Product Overview

Power semiconductor advances are driving conventional filter technology to obsolescence. Traditional laminated silicon-steel filters are struggling to meet the additional demands required by these devices. CTM Sine Wave Filters do not face the same material and geometric constraints that limit conventional silicon-steel filters. Compared to this conventional technology, CTM Sine Wave Filters offer…

  • EXTENDED SYSTEM LIFE for your AC drive, step-up transformer, and induction motor
  • BETTER MOTOR PROTECTION for motor windings and bearings
  • HIGHER RELIABILITY due to cooler, more efficient filter operation
  • HALF THE SIZE & WEIGHT for a smaller footprint and easier integration and installation

Product Specs

Nominal Operating Voltage:
480 V
Motor Frequency:
6 - 90 Hz (up to 120 Hz with de-rating)
Switching Frequency:
2 - 5 kHz
Estimated Motor HP Range:
100 - 1,200 HP
Current Range:
130 - 1,440 A
Overload Capability:
150% rated current for 1 minute
Maximum Ambient Temperature:
50°C (122°F) (higher with de-rating)
Harmonic Voltage Distortion:
<1.5% with 12% THD input
Insertion Loss (Voltage Drop):
3.3% @ 60 Hz
Motor Cable Length:
15,000 ft or more
Enclosure Options:
Stand-Alone Cabinet (NEMA 3R)
Pedestal Cabinet (NEMA 3R)

The Problem

Variable frequency drives (VFDs) increase motor efficiency by allowing variable speed and torque control of motors. This additional control allows the motor to dial in to an ideal speed for instantaneous demand, thereby increasing efficiency and enhancing performance. VFDs achieve this level of control by using high frequency switching power semiconductors to convert the AC line sinusoidal waveform to a pulse width modulated (PWM) square wave.

However, this conversion process introduces harmonic distortion, voltage spikes (dV/dt issues), and common-mode noise to the voltage signal, which can cause motor stress and heating, common-mode bearing currents (electric fluting), and power losses. All these conditions increase the likelihood of motor failure and reduce the longevity of not only the motor but the entire motor system.

The Solution

When inserted between the AC drive and the motor, SWF Sine Wave Filters protect your motor and other system components. CTM Sine Wave Filters transform the output of variable frequency drives from a square wave with voltage spikes and harmonic distortion to a near perfect sinusoidal waveform. Additionally, CTM Sine Wave Filters are the only sine wave filters with built-in common-mode current mitigation. All this is accomplished in a package that is half the size and weight, operates with twice the efficiency, and carries no additional costs (when compared to conventional technology). The largest companies in the world rely on CTM technology, with more than 200,000 installed units in some of the harshest environments on the planet.



  • Motor Life: Harmful square waves, voltage spikes, high frequency distortion, and common-mode noise are all filtered from the AC drive’s output, reducing motor heating, bearing currents (fluting), and stress, thereby extending motor longevity.
  • Motor Drive Life: CTM filters reduce the VFD workload by 6% or more, significantly extending the drive's life.
  • Filter Reliability: CTM filters maintain lower temperatures, increasing life and reliability.
  • Step-Up Transformer Life: With a fraction of the insertion loss (voltage drop), SWF Sine Wave Filters allow the step-up transformer to operate at a lower voltage ratio, substantially reducing transformer stress.
  • Power Density Our exclusive NEMA 3R Pedestal Cabinet offers the highest power density available on the market.
sinewave filter increases



  • Power Loss: Due to its unique patented design and proprietary materials, CTM Sine Wave Filters operate at higher efficiencies than conventional filter technology, decreasing power loss, minimizing dissipated heat, and reducing total cost of ownership.
  • Electric Fluting (Bearing Current): Common-mode (bearing) current can have disastrous effects on induction motors, leading to electric fluting and premature bearing failure. CTM offers the only sine wave filters with built-in common-mode current mitigation.
  • Design Footprint: At half the size and weight of laminated silicon-steel technology, CTM filters take up less space and are easier to integrate into existing systems.

SWF Line Frequency Sine Wave Filters

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