INFORMATION SHEET
MINNESOTA
Technical Summary: Variable Frequency Drives
60%
Flow rate
50%
40%
Torque
(pressure)
30%
20%
Output
power
100%
90%
80%
10%
70%
• VFDs operate on an as-needed basis, saving energy, money
and maintenance costs
70%
60%
• Added control—smoother acceleration and deceleration,
automated response to system conditions (e.g. pressure,
flow, etc.)
80%
50%
Benefits of VFDs
90%
40%
• A reduction in frequency results in the shaft of the motor
spinning at speeds lower than the standard 1200, 1800,
and 3600 RPMs (depending on the motor)
100%
30%
• A VFD changes the frequency and voltage supplied to
the motor
•Example:
– Flow increase 10%
– Power increase 33%
– Small decrease in flow = bigger decrease in power
20%
Fundamentals of VFDs
• Centrifugal fans and pumps offer the highest potential
for savings
10%
Variable frequency drives (VFDs), also called adjustable speed
drives (ASDs), allow induction-motor-driven loads such as fans
and pumps to operate at increased efficiency. By controlling motor
speed so that it finely corresponds to varying load requirements,
VFD installations can increase energy efficiency and process
precision, and afford other performance benefits such as over
speed capability. They can also eliminate the need for expensive
and energy-wasting throttling mechanisms such as control valves
and outlet dampers.1
Energy savings potential
Flow, torque or output power
What is a variable frequency drive
or adjustable speed drive?
Speed, percentage of revolutions per minute
• Energy savings—especially on variable-torque centrifugal
fan and pump applications
• Savings vary by application
• Improved process control, such as speeding up or slowing
down a machine or process
• Applications such as extruders and conveyors may experience
savings, but not to the same degree as fans and pumps.2
• Bypass capability in the event of an emergency
• Protection from overload currents
• Extending the life of your motor equipment
• Reduce noise
www.esource.com
Extruders and conveyors are Custom VFD applications
1
2
Market segments
• Industrial processes, such
as glass manufacturing,
mining, refining
• Commercial real estate
•Churches
• Food processing
• Grocery stores
• Commercial space
(retail and real estate)
•Hotels/motels
• Schools and universities
• Cold storage
•Hospitals
INFORMATION SHEET
TECHNICAL SUMMARY: VARIABLE FREQUENCY DRIVES
MINNESOTA
VFD Case Study: Greater Twin Cities United Way
VFD UPGRADES YIELD BIG RETURN ON A SMALL INVESTMENT
PROJECT SNAPSHOT
Project
Installing two 15 hp
VFDs
Total Energy
Savings
32,665 kWh
Xcel Energy
Rebates
$2,500
Payback
Less than 17
months
Projected Annual
Savings
Additional
benefits
$3,200
More control over
system
The situation:
We are here to help.
• A resourceful nonprofit with a 68,000 sq. ft. facility in the heart of downtown
Minneapolis was looking for ways to maximize their operating budget.
For assistance in determining if VFDs
would benefit your facility, or to find
out more about rebates, contact one
of our dedicated energy efficiency
specialists in our Business Solutions
Center at 1-855-839-8862 or
[email protected].
Or visit our website at:
xcelenergy.com/MotorEfficiency.
• In need of energy efficiency upgrades, they started with the low-hanging fruit—
projects such as lighting.
• In order to maximize the energy savings potential, they also replaced their air
conditioner and air handler (both of which were installed in the 1960s).
Their engineers suggested installing variable frequency drives (VFDs) on the wall fans
of the newly installed air handler to maximize their energy savings. VFDs are used in
commercial and industrial settings where the climate of a large space needs to be
controlled. And with 68,000 sq. ft. of space, you could say the Greater Twin Cities United
Way qualified.
As you can see from the project snapshot above, a not-so-obvious, small, energy
efficiency upgrade can be a big bonus. And you don’t have to be a nonprofit to get on
board with that. To see the full case study on the Greater Twin Cities United Way or
other similar customer case studies visit ResponsibleByNature.com/Case-Studies.
Be aware that VFDs are not beneficial for every application and some are not eligible for
a rebate.
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of Xcel Energy Inc. | Northern States Power Company-Minnesota, an Xcel Energy
Company. | 15-09-532 | 09/15