Types of Filters

  • Also known as Inductors, Chokes & Line Filters.
  • For use on the input of a VSD / Inverter or other non-linear devices.
  • Virtually eliminate nuisance tripping.
  • Extend life of semiconductors.
  • Reduce harmonic distortion.
  • Reduce surge currents.
  • Improve true power factor.



3.dV/dT filters

  • dV/dT filters are designed to protect AC motors from the destructive effects of long lead peak voltages.
  • Increase bearing life and up-time.
  • Reduce common mode noise and currents.
  • Prevent voltage spikes from exceeding 1kV.
  • Reduction in motor peak voltages.
  • Protection of motor insulation.
  • Reduction of motor temperature.

4. Sine Wave Filters

  • In addition to protecting the motor, the sine-wave filter also provides protection for the VSD/inverter.
  • Unshielded motor cables can be used, lower project costs.
  • Motor operating life is increased.
  • Longer motor cables possible.
  • Significantly lower eddy current and stray flux losses.
  • Significant reduction of bearing currents.
  • Eliminate torque ripple.
  • Eliminate voltage wave reflection.
  • Reduces motor noise, vibration and heat.

5. Passive Filters

  • Also known as 'Low Pass Filters'.
  • For reducing harmonics at the VSD / Inverter or other non-linear devices.
  • Reduction of harmonics to 5-6%
  • Reduce cable heating and line losses.
  • Improve power factor and reduce system loss.
  • Minimize interference with other equipment.
  • Improved system voltage/current waveform.
  • Prevent nuisance tripping of fuse and circuit breakers.
  • Meets the IEEE519 Standard.

6. Active Filters

  • Mainly used for group harmonic compensation at the main switchboard.
  • Reduction of harmonics to 5% or less.
  • Reactive current control.
  • Load side transient suppression.
  • Load side surge suppression. Reduction of supply sags and surges.
  • Improves electrical system efficiency.
  • Reduces operations and maintenance costs.
  • Meets the IEEE519 Standard.

a. What is RFI (EMI) / EMC?
EMI (Electromagnetic Interference) is also called RFI (Radio Frequency Interference). Although the terms EMI and RFI are often used interchangeably, EMI is actually any frequency of electrical noise, whereas RFI is a specific subset of electrical noise on the EMI spectrum. RFI is a disturbance that affects an electrical circuit due to either electromagnetic conduction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, degrade or limit the effective performance of the circuit. The source may be any object, artificial or natural, that carries rapidly changing electrical currents, such as an electrical circuit or the Sun. There are two types of RFI. Conducted RFI is unwanted high frequencies that ride on the AC wave form. Radiated RFI is emitted through the air. There are many pieces of equipment that can generate RFI, variable frequency drives included. EMC (Electromagnetic Compatibility) means nothing more than 'an electronic or electrical product shall work as intended in its environment. The electronic or electrical product shall not generate electromagnetic disturbances, which may influence other product'. In other words, EMC deals with problems of noise emission as well as noise immunity of electronic and electrical products and systems. Electromagnetic disturbances occur as conducted interference as well as radiated emissions and immunity problems.

b. What are the effects of RFI in your electrical system?
If you are occasionally experiencing interference with your telephone system, flickering computer monitors, reliability issues with computer networks, instrumentation errors, or misbehaving electronics you are most likely experiencing RFI in your electrical environment. RFI can wreak havoc with your electronics, computers and telephones, making your workplace difficult to work in. Since most machines have control electronic circuits, they may become difficult to control or unreliable.

c. How do you reduce the effects of RFI?
Depending on your application, there are many ways to reduce the effects of RFI. For conducted RFI, you can choose from a large range of RFI filters, chokes & pulse transformers. For radiated RFI, you can choose from a large range of shielding products.

What are the different types of RFI ?
1. Single Phase RFI Filters - 240VAC

  • Single Stage Circuit
  • Two Stage Circuit
  • Three Stage Circuit

1. Single Stage Circuit
This range of RFI filters are used to attenuate EMI in 240VAC single phase electrical systems. The single stage circuit is ideal for general applications. The two stage circuit is ideal for applications where higher attenuation is required (very noisy environments). The three stage circuit is ideal for applications where the highest possible attenuation is required (eg. military applications).

2. Three Phase Filters (3 Wire) - 440VAC, 480VAC, 520VAC, 690VAC
This range of RFI filters are used to attenuate EMI in 440VAC, 480VAC or 520VAC three phase electrical systems. Common applications include variable speed drives (VSD's), mining, pumping, refrigeration, HVAC and industrial.

3. Three Phase + Neutral Filters (4 Wire) - 440VAC, 480VAC, 520VAC
This range of RFI filters are used to attenuate EMI in 690VAC three phase electrical systems which require a neutral connection. Common applications include variable speed drives (VSD's), mining, pumping, refrigeration, HVAC and industrial.