Page 39 - Energize November 2022

TECHNICAL

Benefits of variable speed drives

in industrial applications

Information from ABB

What is a variable speed drive? usually makes the start-up process very labour intensive as
The basic function of a variable speed drive (VSD) is to control starting a pumping station, for instance, could take one person
the flow of energy from the mains to the process. Variable up to an hour. The labour costs add up with personnel having
speed drives sit between the electrical supply and the motor. to sometimes travel long distances to remote sites. In some
Power from the electrical supply goes into a drive and the facilities this process is automated, but consumption of energy
drive then regulates the power that is fed to the motor. is poor.
Inside the drive the input power is run through a rectifier
that converts the incoming AC power to DC power. The DC There is a more energy efficient alternative
power is fed into the capacitors inside the drive. This is done Running these applications with variable speed drives results
to smooth out the electrical waveform which provides the in instant savings in energy consumption while it also brings
clean power supply for the next step. Power then flows from long-term competitive advantages. Any process that is using
the capacitors to the inverter, that changes the DC power to electric motors can get important monetary savings and
the output AC power which goes to the motor. operational benefits with the use of variable speed drives. You
This step allows the drive to adjust the frequency and the might want to take a good look around your own operations
voltage that fed into the motor based on your current process and processes, no matter how big or small, to see where
demands. This means you run your AC motors at the speed targeted use of variable speed drives can help you get fast
or the torque needed. This is why using the AC drives is very financial payback and long-term competitive advantages.
cost-effective.
Besides saving energy, variable speed drives also help How do variable speed drives regulate power to
you reduce maintenance costs, waste and even ambient match the motor’s speed to what is required by
noise emissions. They are also a great way to help meet your the process?
environmental goals. Figures 1 to 4 below describe the process graphically.

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% 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 key to helping you reduce your energy use and
CO 2 emissions, or even finding 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 Figure 1: Convert incoming AC to DC: Incoming 3-phase AC power is fed
by manual opening and closing of valves in the pipelines. This into a rectifier that converts it to DC power.

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