Hoists supplied by frequency inverters

The frequency inverter allows to modernise the supply and control systems of hoists in an easy way. Thus, it is not necessary to replace the asynchronous hoist engine.

Modernisation examples:

  • removal of start resistances and contactors, installation of frequency inverters
  • replacement of the hoist control system – installation of the PLC with the riding regulator and the speed feedback
  • installation of a transformer for the low voltage frequency inverter
  • replacement of a shaft signalling system

Medium voltage frequency inverter - general view

Power room of a medium frequency inverter

Low voltage frequency inverter - general view

A resistance controlled hoist:

  • high power loss (50%) of the resistances while start-up, slowing and low speed riding
  • low power coefficient and step changes of grid load
  • full range speed and moment control and speed feedback
  • contactors - no reliability

A hoist controlled by a frequency inverter:

  • very low power loss
  • power coefficient - almost 1
  • low harmonics and now step changes
  • full range speed and moment control and speed feedback
  • reliability
  • full diagnostic possibilities.

Medium voltage frequency inverter vs. low voltage frequency inverter

Medium voltage frequency inverter - 6kV

  • replace the resistance control and there is no additional transformer in the system. Moreover, it is not necessary to replace the engine, the 6kV feeder and the electric cables
  • silent work
  • small power module = easy replacement Low voltage frequency inverter - 690V
  • low process voltage



  • full and precise speed regulation
  • compact, full covered, EMC compatibility
  • reliability and full diagnostic system
  • possibility of the remote control implementation Inconveniences
  • Voltage present in the circuit - due to the condensers' batteries
  • new technology


The frequency inverters make the hoist drive control systems similar to the ones of the DC hoists; the supply quality is very high (harmonics, cosφ) - similar to resistance receptors. Hoist control becomes better and the manipulations are safer.


OPA-ROW Sp. z.o.o.
ul. Rymera 40c
44-270 Rybnik


tel. +48(32) 739 88 63
E-Mail: office@opa-row.eu