Earth Leakage Circuit Breaker (Nv) - Mitsubishi Electric FR-A700 Technical Manual

wiring constant. Isolation of the motor may be deteriorated
by the surge voltage. In that case, refer to page 504.
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:
Breaker designed for harmonic and surge suppression
Rated sensitivity current
I n
Standard breaker
Rated sensitivity current
I n
Leakage currents in cable path during
Ig , Ig :
1 2
commercial power supply operation
Ign :
* Leakage current of noise filter on inverter
input side
Leakage currents of motor during
Igm :
commercial power supply operation
Igi : Inverter unit leakage current
Example of leakage current of
cable path per 1km during the
commercial power supply operation
when the CV cable is routed in
metal conduit
(200V 60Hz)
120
100
8 0
6 0
4 0
2 0
0
2 3.5 8 1422 38 80 150
5.5 30 60 100
Cable size (mm 2 )
Example of leakage current per 1km during
the commercial power supply operation
when the CV cable is routed in metal conduit
(Three-phase three-wire delta
connection 400V60Hz)
120
100
8 0
6 0
4 0
2 0
0
2 3.5 8 1422 38 80 150
5.5 30 60 100
Cable size (mm 2 )
For " " connection, the amount of leakage current is appox.1/3 of the above value.
*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.
10 (Ig +Ign+Igi+Ig +Igm)
1 2
10 {Ig +Ign+Igi
1
+3 (Ig +Igm)}
2
Leakage current example of
three-phase induction motor
during the commercial
power supply operation
(200V 60Hz)
2. 0
1. 0
0. 7
0. 5
0. 3
0. 2
0. 1
1. 5 3. 7 7. 5 1522 37 55
2. 2 5.5 11 18. 5 30 45
Motor capacity (kW)
Leakage current example of three-
phase induction motorduring the
commercial power supply operation
(Totally-enclosed fan-cooled
type motor 400V60Hz)
2. 0
1. 0
0. 7
0. 5
0. 3
0. 2
0. 1
1. 5 3. 7 7. 5 1522 37 55
2. 2 5.5 11 18. 5 30 45
Motor capacity (kW)
(2) Control circuit cable
The cable size of 0.75mm
use with cable other than the main circuit cables, e.g.
operation and signal circuits.
*3 In the connection earthed-neutral system, the
sensitivity current is blunt against an earth (ground)
fault in the inverter output side.
Earthing (Grounding)
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)
[Example]
5.5mm 2
5m
Noise
NV
filter
Inverter
Ig Ign
1
Leakage current Ig
1
Leakage current Ign
Leakage current Igi
Leakage current Ig
2
Motor leakage current Igm
Total leakage current Ig
Rated sensitivity current:
( Ig 10)
*1 Ig +Ign+Igi+Ig +Igm (Unit : mA)
2
1
*2 Ig +Ign+Igi+3 (Igm
1
531
SELECTION
2
or larger is enough for
must conform to
2
5.5mm
50m
3F
IM
200V 2.2kW
Igi Ig Igm
2
Breaker Designed
Standard
for Harmonic and
Breaker
Surge Suppression
5m
= 0.17
33
1000m
0 (without noise filter)
1 (without EMC filter)
Refer to the table below for the
inverter leakage currents
50m
= 1.65
33
1000m
0.18
* 1
3.00 6.65
30 100
+Igm)
2
the
3
* 2