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Reducing Wiring's Acoustic Noise When Using a SCR DC Drive

December 2002

What is the source of the noise?
  • The AC input lines to the isolation transformer/transformer itself? 
  • The DC lines to the motor? 
  • The motor? 

If hum is from the AC lines:
Assuming the transformer is also in the machine room with the drive, a three phase harmonic trap filter made specifically for SCR type drives would be the best choice. It must be placed between the transformer primary and the utility feeder, and located in the machine room to isolate harmonic currents from entering the long AC feeder lines.

If hum is from the DC lines:
  • The DC feeder lines were designed to handle dc current from a motor/generator, not a rectifier type power converter. 
  • The metal wireway or buss bar hardware may "rattle" due to the 360 HZ ripple current frequency inherent in the DC output of a SCR type DC Drive.
  • Is there a Ripple Filter*? Where is it? It should be close to the drive, not remotely mounted near the motor.
  • If there is none, get one, and mount it close to the drive. Adding inductance is about the only way to reduce ripple out of a solid state DC Drive.
  • Install the Ripple Filter close to the drive to minimize ripple current in the filter-to-motor feeder lines. You want to keep DC lines shortest where ripple currents are highest.

If hum is from the motor:
Magnetek DSD 412 Application Note, "Using a Ripple Filter with the DSD 412 Elevator Drive"


*Refer to Magnetek DSD 412 Application Note, "Using a Ripple Filter with the DSD 412 Elevator Drive" for proper set-up of a Ripple Filter.

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