Energy efficiency · Motors and drives

Variable frequency drives: run motors only as fast as you need.

Many pumps and fans run at full speed and are throttled with valves or dampers. A variable frequency drive slows the motor instead, and because power falls steeply with speed, the savings can be large.

Diagram of a variable frequency drive controlling an AC motor

How a VFD works

An AC induction motor's speed is set by the supply frequency and its number of poles. A variable frequency drive (also called a variable speed drive) converts the fixed 50 Hz supply into a variable frequency and voltage, so the motor's speed can follow the real demand of the process.

Why speed matters so much

For centrifugal pumps and fans, the affinity laws mean the power needed varies roughly with the cube of speed. Running a fan at 80% speed takes only about half the power of running it at full speed (0.8³ ≈ 0.51). Throttling with a valve or damper, by contrast, wastes much of that energy across the restriction.

Good candidates for a drive

  • Pumps and fans controlled by throttling valves, dampers or bypass loops
  • Air handlers, cooling towers and chilled-water pumps
  • Compressors and process loads with varying demand
  • Conveyors and mixers that don't need full speed all the time

Drives also give a soft start, which reduces mechanical stress and starting current. Because drives are non-linear loads, we check harmonic levels and specify filtering where needed.

Before we recommend anything, a feasibility study measures your site and estimates the saving. After installation, savings are measured and verified to IPMVP and reported monthly.

How we deliver

From measurement to verified savings.

Every measure follows the same process, and can be bought outright, leased or delivered under an Energy Savings Performance Contract with no upfront capital.

  1. Feasibility studyAnalysis of the facility's energy consumption, losses and savings potential.
  2. EngineerTechnical design and a bankable business case covering investment, savings and payback.
  3. FinancingSupport in securing financing, including the documentation lenders require.
  4. ImplementProcurement, installation and commissioning by our own engineers.
  5. VerifySavings measured to IPMVP on our EnMIS platform, reported monthly.
  6. MaintainPreventive maintenance for the full contract term, so that savings are sustained.
FAQ

Frequently asked questions

Which motors benefit most from a VFD?

Variable-torque loads such as centrifugal pumps and fans with long running hours and varying demand. Constant-torque loads gain less from speed reduction.

Do VFDs create harmonics?

Yes, drives are non-linear loads. We assess harmonic levels and include filtering where needed to protect the rest of the installation.

How are VFD savings verified?

We meter the motor before and after the drive is installed and calculate savings to IPMVP, adjusting for changes in operating hours or production.

Energy efficiency
Energy auditsWalk-through and investment-grade audits by an EPRA-licensed Category A audit firm. Voltage optimisationStabilise and reduce supply voltage to what equipment actually needs. Power factor correctionCut reactive power charges and free up transformer capacity. Harmonic filteringActive and passive filters for drives, UPS systems and LED lighting. LED lighting retrofitEfficient LED lighting and controls, manufacturer-neutral. AC and refrigeration optimisationSmarter control of air conditioning, cold rooms and chillers.

Pumps and fans running flat out?

Tell us about your motors and we'll identify where drives would pay back fastest.

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