against an earth (ground)
fault in the inverter output side.
Earthing (Grounding) must conform to the
requirements of national and local safety regulations
and electrical codes. (NEC section 250, IEC 536 class
1 and other applicable standards)
*4 When the breaker is installed on the secondary side of the
inverter, it may be unnecessarily operated by harmonics
even if the effective value is less than the rating.
In this case, do not install the breaker since the eddy
current and hysteresis loss will increase, leading to
temperature rise.
*5 General products indicate the following models.
BV-C1, BC-V, NVB, NV-L, NV-G2N, NV-G3NA, NV-2F,
earth leakage relay (except NV-ZHA), NV with AA
neutral wire open-phase protection. The other models
are designed for harmonic and surge suppression.
NV-C, NV-S, MN series, NV30-FA, NV50-FA, BV-C2,
earth leakage alarm breaker (NF-Z), NV-ZHA, NV-H
* Note the leakage current value of the noise filter installed
on the inverter input side.
(Refer to a catalog for the leakage current value of the filter
dedicated to the Mitsubishi inverter)
Breaker Designed
for Harmonic and
Surge Suppression
Standard
Breaker
Leakage current Ig
1
33
5m
= 0.17
1000m
Leakage current Ign 0 (without noise filter)
Leakage current Igi
1 (without EMC filter)
Refer to the table below for the
inverter leakage currents
Leakage current Ig
2
33
50m
= 1.65
1000m
Motor leakage current Igm 0.18
Total leakage current Ig
3.00 *1 6.65 *2
Rated sensitivity current:
(
Ig 10)
30 100
*1 Ig
1
+Ign+Igi+Ig
2
+Igm (Unit : mA)
*2 Ig
1
+Ign+Igi+3 (Igm
2
+Igm)
Noise
filter
Inverter
Ig
1
Ign Igi Ig
2
Igm
5.5mm 2 ˜
5m
5.5mm
2
˜ 50m
IM
3F
200V 2.2kW
NV
[Example]