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A variable frequency drive (VFD) is a device used to control the speed of an electric motor in order to:

• Enhance process control
• Reduce energy usage
• Decrease mechanical stress on motor control applications, to protect equipment
• Optimize the performance of applications that rely on electric motors
• Control ramp-up and ramp-down when a motor is either starting up or stopping.

What is a VFD?

Your operation runs on a complex system that consists of many dynamic parts, meaning it requires a great level of control to operate smoothly: whether that comes in the form of motion control, motor speed control, servo motion control or otherwise. And so, the right variable frequency drives (VFDs), bring greater intelligence and efficiency to your operations for an overall better performance. Using VFDs, you can maximize system uptime, extend motor lifetime, and reduce energy consumption by up to 80%.

Learn more about VFDs

• VFDs compatible with all motor types
• Low-harmonic drives
• Intelligent drives
• Low-voltage single- and three-phase drives
• Medium-voltage drives
• Decentral drives

Explore the world’s broadest portfolio of variable frequency drives 

Reduce energy consumption by up to 80%. By working with different voltages and frequencies, variable speed drives can control the speed of electric motors to align with load demand – instead of running at full speed at all times. By matching motor speed precisely to demand, it’s possible to enhance process control, reduce energy usage and optimize the performance of motor control applications.

Today you can find a wide range of VFDs, with single-phase and three-phase varieties in particular having evolved to suit a number of applications. Drives also differ when it comes to the methods used to control frequency and voltage, with some relying on harmonic mitigation technology to function. Explore the range

Increasingly, energy storage is being used to create hybrid solutions such as DC/DC converters, which help improve performance by optimizing energy. Although there are various energy storage methods available, decreasing battery costs and increasing energy density have made battery utilization the fastest growing and most easily integrated storage medium available today. With a DC/DC converter you can connect to a wealth of sources including batteries, super capacitors, fuel cells, solar panels and the like.

Where can you get help anytime, anywhere, to troubleshoot your Danfoss drive or power converter? When you need information quickly, ask MyDrive® Assistant for fast, AI-guided troubleshooting. Ask MyDrive® Assistant

Visit the Drives expert hub to browse a wealth of information about all the ways in which VFDs and power converters can optimize your operations. Here you can read more about cybersecurity, energy efficiency, condition monitoring. harmonic mitigation, and more.
Or, explore our many case stories to learn about real-life installations equipped with VFDs and power converters.

A VFD is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. It also has the capacity to control the ramp-up and ramp-down of the motor during start and stop, respectively.

A soft starter is a solid-state device and type of motor controller that only provides a gentle ramp-up to full speed during the 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.

Power is the rate of doing work, which is the amount of energy transferred in a given timeframe. Because the energy requirement for the driven equipment (pump, fan, compressor or any other mechanical movement) in a motor-drive system (MDS) typically varies over the operating period, supplying more than the power needed will result in wasted energy or inefficient use of energy. A VFD has the ability 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 ability of a VFD to gradually ramp the motor up to speed will reduce peak current drawn during startup, which delivers two main benefits to users:

1. Protection from peak-demand electricity prices that the utility charges to companies for exceeding preset limits

2. Protection of the motor equipment against premature damage due to exceedingly high peak currents exposure during startup

In addition, today’s VFDs integrate networking and diagnostic capabilities to better control performance and increase productivity. So, energy savings, intelligent motor control and reduction of peak-current drawn are three great reasons to choose an variable frequency drive as the controller in every MDS.

Installing a VFD as a motor controller in an motor-drive system can often increase the system efficiency by up to 30%. The average payback period varies but rarely exceeds 3 to 4 years, making such an investment a highly cost-effective measure with a good return on investment (ROI).

The PWM technique requires switching the VFD's inverter power devices – transistors or insulated-gate bipolar transistors (IGBTs) – on and off many times in order to generate the proper root-mean-square (RMS) voltage levels. Controlling and varying the width of the pulses is how PWM varies the output frequency and voltage.

The three major variable frequency designs used today are PWM, current source inverter and voltage source inverter. The PWM technique is the most common.

Generally, for industrial facilities, the measured value of total harmonic distortion at any point of common coupling (PCC) should not exceed 5%. Based on this, the recommended correction methods are an active front-end drive, a low harmonic VFD with an active filter and an 18-pulse drive. Learn more about harmonics and efficient harmonic mitigation