Mitsubishi Electric FR-A500 Instruction Manual page 45

•
Data line filter
Noise entry can be prevented by providing a data line filter for the detector cable etc.
•
Data examples
By decreasing the carrier frequency, noise will be about as low as
that of our conventional FR-Z200 series.
Noise Terminal Voltage of Inverter and Example
of Its Reduction by Noise Filters
120
100
80
60
20
0
0.1 0.3 0.5
Noise frequency (MHz)
*Noise terminal voltage: Represents the magnitude of noise propagated from the inverter to the power supply.
Example of counter measures against noise
Install filter (FR-BLF,FR-
BSF01) to inverter input side.
Inverter power
supply
Separate inverter and power line
by more than 30cm (11.81 inches)
(at least 10cm (3.94 inches))
from sensor circuit.
Control power
supply
Do not earth (ground) control box directly.
Do not earth (ground) control cable.
By decreasing the carrier frequency, the noise terminal voltage* can be
reduced. Use Pr. 72 to set the carrier frequency to a low value (1kHz).
Though motor noise increases at a low carrier frequency, selection of
Soft-PWM in Pr. 240 will make it unoffending.
Differences between Noise Terminal Voltages
at Different Carrier Frequencies
120
100
80
fc=0.7kHz
60
20
0
0.1 0.3
Conditions
Motor:3.7kW (5HP)
Average terminal voltage 0dB=1µV
120dB=1V
FR-Z220-3.7K
FR-A520-3.7K (fc=0.7kHz)
1 3 5 10
Control box
BLF
Install filter FR-BIF to
inverter input side.
INSTALLATION AND WIRING
Conditions
Motor: 3.7kW (5HP)
Average terminal voltage 0dB=1 m V
FR-A220E-3.7k fc=(14.5kHz)
FR-A520-3.7K
fc=14.5kHz
fc=2.0kHz Soft-PWM(Factory setting)
0.5 1 3 5
Noise frequency (MHz)
By using shielded cables as signal cables, induction noise can be
reduced greatly (to 1/10 - 1/100). Induction noise can also be
reduced by moving the signal cables away from the inverter output
cables. (Separation of 30cm(11.81 inches) reduces noise to 1/2-1/3.)
By fitting the FR-BSF01 or BLF on the inverter output side, induction
noise to the signal cables can be reduced.
Noise Induced to Signal Cables by Inverter Output Cables
100
80
60
40
20
0
10
30
Reduce carrier
frequency.
FR- FR-
Inverter
BLF
FR-
BIF
Power
supply for
sensor
Do not earth (ground) shield but connect
it to signal common cable.
36
120dB=1V
10 30
Conditions
Inverter: FR-A520-3.7K
Motor: SF-JR 4P 3.7kW (5HP)
Parallel cable
Output frequency: 30Hz
Noise form: Normal mode
Twisted pair cable
Inverter
Coaxial cable
FR-BLF
FR-BSF01
(4T)
Measuring instrument
Line-to-line distance, d (cm)
20 30 40 50
Install filter (FR-BLF,FR-BSF01)
to inverter output side.
Use 4-core cable for motor
power cable and use one
cable as earth (ground) cable.
Use twisted pair
shielded cable.
Sensor
5cm
d(cm)
Motor
Terminal
Motor