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Variable frequency drives

291 products, 140 in stock

A variable frequency drive (VFD, frequency inverter) controls the speed of an induction motor: it changes the supply frequency and voltage, provides a smooth start and stop, and reduces the power consumption of pumps, fans and conveyors.

More about variable frequency drives

What a variable frequency drive is

A frequency drive rectifies the mains voltage and then, with power transistors (IGBTs), forms an output voltage with the required frequency and amplitude. The speed of an induction motor is proportional to the frequency, so the drive lets you adjust the speed smoothly from zero to rated speed and above.

Unlike a direct-on-line start, a motor controlled by a drive starts without an inrush current and mechanical shocks. This extends the life of bearings, gearboxes and couplings.

Where they are used

Frequency drives are installed wherever the speed has to be changed or a motor has to start smoothly:

  • pumps and water supply systems — holding the pressure instead of throttling with a valve;
  • ventilation and air conditioning — adjusting fan output;
  • conveyors, mixers, extruders and machine tools;
  • lifting mechanisms, elevators and cranes (with a braking resistor);
  • compressors and refrigeration equipment.

How to choose a drive

The main parameters to look at:

  • Power and current — the rated output current of the drive must not be lower than the motor current; allow a margin for a heavy start.
  • Supply voltage — single-phase 220–240 V (usually up to 2.2 kW) or three-phase 380–480 V.
  • Type of load — fan/pump (variable torque) or constant torque (conveyors, hoists).
  • Control method — scalar (V/f) for simple tasks, vector for accurate torque at low speed.
  • Interfaces — Modbus RTU, Profibus, Profinet, EtherNet/IP for integration with a PLC.
  • IP protection rating — IP20 for a cabinet, IP54–IP66 for mounting outside a cabinet.

New and used frequency drives

The ElectroEU catalog includes both new drives and used equipment. Used drives are tested before dispatch, and the condition of each item is shown on its page. Used equipment is a way to quickly replace a discontinued drive or to save money on non-critical tasks.

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Good to know

How to size a frequency drive for a motor

Start not with kilowatts but with current: the motor nameplate gives the rated current for your connection (star or delta). The output current of the drive must not be lower than this value.

If the load is a heavy start — a loaded conveyor, a crusher, a hoist — choose a drive one frame size larger or a model with a heavy-duty mode that withstands 150% overload for 60 seconds.

For pumps and fans a drive of the same power as the motor is usually enough: the torque at low speed is small, and many models have a separate normal-duty mode with a higher rated current.

Mind the voltage: single-phase 220 V drives give three-phase 220 V at the output, so the motor must be connected in delta (230/400 V). A 400/690 V motor needs a three-phase 380–480 V drive.

Scalar or vector control: which to choose

Scalar control (V/f) keeps a constant ratio of voltage to frequency. It is simple to set up and suits pumps, fans and most conveyors where high speed accuracy is not needed.

Vector control calculates a model of the motor and regulates the magnetic flux and the torque separately. It gives full torque at low speed and holds the speed more accurately when the load changes — important for hoists, winding machines and machine tools.

Most modern drives support both modes. For vector control, always run the autotuning with the motor data from the nameplate.