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2.4. Application of LC filter
2.4.1. Role of LC Filter
LC filter reduces the load applied to the DC motor by smoothing the PWM control waveform (average voltage
control of the pulse width modulation by using square wave) which is output from VF66B (DC motor drive) and
reducing the peak voltage applied to the DC motor. Because the application of LC filter varies depending on
the structure of DC motor and the deterioration state of insulation,
please contact us.
2.4.2. Power Constant Operation
When performing the power constant operation, please install the specified LC filter between the output of
VF66B (DC motor drive) and the DC motor. Input the voltage after LC filter to the field amplifier for weaker
field control. For how to connect the voltage input to the field amplifier, refer to "2.3 How to Connect the
Printed Control Board [VFC66-Z] and Field Amplifier" in Chapter 2.
2.4.3. Selection of LC Filter
Following L (DC reactor) and C (film capacitor) are provided. Select the number of LC filters depending on the
current of DC motor and apply them in parallel.
L1 (DC reactor) 3 mH 115 A
L2 (DC reactor) 15 mH 25 A
C (Film capacitor) 400
μ
F 800 V
Selection example
For DC motor, 200 kW, 440 V, 489 A, 1150 min
-1
:
DC motor current/DC reactor rated current = 489/115 =4.25
By rounding up the first decimal number, you get "5." Therefore, apply 5 pieces of L and 5 pieces of C in
parallel.
The following table indicates the resonance frequencies.
L C
Resonance
frequencies
L1 3 mH
400
μ
F 145
Hz
L2 15 mH
400
μ
F
65
Hz
L2 15 mH 2 parallel (7.5 mH)
400
μ
F
92
Hz
L2 15 mH 3 parallel ( 5 mH)
400
μ
F 112
Hz
VF66B
(DC motor
drive)
N
P
LC filter
M
3 mH,115 A
400
μ
F,
800 V
200 kW,
489 A
Field amplifier
