Variable Speed Drives

The basic function of a variable speed drive (VSD) is to control the flow of energy from the mains to the process. Variable speed drives sit between the electrical supply and the motor. Power from the electrical supply goes into a drive and the drive then regulates the power that is fed to the motor.

Inside the drive the input power is run through a rectifier, that converts the incoming AC power to DC power. The DC power is fed into the capacitors inside the drive. This is done to smooth out the electrical waveform which provides the clean power supply for the next step. Power then flows from the capacitors to the inverter, that changes the DC power to the output AC power that goes to the motor.

This step allows the drive to adjust the frequency and the voltage that fed into to the motor based on your current process demands. This means you run your AC motors at the speed or with the torque according to the demand needed. This is why you can save large amounts of money using the AC drives.

Besides saving energy, variable speed drives also help you reduce maintenance costs, waste and even ambient noise emissions. They are also a great way to help meet your environmental goals.

What is the difference between a variable speed drive, a variable frequency drive and an AC drive?

Variable speed drives (VSD) are sometimes called Variable Frequency Drives (VFD) or AC drives.

Using variable speed drives to control motors can lead to big savings

Nearly 70 percent of all industrial electrical energy use goes to powering electric motors. These motors are the workhorses of business, from pumps moving fluids to fans moving air to compressors, conveyors, and every type of machine that depends on rotational force to get its job done.

And it’s these motors that are the key to help you reduce your energy use and CO2 emissions, or even find more energy efficient solutions for your customers. Pumps, fans and compressors are often run at constant speed, with control of flow rate and destination being done by manual opening and closing of valves in the pipelines. This usually makes the startup process very labor intensive as starting a pumping station, for instance, could take one person up to an hour. The labor costs add up with personnel having to sometimes travel long distances to remote sites. In some facilities this process is automated but consumption of energy is poor.

There is a more energy efficient alternative. Running these applications with variable speed drives results in instant savings in energy consumption while it also brings long-term competitive advantages. Any process that is using electric motors can get important monetary savings and operational benefits with the use of variable speed drives. You might want to take a good look around your own operations and processes, no matter how big or small, to see where targeted use of variable speed drives can help you get fast financial payback and long-term competitive advantages.

How can you benefit from variable speed drives?

You can get savings in...

  1. Energy
  2. Operational costs
  3. Downtime
  4. Maintenance
  5. Raw materials 


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