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13 - 86 13. SERVO AMPLIFIERS WI TH A LARGE CAPACITY ( 30k TO 55kW ) 13.9.8 Leakage cu rrent breaker (1) Selection method High-frequency chopper currents controlled by pulse width modulation flow in the AC servo circuits.…

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13 - 85
13. SERVO AMPLIFIERS WITH A LARGE CAPACITY
(
30k TO 55kW
)
13.9.7 Line noise filter (FR-BLF)
POINT
This section explains how to use the line noise filter unique to servo amplifiers
with a large capacity. Other noise reduction products are the same as those
for servo amplifiers with 22kW or less. Refer to section 11.17.
This filter is effective in suppressing noises radiated from the power supply side and output side of the
converter unit, drive unit and also in suppressing high-frequency leakage current (zero-phase current)
especially within 0.5MHz to 5MHz band. The filters are used with the converter power supply wires (L
1
L
2
L
3
)
and drive unit power wires (U
V W).
(1) Usage
Pass the 3-phase wires through four line noise filters. When using the line noise filters with the power wires,
passing the power wires together with the ground wire will reduce the filter effect. Run the ground wire
separately from the power wires.
Use four FR-BLFs.
(2) Outline drawing
[Unit: mm]
160
180
130
85
8
0
2
.
3
3
5
3
1
.
5
7
7
13 - 86
13. SERVO AMPLIFIERS WITH A LARGE CAPACITY
(
30k TO 55kW
)
13.9.8 Leakage current breaker
(1) Selection method
High-frequency chopper currents controlled by pulse width modulation flow in the AC servo circuits.
Leakage currents containing harmonic contents are larger than those of the motor which is run with a
commercial power supply.
Select a leakage current breaker according to the following formula, and ground the drive unit, servo motor,
etc. securely.
Make the input and output cables as short as possible, and also make the grounding cable as long as
possible (about 30cm) to minimize leakage currents.
Rated sensitivity current
10 {Ig1 Ign Iga K (Ig2 Igm)} [mA] ···································· (13.2)
K: Constant considering the harmonic contents
Ign
Noise filter
Cable
Ig1
NV
Converter
unit
Drive
unit
Cable
Iga
Ig2 Igm
M
Leakage current breaker
K
Type
Mitsubishi
products
Models provided with
harmonic and surge
reduction techniques
NV-SP
NV-SW
NV-CP
NV-CW
NV-HW
1
General models
BV-C1
NFB
NV-L
3
Ig1: Leakage current on the electric channel from the leakage current breaker to the input terminals of the drive
unit (Found from Fig. 13.3.)
Ig2: Leakage current on the electric channel from the output terminals of the servo amplifier to the servo
motor (Found from Fig. 13.3.)
Ign: Leakage current when a filter is connected to the input side (4.4mA per one FR-BIF or FR-BIF-H)
Iga: Leakage current of the drive unit (Found from Table 13.7.)
Igm: Leakage current of the servo motor (Found from Table 13.6.)
Table 13.6 Servo motor’s leakage current
example (lgm)
Table 13.7 Converter unit
drive unit's leakage
current Example (Iga)
Servo motor power
[kW]
Leakage current
[mA]
Converter unit
Drive unit
Leakage current
[mA]
30 to 55 2.5 All series 5
120
100
80
60
40
20
0
2
3.5
5.5
8
14
22
38
80
150
30
60
100
Leakage current [mA]
Cable size [mm
2
]
120
100
80
60
40
20
0
2
3.5
5.5
8
14
22
38
80
150
30
60
100
Leakage current [mA]
Cable size [mm
2
]
a) 200V class b) 400V class
Fig.13.3 Leakage current example (lg1, lg2) for CV cable run in metal conduit
13 - 87
13. SERVO AMPLIFIERS WITH A LARGE CAPACITY
(
30k TO 55kW
)
(2) Selection example
Indicated below is an example of selecting a leakage current breaker under the following conditions.
22mm
2
5mm
M
NV
Ig1 Ig2 Igm
Converter
unit
Drive
unit
Servo motor
30mm
2
5mm
Iga
Use a leakage current breaker designed for suppressing harmonics/surges.
Find the terms of Equation (13.2) from the diagram.
Ig1 = 95
1000
5
= 0.475 [mA]
Ig2 = 105
1000
5
= 0.525 [mA]
Ign = 0(not used)
Iga = 5 [mA]
Igm = 2.5 [mA]
Insert these values in Equation (13.2).
Ig
10 {0.475+0+5+1 (0.525+2.5)}
85 [mA]
According to the result of calculation, use a leakage current breaker having the rated sensitivity current (Ig)
of 85[mA] or more. A leakage current breaker having Ig of 200[mA] is used with the NV-SP/SW/CP/CW/HW
series.