What is a Variable Speed Drive?

Variable speed drives (VSDs) and other high-efficiency products are industrial electric motors where the speed can be adjusted by an external controller to make significant savings in energy usage.

How Does a Variable Speed Drive Work?

VSDs work like a ‘dimmer switch’ – they automatically reduce the speed of a motor when it is not busy. They can drastically reduce the amount of energy used in refrigeration, pumps, ventilation fans, air compressors etc.

Variable Speed Drives in the UK

Every year, several more million VSD motors are added. They are the workhorses of UK industry, driving machines, compressors, fans, pumps and conveyors in virtually all industrial sectors.

They also have the greatest energy-saving potential.

Benefits of VSDs

  • Energy savings
  • Increase profitability
  • Control over the drive
  • Fewer mechanical failures
  • Increase motor longevity
  • Reduced risk of motor damage during start up and stop

Did you know?

Using a VSD to slow down a fan or pump motor from 100% to 80% can save as much as 50% on energy use with payback as short as six months?

VSD Application and Savings

Vast Range of Applications

VSDs can be applied in the widest range of settings, across many sectors. Some recent success stories are in food, airports, education, railways, laundry, mining and manufacturing.

Meeting needs, cutting costs

Many pumps are oversized or poorly matched to current process needs – this problem is solved with variable speed drives that adjust the speed of the motor to match the exact production needs and so save energy.

Make Savings from Month One

An average electric motor consumes its purchase price in electricity in just one month (30 days) so investing in the highest efficiency variants gives an ongoing saving from month one.

Benefits of Upgrading VSDs

New VSDs also bring big savings compared with older VSD technologies, due to improvements in switching topologies, and quite often 15% savings compared to older models can be realised.

The motor control is also far smoother and so mechanical parts, belts and seals are not damaged during running, which reduces maintenance costs.

Motor Speed Savings

Motor speed control offers UK industry the single largest opportunity for saving energy and money.

Most motors run at a fixed speed. By adjusting the speed to more accurately match the requirements of the loads, which generally vary over time, you can enhance the efficiency of motor drive equipment.

The benefits of motor speed variation can include increased productivity and product quality, less wear and mechanical stress, power factor correction (cos phi; close to 1) and noise reduction along with energy savings of 50% or even more for some types of applications.

Pump and Fan Energy Savings

One of the most effective ways to save energy is to target your pump and fan applications because there are so many of them and the potential energy savings are so great.

Fan and pump applications are known as “variable torque” and in a variable torque load the power changes with the cube of the speed, for just a 7% speed reduction (that equates to 3.5Hz on a 50Hz system) the energy saving would be 20%, for a 20% speed reduction (10Hz), the energy saving rises to 50%.

The graph shows the energy use of a fan system with three different control methods. The energy use of the drive closely follows the demands of the system, because this is the only control method that regulates the output in accordance with the system needs.

Both the inlet guide vane and the outlet damper control the output by placing a restriction in the way of the flow, with the motor still running at full speed. By contrast, the drive varies the speed of the motor and only uses the energy needed to achieve the required output. The same principles apply to pump systems.

How Variable Speed Drives Have Improved

Variable speed drive technology has improved significantly over many years.

New switching technologies and switching devices mean new VSDs can be 10 – 15% more efficient than older models, so targeting existing variable speed technologies also has great benefit.

Variable Speed Drive Survey, Supply & Installation

We can provide competitive VSD supply-only pricing or our UK-wide field service team offers full survey, investment-ready proposals, specification of correct ABB product, supply, install and commissioning.

Energy efficiency. A solution.

Watch the video to see how variable speed drives can help in solving the energy challenges we all face.

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