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Mitsubishi Electric FR-CS84-012 Instruction Manual Page 50

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Power
supply
 Countermeasure
• Use Pr.9 Electronic thermal O/L relay.
• If the carrier frequency setting is high, decrease the Pr.72 PWM frequency selection setting.
Note that motor noise increases. Selecting Pr.240 Soft-PWM operation selection makes the sound inoffensive.
To ensure that the motor is protected against line-to-line leakage currents, it is recommended to use a temperature sensor
to directly detect motor temperature.
 Installation and selection of the molded case circuit breaker
Install a molded case circuit breaker (MCCB) on the power receiving side to protect the wiring at the inverter input side. Select
an MCCB according to the inverter input side power factor, which depends on the power supply voltage, output frequency and
load. Especially for a completely electromagnetic MCCB, a slightly large capacity must be selected since its operation
characteristic varies with harmonic currents. (Check it in the data of the corresponding breaker.) As an earth leakage current
breaker, use the Mitsubishi earth leakage current breaker designed for harmonics and surge suppression.
 Selecting the rated sensitivity current for the earth leakage circuit
breaker
When using an earth leakage circuit breaker with the inverter circuit, select its rated sensitivity current as follows, independently
of the PWM carrier frequency.
• Breaker designed for harmonic and surge suppression
Rated sensitivity current
I∆n ≥ 10 × (Ig1 + Ign + Igi + Ig2 + Igm)
• Standard breaker
Rated sensitivity current
I∆n ≥ 10 × {Ig1 + Ign + Igi + 3 × (Ig2 + Igm)}
Example of leakage current of
cable path per 1km during the
commercial power supply operation
when the CV cable is routed in
metal conduit
(200 V 60 Hz)
120
100
8 0
6 0
4 0
2 0
0
2 3.5
8 1422
38
80
150
5.5
30
60
100
2
Cable size (mm )
Example
2
2
5.5mm
×5m
5.5mm
ELB
Noise
filter
Inverter
Ig1
Ign
Igi
MCCB
MC
Line-to-line leakage currents path
Leakage current example of
three-phase induction motor
during the commercial
power supply operation
(200 V 60 Hz)
      
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)
×50m
Leakage current Ig1 (mA)
Leakage current Ign (mA)
M
200V2.2kW
Leakage current Igi (mA)
Ig2
Igm
Leakage current Ig2 (mA)
Motor leakage current Igm (mA)
Total leakage current (mA)
Rated sensitivity current (mA) (≥ Ig
× 10)
Thermal relay
Inverter
Line-to-line static
capacitances
Ig1, Ig2: Leakage currents in wire path during commercial power
supply operation
Ign: Leakage current of inverter input side noise filter
Igm: Leakage current of motor during commercial power supply
operation
Igi: Leakage current of inverter unit
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 400 V 60 Hz)
120
100
8 0
6 0
4 0
2 0
0
2 3.5
81422
38
80
150
5.5
30
60
100
2
Cable size (mm )
For " " connection, the amount of leakage current is appox. 1/3 of the above value.
Breaker designed
Item
for harmonic and
surge suppression
33 ×
1000m
0 (without noise filter)
1
50m
33 ×
1000m
0.18
3.00
30
3. PRECAUTIONS FOR USE OF THE INVERTER
3.1 Electro-magnetic interference (EMI) and leakage currents
Motor
M
Leakage current example of threephase
induction motor during the
commercial power supply operation
(Totally-enclosed fan-cooled
type motor 400 V 60 Hz)
2.0
1.0
0.7
0.5
0.3
0.2
0.1
1.5 3.7
7.5
15223755
2.2
5.5
1 1
18.5
3045
Motor capacity (kW)
Standard breaker
5m
= 0.17
= 1.65
6.66
100
1
2
3
5
5
6
7
8
9
10
49

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