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#1 honeywell


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Posted 10 July 2003 - 08:33 PM

if you fit inverters to an existing installtion what happens to the power factor correction sets that are installed do any filters have to be fitted and if so why?



#2 marke


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Posted 11 July 2003 - 10:44 AM

Hello Paul

It depends on just where the power factor correction is connected.

  • Static correction. Normally connected to either the motor terminals or the output of the starter.
  • Bulk Correction. Usually connected at the main switchboard or submain.

      The induction motor, when driven by and inverter, does not present an inductive load to the supply., therefore it does not need power factor correction. Do Not Connect Power Factor correction to the output of an inverter! You should not connect power factor correction to the input of an inverter either. On the output, the capacitors will cause very high currents to flow through the inverter out put and cause it to fail. On the input, the capacitors will provide a very low impedance energy path and can cause the input rectifier to be damaged by transients. In other words, do not use static correction with an inverter.
      If you have a large plant with automatic bulk correction, there will be additional harmonic currents flowing in the supply from the inverter and these can cause problems with the capacitors in the bulk correction plant. It is prefgerable to fit detuning reactors to the capacitors in the bulk correction unit to reduce the impact of the harmonics on the reliability of the capacitors.
      Best regards,

#3 grobert


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Posted 20 October 2003 - 07:46 PM

Be very carefull. Applications involving power factor correction capacitors and VFD in the same facility can cause big problems. You must contact experts in this field. I would not touch it with a ten foot pole without expert experienced on site guidance.

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