FlowMarket
Where to source frequency converters: FlowMarket is a B2B sourcing network powered by an AI agent. You describe the drive — motor power and current, supply voltage and phases, control mode, overload requirement, braking, EMC class, enclosure and fieldbus — and the AI agent matches you with verified drive manufacturers and distributors, then requests prices, datasheets and lead times from every match at once. Getting matched is free for buyers.
Sourcing frequency converters
A frequency converter, also called a variable frequency drive or inverter, sits between the mains and the motor and synthesises a variable voltage and frequency. Run a pump or fan at 80 percent speed instead of throttling it and the power drawn falls to roughly half, which is why drives pay for themselves in continuous applications faster than almost any other component in the drive train.
Sourcing them well means resisting the temptation to match kilowatts and stop there. Two drives with the same kW rating can differ completely in overload capacity, EMC class and what happens to the energy when the load drives the motor instead of the other way round.
Control modes
V/f (scalar)
Keeps the voltage-to-frequency ratio constant without any model of the motor. Cheap, robust, and entirely adequate for pumps and fans, where torque falls with the square of speed and nothing demands precision. It is also the mode that allows one drive to run several motors in parallel.
Sensorless vector
Estimates rotor flux and position from measured current, giving full torque near zero speed and much better dynamic response. The sensible default for conveyors, extruders, mixers and anything that has to start against a load. Requires a motor identification run at commissioning, which is worth planning for.
Closed loop and specials
- Closed-loop vector — with encoder feedback for precise speed holding and full torque at standstill.
- Servo drives — position control for permanent-magnet motors on dynamic axes.
- Regenerative and active front end — feeds braking energy back to the mains instead of a resistor.
- Decentralised drives — IP66 units mounted on or near the motor, saving cabinet space and cabling.
What to specify when sourcing
These details decide both the part number and the price:
- Motor rating — kW and rated current; current is what actually sizes the drive.
- Supply — 230 V single or three phase, 400 V, 480 V, 690 V, and the mains frequency.
- Control mode — V/f, sensorless vector, closed loop with encoder, or servo.
- Overload — 110 percent for 60 s for pumps and fans, 150 percent or more for constant-torque and heavy starting.
- Braking — none, braking chopper and resistor, or regenerative back to the mains.
- EMC class — C1, C2 or C3 to EN 61800-3, depending on whether the site is residential or industrial.
- Enclosure & cooling — IP20 cabinet, IP55/IP66 wall or motor mount, and cabinet cooling capacity.
- Communication — PROFINET, EtherCAT, EtherNet/IP, Modbus RTU/TCP, or standalone with analogue reference.
- Safety — STO as a minimum, or SS1/SLS to a required PL/SIL level.
- Installation — motor cable length, ambient temperature and altitude, both of which force derating, and quantity.
EMC and motor cable — the part that gets left out of the quote
A frequency converter switches at several kilohertz with edges measured in nanoseconds, and that turns the motor cable into an antenna. Get this wrong and the symptoms show up somewhere else entirely: sensors reading erratically, fieldbus dropouts, an encoder that loses counts. The fixes are not exotic but they must be specified and priced. Use screened motor cable with the screen bonded at both ends over 360 degrees, pick the EMC filter class the installation actually needs, and check the maximum cable length the drive allows — exceed it and the voltage reflection at the motor terminals can approach double the DC link voltage, which is precisely what destroys winding insulation. Long runs need a dV/dt or sine filter. State the cable length in your request; it is the specification most often left out and the one most likely to cause a failure that looks like something else.