What is RFI (EMI) / EMC?
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.
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.
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 filters
RFI filters are available as feedthrough components, or as PCB filters, IEC inlet filters and power entry modules, single phase filters, 3-phase filters, 3-phase and neutral line filters, output filters, EMC/EMI chokes and pulse transformers.
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 as follows:
1. Single Phase RFI Filters - 240VAC
- Single Stage Circuit
- Two Stage Circuit
- Three 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.
Power quality audits can be carried out on your site by Fuseco's expert Power Quality team to assess your Harmonic Mitigation needs. A report will be presented to you outlining the results and any recommendations on solutions that may be needed for your electrical system to comply with acceptable harmonic levels outlined in IEEE 519.
Depending on the specific situation, there are a variety of products that are used to mitigate harmonics or reduce the effects of RFI. Fuseco's PQ Consultants are more than happy to assist in providing advice on your particular needs.
How can I find out more?
Schaffner have released an information booklet called "Basics in EMC & Power Quality".