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4) Harmonic suppression techniques
1.6.8 Inverter-driven 400V class motor
In the PWM type inverter, a surge voltage attributable to wiring constants is generated at the motor terminals.
Especially for a 400V class motor, the surge voltage may deteriorate the insulation. When the 400V class motor is
driven by the inverter, consider the following measures:
z Measures
It is recommended to take either of the following measures.
(1) Rectifying the motor insulation
For the 400V class motor, use an insulation-enhanced motor. Specifically,
1) Specify the "400V class inverter-driven, insulation-enhanced motor".
2) For the dedicated motor such as the constant-torque motor or low-vibration motor, use the "inverter-driven,
dedicated motor".
No. Item Description
1
Reactor installation
(ACL, DCL)
Install a reactor (ACL) on the AC side of the inverter or a reactor (DCL) on its DC side or
both to suppress outgoing harmonic currents.
2
High power factor
converter
(FR-HC)
The converter circuit is switched on-off to convert an input current waveform into a sine
wave, suppressing harmonic currents substantially. The high power factor converter (FR-
HC) is used with the standard accessory.
3
Installation of power
factor improving capacitor
When used with a series reactor, the power factor improving capacitor has an effect of
absorbing harmonic currents.
4
Transformer multi-phase
operation
Use two transformers with a phase angle difference of 30° as in -delta, delta-delta
combination to provide an effect corresponding to 12 pulses, reducing low-degree
harmonic currents.
5
Passive filter
(AC filter)
A capacitor and a reactor are used together to reduce impedance at specific frequencies,
producing a great effect of absorbing harmonic currents.
6Active filter
This filter detects the current of a circuit generating a harmonic current and generates a
harmonic current equivalent to a difference between that current and a fundamental wave
current to suppress a harmonic current at a detection point, providing a great effect of
absorbing harmonic currents.
CAUTION
• If the wiring length between the motor and inverter is 40m or longer, set Pr. 240 to long wiring mode in
addition to the above countermeasures to operate the inverter. (Refer to page 112 for Pr. 240 "Soft-
PWM selection".)