What is a variable frequency drive?
What is a "VFD" Variable Frequency Drive?
What is a variable frequency drive?
You could say, a VFD is the best friend of your electric motor. Variable frequency drives (VFDs) are intelligent control devices that ensure efficient operation of electric motors, to use less energy and reduce operating costs. At the same time, they extend equipment lifetime, optimize processes, and reduce maintenance requirements.
Did you know a VFD can help you to save on your energy bill? The VFD can dramatically reduce energy consumption when compared to direct-on-line (DOL) operation, where the motor runs at full speed regardless of the demand. Using a drive, power or fuel savings of 40% are common. Sometimes the savings are as much as 80%. The roll-on effect means that use of drives also reduces NOx emissions and CO2 footprint of the systems in which they are installed.
When you understand what a VFD is and how to use it, you can get closer to reaching your climate targets, as well as winning competitive advantage. That’s why a VFD is a great asset and friend – not only to your motors, but your whole business.
Key benefits of VFDs:
VFDs for energy efficiency: VFDs intelligently control motor speed, significantly reducing energy consumption (often 40%+) compared to running motors unregulated, at full speed
Cost savings and fast return on investment (ROI): VFDs lower energy bills, reduce maintenance, and improve process control, with a typical ROI of 6-12 months
Versatile applications: VFDs and power converters optimize diverse applications, including fans, pumps, conveyors, cranes, marine propulsion, hydrogen electrolysis, and renewable energy systems
Beyond energy savings: VFDs offer benefits beyond energy savings, such as improved performance, enhanced process control, longer equipment life, and reduced emissions
What’s the difference between a VFD controller, an AC drive, and a variable speed drive (VSD)?
All these names refer to the same device. VFDs are also known by various other names such as adjustable speed drives, adjustable frequency drives or AFDs, variable frequency drives, variable voltage variable frequency drives, frequency converters, VFD inverters, and power converters.
What is the best way to use a VFD controller?
Variable frequency drive FAQ
What is a VFD and why do I need to adjust motor speed?
A VFD is a type of motor controller that drives an electric motor by varying the frequency and voltage of its electrical power supply. The VFD also has the capacity to control ramp-up and ramp-down of the motor during start or stop, respectively.
Even though the VFD controls the frequency and voltage of power supplied to the motor, we often refer to this as speed control, since the result is an adjustment of motor speed.
There are many reasons why we may want to adjust electric motor speed.
For example, to
- Save energy and improve system efficiency
- Convert power in hybridization or electrification applications
- Match the speed, torque or power of the drive to the process requirements
- Improve the working environment
- Lower noise levels, for example from fans and pumps
- Reduce mechanical stress on machines and motor windings to extend their lifetime
- Shave peak consumption to avoid peak-demand prices and reduce the motor size required
Where should I use variable frequency drives and soft starters?
Today’s variable speed drives integrate networking and diagnostic capabilities to boost control performance and increase productivity. So: reduced energy consumption, intelligent motor control, and reduction of peak-current drawn are three great reasons to choose a VFD as the controller in every motor-driven system.
- VFDs are most commonly used to control fans, pumps and compressors. These applications account for 75% of all drives operating globally
- Conveyors, centrifuges, cranes, lifts and industrial processing equipment which need precise motion control are also common applications for VFDs
- Electric propulsion systems for electric and hybrid ships are another common use where VFDs contribute with essential power conversion in electrification of our future maritime transport system
- Soft starters and across-the-line contactors are other, less sophisticated types of motor controllers. They are used to protect motors on stopping and starting, in simple applications- A soft starter is a solid-state device and provides a gentle ramp-up to full speed during startup of an electric motor
- An across-the-line contactor is a type of motor controller that applies the full line voltage to an electric motor
What is the main advantage of using a VFD?
VFDs trim your power bill.
A variable frequency drive can use VFD control to vary the power supplied to match the energy requirement of the driven equipment, and this is how it saves energy or optimizes energy consumption.
The drive can dramatically reduce energy consumption when compared to direct-on-line (DOL) operation, where the motor runs at full speed regardless of the demand. Using a VFD, speed control does not waste power (unlike regulation with a throttle valve or damper, for example), but instead adjusts the motor power to match exactly the actual demand. Using a variable speed drive, power or fuel savings of 40% are common. The roll-on effect means that the use of drives also reduces NOx emissions and CO2 footprint of the systems in which it is installed.
In which applications do VFDs deliver the greatest electricity savings?
Energy bills are the biggest cost after wages in many industrial companies. You can reduce your energy bill by 20-60% by installing VFDs in the following applications:
- HVAC systems or air transfer in data centers, other buildings, car parks, or tunnels
- Pumps for liquids and water management
- Air compressors
- Other compressors on site, such as cold storage
How much energy can I save using VFDs in fan and pump applications?
By applying variable speed control to fans and pumps, you can typically achieve energy savings of 40%. This is defined by the variable torque curve. For fans and pumps, a 20% reduction in motor speed results in 50% energy savings.
What are the advantages of using VFDs in industrial conveyor and crane applications?
VFDs also play a crucial role in industrial applications such as cranes and conveyors. In these applications, process optimization and precise speed and position control are the primary reasons for using VFDs. For example, the VFD offers integrated condition monitoring and anti-sway functionality. For conveyors, the VFD is equipped with integrated high-precision positioning control as an alternative to servo solutions. VFD-integrated condition monitoring (CBM) with a remote monitoring service works hand-in-hand not only to improve reliability but also to create new benefits in terms of visualization and logging. While VFDs can additionally help to save energy, the savings for conveyors and cranes are unlikely to reach the 40% achieved with fans and pumps.
Are VFDs also relevant for maritime applications?
In marine propulsion, electric motors and VFDs are rapidly replacing diesel engines and mechanical systems. Without VFDs, controlling a ship’s speed and direction would be impossible.
As well as optimizing energy efficiency, VFDs offer a range of other benefits in marine applications. The advantages include integrated functional safety, easy integration into ship systems, compact control in limited spaces below deck, and improvement of power quality on board.
Many ships still use diesel generators to make electricity. However, fully electric ferries are quickly becoming more common.
What is the fastest way to decarbonize your business?
Did you know that 26% of existing installed AC motors are fitted with VFDs? And 75% of these motors drive variable torque loads (fans, pumps and compressors). Control of variable torque loads has the potential to save the most energy, in an industrial plant. Investing in variable frequency drive (VFD) technology to control these applications, along with potential utility rebates, is one of the fastest ways to reduce your energy bills and decarbonize your plant.
How can you eliminate valve or damper control, and reduce your motor size too?
Did you know that 95% of electric motors are oversized or sized for the peak-load scenario? Many existing systems still operate with mechanical constriction (valves or dampers) to adapt the oversizing for partial loading. VFDs can replace the valve control to save a surprising amount on running costs for motor or driven load. And this allows you to reduce the dimensioning of your electric motor at the same time.
What payback time can I expect when investing in VFDs?
When investing in VFDs, the typical return on investment is as short as 6-12 months.
Example: A 7.5 kW pump running 8,000 hrs annually consumes electricity costing $6,000 per year, based on electricity charge of 10 cents per kWh.
- Installing a VFD to reduce motor speed by just 5Hz (10%) delivers 27% savings in electricity consumption: $1,600 savings per annum
- Total savings during lifespan: $40,500
- Payback time: 6-12 months