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Dukane RFI Filter for Ultrasonic Plastic Welders

Dukane RFI Filter for Ultrasonic Plastic Welders

Dukane is a global provider of ultrasonic plastic welders for thermoplastic materials. Our welding equipment is designed with a high quality RFI power line filter to meet FCC and CE requirements for conducted emissions. The RFI (Radio Frequency Interference) is an unwanted noise generated by a wide variety of electronic and electrical devices. Ultrasonic welders which generate unwanted radio frequency energy greater than 10 kHz must comply with the government and safety agency requirements. The RFI is the radiation or conduction of radio frequency energy (or electronic noise) produced by electrical and electronic devices at levels that interfere with the operation of adjacent equipment. Frequency ranges of most concern are 10 kHz to 30 MHz for conducted emission and 30MHz to 1 GHz for radiated emission.

Most electrical and electronic equipment can produce RFI noise. The most common sources include components such as switching power supplies, relays, motors, triacs and equipment such as personal computers, printers, medical instrumentation, industrial controls and electronic games. An electrical and electronic device emits RFI in two ways: a) radiated RFI is emitted directly into the environment from the equipment itself; b) conducted RFI is released from components and equipment through the power line cord into the AC power line network. This conducted RFI can affect the performance of other devices on the same network.

Radiated RFI is usually controlled by providing proper shielding in the enclosure of the equipment. Conducted RFI can be attenuated to satisfactory levels by including a power line filter in the system. The filter suppresses conducted noise leaving the unit, reducing RFI to acceptable levels. It also helps to lower the susceptibility of the equipment to incoming power line noise that can affect its performance. Since no electronic equipment operates in total isolation, manufacturers must protect their own equipment from RFI noise produced by other devices functioning in close proximity or on the same power line. They are also responsible for making sure that their equipment does not transmit offending RFI noise, resulting in the malfunction of other devices.

RFI power line filter consisting of a multiple-port network of passive components arranged as a dual low-pass filter, attenuates radio frequency energy to acceptable levels, while permitting the power frequency current to pass through with little or no attenuation. Their function, essentially, is to trap noise and to prevent it from entering or leaving equipment. RFI is conducted through a power line in two modes. Asymmetric or common mode noise occurs between the line and ground. Symmetric or differential mode is measured from line to line. Common Mode: Also known as line-to-ground noise is measured between the power line and ground potential. Differential Mode: Also known as line-to-line noise is measured between the lines of power. Power line filters are designed to attenuate either one or both modes of noise. The need for one design over another will depend on the magnitude of each noise type present. The attenuation is measured in dB (decibels) at various frequencies of signal.

Dukane power line RFI filters are designed to meet both FCC and CISPR 11 with 5dB to10dB below the limit. They are generally built with three-pole filter networks to meet greatly varying electromagnetic environments for medical electronic and industrial control equipments.

The governments and safety agencies of major industrial countries, including the United States, Canada, and the European Union have established noise emission regulations that are focused on digital and other electronic equipment. The most important guidelines for an Ultrasonic Welder are FCC CFR 47 (Parts 18) in the United States and CISPR 11 in the European Union.

FCC CFR 47 (Part 18) Industrial, Scientific, and Medical equipment (ISM), for Ultrasonic equipment. A category in which the RF energy is used to excite or drive an electromechanical transducer for the production of sonic or ultrasonic mechanical energy for industrial, scientific, medical or other none communication purposes.

The European Union has also harmonized the national regulations and has established the international standard CISPR 11(EN55011) which covers conducted emission for Industrial, Scientific and Medical (ISM) radio frequency equipment.

The following tests were performed to determine that Dukane Ultrasonic products are in compliance with the council of Europe and technical specifications of the EMC Directive 2004/108/EC, Low Voltage Directive 2006/95/EC and Machinery Directive 2006/42/EC.

  • EN 60204-1: Safety of Machinery – Part 1: Specification for General Requirements.
  • EN 12100-1&2: Safety of Machinery – Basic concepts, general principles for design.
  • ISO 13854: Minimum gaps to avoid crushing of parts of the human body.
  • EN 61000-6-2 and EN 61000-6-4_Generic Emission & Immunity:
  • EN 55011: Conducted Emissions – 150 kHz to 30 MHz
  • Radiated Emissions – 30 MHz to 1GHZ
  • EN61000-4-2: Electrostatic Discharge (ESD) 4kV (contact), 8kV (air)
  • EN61000-4-3: Radiated Radio Frequency Immunity – 80 MHz to 1000 MHz
  • EN61000-4-4: Electrical Fast Transient Immunity
  • EN61000-4-5: Surge Immunity
  • EN61000-4-6: Conducted Immunity – 150 kHz to 80 MHz
  • EN61000-4-8: Magnetic Field Immunity
  • EN61000-4-11: Voltage Dips, Short Interruptions and Voltage Variation Immunity


  • Attenuation: The decrease in intensity or absorption of electromagnetic energy. Expressed in dB.
  • Conducted Interference: Electromagnetic signals entering a device through direct connection.
  • b: The level of electromagnetic disturbances equipment can cause to its environment.
  • Filter: Removes electrical noise or interference from the power line by cleaning up the sine wave.
  • Immunity: The level to which equipment is immune to electromagnetic disturbances in its environment
  • Impedance: Opposition to the flow of electrical current when a given voltage is applied.
  • Inductor: Passive component that produces a voltage proportional to the change in current. Measured in Henrys.
  • Insertion Loss: The electromagnetic signal loss resulting from the insertion of a filter in a transmission line. Expressed in dB.