Sine wave filter

Sine wave filter

Sine wave filter theory

Type SWF Sine Wave Fillers utilize passive low pass filter technology to convert inverter Pulse width Modulated (PWM) voltage to a sine wave, They incorporate a unique PWM rated reactor combined with a rugged harmonic rated capacitor to form Filter network that attenuates the PWM inverter switching frequency This filter network removes most of the high frequency content (pulses) from the waveform, resulting in a nearly sine wave output voltage. Motors are protected against dv/dt and excessive peak voltage, and the motor will see normal peak voltage (approximately equal to the DC bus voltage).


Voltage reflection

Voltage reflection is caused when fast rising voltage pulses, such as those produced by PWM inverters, travel on an electrical conductor that is terminated by a high impedance load(motor). The magnitude of the reflected pulse is a function of the characteristic (or surge) impedance of both the cable and motor, The greater the mismatch between motor and cable surge impedance the greater the reflected voltage pulse. The safe distance for the motor cable length is a function of both the impedance mismatch (between motor and cable) and the pulse voltage rise time (IGBT characteristic}. Critical motor cable length is defined in the chart below.


Motor damage

PWM voltage consists of numerous fast rising (high dv/dt) pulses. When motors are located a

long distance( beyond critical cable length as shown in chart) from an inverter, a phenomenon known as voltage reflection occurs, causing the peak voltage at the orator terminals to be as high as 2X the inverter DC bus voltage( nearly 3X system voltage). Most of this excessive peak voltage is impressed upon

the first turns of the motor windings and can cause premature failure. Arteche Type SWF Sine Wave Filters are superior to typical dv/dt filters. Our Type SWF Filters eliminate the threat of excessive peak voltage and protect motor windings for any and all cable lengths.

Circuit diagram

Product specification



System Voltage

208-204,380-415,440-480,550-600 and 660-690 volts

Voltage Tolerance





5-20KHZ(for 5KHZ Types)

2-2.5KHZ(for 2.5KHZ Types)

4-20KHZ(for 4KHZ Types)

any available

Fundamental frequency

5HZ to 90HZ standard, others available on request



Input Current Ratings

3 to 3000 amps

Input power ratings(standard)

1.1KW to 2500KW (1.5HP to 3000HP) typical

Total harmonic voltage distortion

5% THD-v(5KHZ and 4KHZ types) typical

10% THD-v(2.5KHZ types)typical

Reflected voltage at motor

Virtually none

Voltage drop (at rated load)

Optimized for 5% voltage drop at 70% load

Full load drop7%(for 2.5KHZ and 5KHZ types)

Full load drop9%(for 4KHZ types)


99.5% at rated load(typical)

Dielectric strength



Capacitance & Inductance

Capacitance is minimized (and inductance maximized)for lowest capacitor current and lowest dv/dt.

Overload capability

1.5*rated current(1 minute,1time per hour)


Self damping reactors(no power resistors required)

Life expectancy

480,000hours at 50c, rated power



Motor cable length(maximum)



Natural convection(no fans required)

Enclosures available

Indoors, industrial, outdoors, open panels, kits

Ambient temperature

-30c to +50c

Relative humidity

99% non-condensation


3300ft(1000meters) derate for higher altitude



Underwriters laboratories(UL)

Assemblies are UL-508A approved (600v and less)

Components offered in kits are UL component recognized

Complies with UL1531


Complies with EN60289,EN60076-3

CE(Low Voltage Directive)

LVD certificate available

NOTE:Type SWF Filters are intended for use with single motor loads.