The best replacement for vfd is soft start.

The best alternatives to vfd are rated as following:
★★★★★  soft start
★★★★  vsd
★★★  servo
★★  soft starter
★★  pwm
★★  control valve
★★  motor starter
★★  ecm
★  rotary phase converter
★  afd
★  inverter
★  phase converter
★  static phase converter
★  csv
★  rotary converter
★  nixie
★  asd
★  dc motor
★  gearbox
★  inlet vane
★  starters
  igv
  inlet guide vanes
  vector drive
  scr
  starter
  servo drive
  rpc
  cycloconverter
  eddy current

Your alternative for vfd is not listed? Suggest!
Speaking about vfd, one probably shouldn't forget about multiple motors.

Other search terms related to vfd and their ratings are:
★★★★★ multiple motors
★★★ pid control
★★★ star delta bypass
★★ motor
★ pump
compressor
mach3
You have in mind a companion for vfd and it is not yet here? Propose!



Google Trends

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vfd
soft start
vsd