Sine Wave Filters

A sinewave filter converts the PWM output of a VFD/inverter into a near-sinusoidal waveform.

Specifications
Voltage Rating	3PH - 400V to 690
Current Rating	2.3 to 1000A
Insulation Class	F Class for dry type (H Class on request)
Overload Capacity	1.5× rated current for 1minute
Cooling	AN/AF
Motor Frequency	0 to 60Hz (Up to 400Hz on request)
Applicable Standards	IEC 60076-6 (power reactors): temperature rise, dielectric, routine/type tests.
Certifications	CE ROHS

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Essential for very long cables / subsea / mines where near-sinusoidal voltage at motor is mandatory
For Non-inverter-duty motors needing true sinusoidal terminal waveform (extend insulation/bearing life)
Supports Multiple motors on one VFD to avoid cross-talk and uneven load sharing
Essential for HVAC/data centers/hospitals to minimize conducted & radiated emissions into sensitive systems
Help Reduce motor heating & acoustic noise for efficiency or comfort-critical sites
Used in Long-distance pump/fan drives to eliminate standing waves and over-voltage entirely
Helps Meet strict EMC/spec mandates (e.g., OEM export packages, naval/rail standards)
Enable standard sine-rated contactors/relays on motor feeders without PWM stress

Sine-Wave Filters — Sizing Notes (Quick Guide)

Purpose: Reconstruct a near-sinusoidal voltage/current so the motor “sees” a sine wave—ideal for very long cables, multiple motors per drive, and non-inverter-duty machines.
When to use: Cable runs >100–150 m, multi-motor feeders, sites with strict EMC/acoustic limits.

What to target

Cut-off frequency (fc): set the L-C low-pass well below the PWM carrier but above fundamental.
Typical: fc ≈ 150–300 Hz (LV), 100–200 Hz (MV).
fc=12πLCf_c = \dfrac{1}{2\pi\sqrt{LC}}fc=2πLC1
Inductance (L): often 5–7% X at fundamental per phase (higher than dV/dt filters).
Capacitance (C): choose so reactive current at 50/60 Hz is acceptable (commonly 3–8% of motor rated current).
Verify inverter can supply leading vars at light load.
Damping (R): include series/parallel damping (or C-type topology) to control peaking and avoid resonance with cable.
Capacitor voltage rating: because of L–C interactions, use elevated LV ratings (e.g., 480–525 V caps on 415 V systems). MV caps per bank spec.
Core choice: Gapped iron-core (compact) or air-core (no saturation, larger footprint).
Thermal/derating: rate for harmonic RMS and ambient; verify audible noise limits.

Spec line (example)

“Sine-Wave Filter, 415 V, 75 A, target fc = 220 Hz, X ≈ 6% @ 50 Hz, L ≈ 0.66 mH/phase, C ≈ 40 µF/phase (Δ), damped, dV/dt ≤ 0.5 kV/µs, THDV_VV at motor ≤ 5%, cable length 300 m, continuous.”

Place filter near the VFD (default). For very long runs, evaluate locating near the motor (case by case).
Keep lead dress short & symmetrical; bond enclosure well to reduce EMI.
Verify inverter carrier and min. load settings recommended by the filter vendor.
Check temperature rise after first run (thermal imaging); re-tighten terminations.