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Sine Wave dv/dt Filters

Sine Wave dv/dt Filters

Sine Wave dv/dt Filters (Type SWF) 200-690 volts, 50/60Hz

APPLICATION: Motors that are controlled by variable frequency drives are subjected to higher stresses and losses caused by PWM voltage and become especially vulnerable to premature failure when the cable lengths between VFD and motor are long. Typical applications include submersible pumps, air handling units, irrigation, municipal water, lift stations, water treatment, etc. Inverter output Sine wave filters can also be used to improve voltage quality from alternative energy inverter power sources.

PWM Inverter to Motor

Type SWF Motor Protection

  • Type SWF Filters

  • Type SWF Filters convert Pulse Width Modulated (PWM) voltage, produced by a typical inverter, to a sine wave without any dv/dt concerns. They eliminate restrictions on cable length, eliminate harmful pulse voltage reflected waves and improve motor performance and life expectancy in AC variable frequency drive installations. APQ offers a complete range of standard filters based upon typical motor full load ampere (FLA) ratings and PWM switching frequency, however, we will gladly produce a customized filter for your exact application requirements.

PWM Inverter

Standard filters are available for PWM switching frequencies of 5kHz and higher,
2-2.5kHz, 4kHz, plus we can produce a filter for any PWM frequency you need.

Typically, motors connected to power systems of 380V and higher are most likely to be exposed to sufficiently high reflected waves that can cause premature failure from peak overvoltage or a high dv/dt rate. The motor protection alternative technique varies depending upon voltage level, cable length and even the voltage pulse rise time (function of the IGBT transistors used in the inverter). However, for protection of submersible motors, it is necessary to use a sine wave filter.

Suggested Motor Filter Application Chart
MotorMotor Cable Length
100 ft300 ft500 ft1,000 ft15,000 ft
230 V motors4-5% Impedance4-5% Impedance4-5% Impedance5% Impedancen/a
400 V motors4-5% Impedance4-5% Impedance5% ImpedanceSWFSWF
460 V motors4-5% Impedance4-5% ImpedanceSWFSWFSWF

APQ Sine Wave Filters are superior to typical dv/dt filters which many times only clamp the harsh PWM voltage instead of returning the voltage to a near sine wave - the voltage the motor was intended to utilize. Our Type SWF filters will eliminate the threat of excessive peak voltage and protect motor windings for any and all cable lengths.