Mitsubishi Electric FR-F820-00046 Instruction Manual page 86

Power
supply
 Countermeasures
• 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
To install the earth leakage circuit breaker on 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 14 22 38 80 150
5.5 30 60 100
2
Cable size (mm )
MCCB MC
Inverter
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 1 1 18.5 30 45
Motor capacity (kW)
Thermal relay
Line-to-line static
capacitances
Ig1, Ig2: Leakage currents in wire path during commercial
power supply operation
Ign: Leakage current from noise filters on the input side of the
inverter
Igm: Leakage current from the 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 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.
3. PRECAUTIONS FOR USE OF THE INVERTER
3.1 Electro-magnetic interference (EMI) and leakage currents
Motor
M
Leakage current example of three-
phase 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 1522 37 55
2. 2 5.5 11 18. 5 30 45
Motor capacity (kW)
1
2
3
4
5
6
7
8
9
10
85