Variable Frequency Drives

What is a Variable Frequency Drive (VFD)?

A variable frequency drive (VFD) — also called a variable speed drive (VSD) or inverter — is an electronic controller that changes the speed of a standard AC induction motor by varying the frequency and voltage of the power fed to it. Left on mains power, an AC motor runs at a near-fixed speed set by the 50Hz supply frequency and the number of motor poles. A VFD sits between the incoming supply and the motor: it converts the incoming AC to DC, then re-synthesises it as a variable-frequency output using pulse-width modulation (PWM), so motor speed and torque can be dialled to match what the process actually needs rather than running flat out and being throttled mechanically. Not sure which one suits your job? Our DOL vs Star-Delta vs Soft Starter vs VFD: How to Choose a Motor Starting Method covers selection in detail.

That control brings three practical benefits. On variable-torque loads like centrifugal pumps and fans, power draw falls roughly with the cube of speed — so trimming speed with a VFD instead of throttling a valve or damper cuts energy use far faster than it cuts flow. A VFD also soft-starts the motor, ramping current up gradually instead of the hard inrush of direct-on-line (DOL) starting, which reduces mechanical shock on couplings, belts and bearings and avoids the voltage dip a big DOL start can put on a site's supply. And because the drive constantly monitors current and can be parameterised for the motor's protection class, it doubles as an electronic motor overload and fault-trip device.

VFDs turn up wherever an AC motor's speed needs to track a variable process: pumps and fans matching flow to demand, conveyors setting line speed, mixers and agitators, compressors, and any machine where a hard DOL start is undesirable. If all you need is a gentler start with no ongoing speed control, a soft starter is the cheaper option — see the FAQs below for how to tell the two apart.

What's in the AIMS Industrial VFD range

AIMS Industrial stocks the Invertek TECDriveAC and TTA variable frequency drive series — five drives covering 0.37kW through to 160kW, in single-phase 240V and three-phase 380–480V input, IP20 panel-mount and IP66 washdown/outdoor-rated enclosures.

All five carry a built-in EMC filter as standard, Modbus RTU and CANopen communications on board, and are rated for continuous operation in ambient temperatures up to 50°C. The TECDriveAC E3 and the single-phase 240V I/O model add Bluetooth connectivity, sensorless vector control, a built-in PI controller and brake chopper, and application macros that switch the drive between Industrial, Pump and Fan operating modes — commissioning runs off just 14 basic parameters. Their internal EMC filter is rated Internal C1 category to EN 61800-3:2004. The two IP66 models are built with a sealed ABS enclosure and a corrosion-resistant, UV-stable polycarbonate housing rated for high-pressure washdown and outdoor exposure down to -20°C without becoming brittle; the switched TTA E3 IP66 adds an inbuilt potentiometer so a technician can wire it up and dial in speed on the spot.

How to choose a VFD

Sizing starts with the motor you're driving, then works outward to the installation:

• Match kW to the motor. The drive's continuous kW rating should meet or exceed the motor's shaft kW from the nameplate. For high-inertia or high-overload starts, talk to us about sizing a frame up.
• Match the input supply. Small single-phase 240V sites need a single-phase-input drive (the TECDrive Single Phase 240V I/O covers 0.37–1.1kW; the TECDriveAC E3 and TECDrive/TTA E3 IP66 also take single-phase input up to 2.2kW). Anything larger, or any three-phase site, runs on the three-phase 380–480V input variants — which is the only input the TTA P2 range (0.75–160kW) accepts.
• Match the enclosure to the environment. IP20 drives are open-frame and belong inside a switchboard or control panel that provides the environmental seal. IP66 drives are dust-tight and washdown-rated for direct mounting on the machine itself — the right call for food and beverage washdown duty, dusty extraction fans, or an outdoor pump station, because it removes the cost and heat-soak issue of a separate enclosure.
• Decide if you need local isolation. The switched TTA E3 IP66 has a built-in mains isolator and speed potentiometer at the drive — useful where a technician needs to isolate and adjust speed without going back to a separate switchboard.
• Confirm the control interface you need. All five ranges run Modbus RTU and CANopen as standard for PLC or SCADA integration; the TECDriveAC E3 and single-phase I/O models add Bluetooth for setup from a phone, and the TTA P2 range takes pluggable I/O, encoder and fieldbus modules for more advanced control.

Connecting supply and motor cables, configuring drive parameters and commissioning a VFD is electrical work under the AS/NZS 3000 wiring rules — it needs to be carried out by a licensed electrician.

Brand — who we stock

Every drive in this range is supplied by Invertek, the only VFD brand AIMS Industrial currently carries. It's a deliberately narrow range rather than a padded one: five drives that cover single-phase workshop pumps right through to 160kW three-phase process drives, all built on the same TECDriveAC/TTA platform so parameters, keypad and commissioning steps carry across the range. Browse the full Invertek brand range if you'd like to see all five side by side.

VFDs pair with

A VFD is one half of a variable-speed motor package — the other half is the motor it's driving and the mounting hardware around it. See our electric motors range, or go straight to three-phase electric motors or single-phase electric motors depending on your supply. Where the application needs a mechanical brake as well as speed control — hoists, positional stopping — see brake motors.

VFDs — common questions

What's the difference between a VFD and a soft starter?

A soft starter reduces the current spike at motor start-up but doesn't control speed once the motor is running — it's a cheaper option when all you need is a gentler start. A VFD does everything a soft starter does at start-up, plus continuous speed control while the motor runs. If your application only needs a soft start (a large compressor or fixed-speed conveyor, say), a soft starter is the more cost-effective choice; if speed needs to vary with load — pumps, fans, process lines — the VFD's energy savings and control flexibility pay for the extra cost.

How do I size a VFD to my motor?

Match the drive's continuous kW rating to the motor's shaft kW as shown on its nameplate, then check the supply voltage and phase line up (single-phase 240V or three-phase 380–480V) and that the drive's rated output current covers the motor's full-load current. For loads with a heavy or frequent starting duty — high-inertia fans, positive-displacement pumps — it's worth checking whether the next frame size up is the safer choice, since an undersized drive can nuisance-trip under load.

Do I need an IP20 or an IP66 drive?

IP20 drives are open-frame and need to be mounted inside a switchboard or control panel that provides the dust and moisture seal — that's the lower-cost option for a protected indoor installation. IP66 drives are fully sealed and rated for washdown and outdoor exposure, so they can be mounted directly on the machine without any separate enclosure — the right call for food and beverage processing, dust extraction, or an outdoor pump station.

Can I run a VFD from single-phase power?

Yes, provided it's a single-phase-input drive. The TECDrive Single Phase 240V I/O is built specifically for single-phase 240V sites (0.37–1.1kW), and the TECDriveAC E3, TECDrive E3 IP66 and switched TTA E3 IP66 all take single-phase 240V input up to 2.2kW as well as three-phase. The TTA P2 range (0.75–160kW) is three-phase input only, since it covers the larger end of the range where single-phase supply isn't practical.

How much energy does a VFD actually save?

It depends on the load. Centrifugal pumps and fans follow the affinity laws — their power draw falls roughly with the cube of speed — so a VFD trimming speed to match demand instead of throttling a valve or damper delivers a real, often substantial, reduction in running cost. A motor that already runs at full, constant speed with no throttling or intermittent duty won't see the same payback, since the drive's own conversion losses are added with no speed reduction to offset them. The saving comes from matching speed to a genuinely variable load, not from the drive itself.

What's the difference between the non-switched and switched TTA/TECDrive models?

Non-switched drives are wired directly to a separate isolator or switchboard. The switched TTA E3 IP66 has a mains isolator switch and a speed-setting potentiometer built into the drive itself, so a technician can isolate the drive and set speed on the spot without additional switchgear — useful on machine-mounted installations in harsh or washdown environments.

What's the biggest drive AIMS stocks, and what does it add over the smaller ranges?

The TTA P2 range runs from 0.75kW up to 160kW three-phase — the only range in this line-up above 37kW. It adds a TFT display, DIN-rail mounting, a contactor-style power wiring arrangement, and pluggable modules for I/O, encoder and additional fieldbus protocols, which suit larger process drives on conveyors, crushers, extruders, mixers and similar demanding equipment.

Need help sizing a VFD, matching it to a motor, or specifying the right enclosure for your environment? Contact our team — we're happy to work through it with you.