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VFD Noise

Due to their efficiency and energy savings, VFDs (Variable Frequency Drive) are replacing AC and DC motors in water and wastewater facilities. Unfortunately, VFDs can generate a lot of high frequency noise that can wreak havoc on control and monitoring devices such as PLCs and distributed control systems.  Good shielding and grounding schemes will certainly mitigate these issues but many facilities are quite old and don’t have the adequate time or resources to constantly troubleshoot the sources of common mode noise.

VFD Noise
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If this is a common challenge at your facility consider installing the Class I Div 2, UL approved ECT DIN signal isolator.  The ECT is housed in a rugged RFI/EMI immune case and provides a high level of common mode noise rejection that will filter out the extraneous high frequency noise that is on the 4-20mA signal from the VFD. The ECT is a two wire, output loop powered device and receives its power from the DCS or PLC input card. 

Key Attributes:

  • High common mode noise rejection
  • UL and Class I Div 2 approved
  • Excellent RFI/EMI immunity