Variable Frequency & Adjustable Speed Drives

Guide to Buying Variable Frequency Drives (VFDs) in the UK: Top Suppliers, Picks, and Buying Tips

Why variable frequency drives matter for your business

If you run motors, pumps, fans, or conveyor systems, VFDs (variable frequency drives) can be the single smartest upgrade you make. They let you control motor speed and torque precisely, cut energy waste, and reduce mechanical wear — think of them as the dimmer switch for industrial motors. Whether you manage a small workshop or a large production line, swapping a fixed-speed starter for a VFD usually pays back fast in energy savings and longer equipment life.

What a VFD actually does — in plain language

A VFD changes the frequency and voltage supplied to an AC motor so you can speed it up or slow it down on demand. Instead of throttling a pump or using belts and gears, you dial in the motor speed. That means smoother starts, less stress on shafts, and lower current draw. Imagine replacing a hammer with a scalpel — more precision, less collateral damage.

Key UK suppliers to consider

There are several trusted suppliers in the UK where you can buy VFDs, spare parts, and accessories. Each has a slightly different focus — some are broad electronics distributors, others concentrate on electrical trade supply, and a few specialise in industrial automation. Good places to start include Expert Electrical, RS Components, Farnell, Screwfix, Cromwell, Rexel, CEF, Rapid Electronics, and specialist motor-control houses. Online marketplaces such as Amazon UK and eBay also list drives, but for industrial installs I usually prefer an authorised supplier or distributor.

Expert Electrical — a store featured in product listings

Expert Electrical appears in many UK product lists and often stocks a range of motor control gear, including starters and drives. If you’ve seen specific items like the Chint NQ3 starter mentioned in catalogues, Expert Electrical is a logical place to check first for availability, technical datasheets, and compatible accessories.

RS Components and Farnell — electronics and industrial distribution

RS Components and Farnell are go-to choices for engineers who want a huge catalogue, datasheets, and fast shipping. They stock major brands such as Siemens, ABB, Danfoss, and Control Techniques, and they’re helpful when you need technical advice, replacement parts, or matching control modules for your drive.

Screwfix, Cromwell and trade suppliers

Trade suppliers like Screwfix and Cromwell are excellent when you need smaller quantities or more basic drives for straightforward mechanical systems. They’re often more competitive on entry-level drives and starter kits for HVAC, pumps, and small motor applications around the workshop or site.

Rexel, CEF and electrical wholesalers

Electrical wholesalers tend to support the trades with competitive pricing, local branches, and the ability to order larger stock. If you’re buying for facilities maintenance, HVAC servicing, or multiple site rollouts, establishing a relationship with a wholesaler such as Rexel or CEF can save time and money.

Featured products to look for

When browsing, you’ll come across models that are perfect for certain jobs. Two items that commonly appear in UK listings are the Chint NQ3 series and legacy items like Sangamo boost controllers. These represent different parts of the market: the NQ3 line is a compact starter/drive solution, while Sangamo covers power-control devices used in water boosting and similar circuits.

Chint NQ3-5.5 — what that model number really means

The Chint NQ3-5.5 starter is often listed with a 110-volt control input and a drive section around 5.5 in metric terms, which is about 7.4 horsepower. It’s a compact choice for single-motor applications where space matters and you need a reliable starter with built-in protections. If your motor is around 7 to 8 hp, this is the kind of unit to consider.

Sangamo electronic boost controller — when to use one

Sangamo devices are typically associated with pump and pressure-boosting applications. A single-button boost controller is ideal for straightforward on/off or single set-point control in domestic or light commercial boosting systems. If you’re managing a pump station that needs simple, dependable pressure control, a Sangamo controller can be cost-effective and easy to install.

How to choose the right VFD for your motor

Picking the right VFD is mostly about matching the drive to the motor and the job. Start by confirming motor horsepower (hp), voltage, and whether you need single-phase or three-phase power. Next, consider the duty cycle — is the motor running continuously at varying speeds or doing short, frequent starts? Those choices influence rated current, overload capacity, and cooling requirements.

Match the horsepower and motor type

Always choose a drive rated for at least the motor’s full-load horsepower. For example, a 7.4 hp motor needs a drive that supports that horsepower and the corresponding full-load amps. Undersizing a drive leads to tripping, overheating, and shortened life.

Check input voltage and phase

Confirm the site supply: common options in UK installations are single-phase 230-volt or three-phase 400-volt supplies. Many smaller drives accept single-phase input and output three-phase to the motor up to certain hp ratings, but larger motors demand three-phase input to match supply capacity and performance.

Rated current and overload capacity

Drives have continuous current ratings and short-term overload ratings (often 150% for 60 seconds, for example). If your application involves frequent heavy starts, choose a drive with a higher overload capability. That prevents nuisance trips and gives headroom for unexpected torque demands.

Installation, wiring and starter compatibility

VFDs are not plug-and-play for every motor. You’ll need to wire them correctly, configure parameters for motor speed and torque, and fit appropriate fusing and isolation. Pay attention to the starter type: some installations still use contactors and fused disconnects for safety isolation even when a VFD is present.

Electrical enclosure and cooling considerations

Make sure the enclosure provides adequate ventilation or cooling. VFDs generate heat, especially under load. If you place a drive in a control cabinet, provide enough clearance and airflow, or select a drive with a forced-air cooling option. In harsher environments, an IP-rated enclosure and filtered cooling are smart investments.

EMI filters and cable routing

Long motor cables can generate electromagnetic interference and reflected waves that stress the motor’s insulation. Use screened cables, follow manufacturer guidance on cable length, and fit EMI filters or dv/dt filters where recommended. Proper earthing and separation from signal cables reduce nuisance interference.

Accessories and add-ons that pay off

Think beyond the drive itself. Encoders, external braking resistors, line reactors, and communication modules (Ethernet/IP, Modbus, ProfiNet) can turn a basic drive into a fully integrated control node. If you plan to monitor performance or integrate with PLCs and building management systems, factor in these costs up front.

Braking resistors and dynamic braking

If your application frequently decelerates a heavy load, dynamic braking or a braking resistor can absorb regenerated energy. Without it, the drive may trip on over-voltage during rapid stops. A properly sized resistor preserves braking performance and prevents costly downtime.

Communication and remote monitoring

Modern drives often include options for network connectivity. Adding a communication card can let you monitor speed, current, and faults remotely — invaluable for predictive maintenance. If you’re managing multiple sites, networked drives are a game-changer for uptime.

Common applications across UK industry

VFDs are everywhere — manufacturing lines, wastewater treatment, HVAC systems, and agricultural pumping. They’re especially valuable where the load changes frequently, or where soft starting reduces mechanical shock. Think of them as a universal gearbox that you control electronically.

Pumps and water boosting systems

Pumps benefit from VFDs because flow and pressure relate non-linearly to speed. Reduce speed a little and you cut energy use significantly. That’s why you’ll often see VFDs paired with pressure transducers in boosting stations and irrigation setups.

Fans, blowers and HVAC

Fans are another perfect match: lowering fan speed reduces power consumption dramatically. VFDs in HVAC let you tune airflow minute-by-minute, improving comfort and cutting energy bills in commercial buildings.

Conveyors and processing lines

In manufacturing, conveyors and belts often need variable speeds to sync processes. VFDs provide smooth ramp-up and ramp-down, reducing product damage and extending mechanical life. They also simplify line balancing when you change product speeds.

Energy savings and return on investment

One of the most compelling reasons to fit a VFD is energy saving. On variable-torque loads such as fans and pumps, a modest drop in speed can slash power use far more than you’d expect. The exact payback period depends on run hours, energy cost, and the load profile, but in many cases the VFD pays for itself in months to a few years.

Safety, standards and certifications to check

Make sure the drive meets applicable standards and carries CE marking where required. Look for manufacturer documentation on thermal protection, short-circuit ratings, and EMC compliance. If your site follows ATEX or other hazardous-area rules, get drives certified to those standards. Safety first: always include lock-off isolation and clear labeling in your control panels.

Buying online versus local distributor — pros and cons

Online retailers often win on price and stock availability; local distributors win on technical support and faster hands-on help. If your installation is complex, a distributor or authorised integrator can verify compatibility, help with parameter set-up, and provide site-specific advice. For straightforward swaps, online ordering from RS, Farnell, Screwfix, or Expert Electrical is convenient and often quick.

Final checklist before you order

Before you hit buy, verify horsepower in hp, input voltage and phase, continuous and peak current ratings, enclosure rating, and any required accessories like filters or braking resistors. Double-check communication options if you plan to network the drive, and make sure spare parts and local support are available. It’s a short checklist that saves headaches down the line.

Where to find technical support and training

Manufacturers typically provide manuals and tuning guides. Many suppliers and distributors offer on-site commissioning, training courses, or online webinars. If you’re new to drives, a short training session can save days of trial and error and dramatically speed up commissioning.

Conclusion

Variable frequency drives are a practical, cost-effective way to control motors and cut energy use. In the UK market you have many options — from trade suppliers like Expert Electrical and Screwfix to large distributors such as RS Components and Farnell. Choose a drive that matches motor horsepower in hp, fits your site’s voltage and phase, and includes the right accessories for braking and filtering. With a little planning and the right supplier, a VFD can improve performance, reduce operating costs, and extend the life of your machinery.