|Motor & Drives
Motors are used to run HVAC systems,
elevators and other equipment, and can account for up to
50 percent of your facility's overall energy use. Over a
typical 10-year operating life, a motor can consume electricity
valued at 50 times the original cost of the equipment. Using
this calculation, a $1,000 motor running continuously for
a decade could cost you up to $50,000 in electricity.
Energy-efficient motors are
good investments. Even if they yield only 2 to 8 percent
in energy savings, these motors generally achieve incremental
paybacks in 2.5 to 5.0 years compared with buying less-efficient
Adjustable-speed drives (ASDs)
- sometimes referred to as variable-speed
drives (VSDs) and variable-frequency
drives (VFDs) - regulate motor speeds according
to the amount of work required. Reducing motor speed
by 10 percent can cut power consumption by 27 percent,
and a 20 percent speed reduction can cut consumption
by 49 percent. These drives are particularly useful
when combined with high-efficiency motors since they
tend to run faster than conventional motors. An added
benefit is their ability to reduce noise - an important
consideration near guest rooms and small meeting rooms.
These drives can save on your facility's total energy
consumption, but tend to be expensive, with approximate
paybacks between two and eight years.
The Vocabulary of Motors
Motors are classified as AC (alternating current from outlets),
DC (direct current, usually from a battery) or universal
(operating as either AC or DC). A motor's mechanical power
is measured in either kilowatts or horsepower (1 hp = 0.746
kW). The two factors that determine power are torque (measured
in newton metres or pound feet) and speed (measured in revolutions
per minute [rpm]). The slower a motor operates, the more
torque it must produce to deliver the same amount of power.
A motor's efficiency is a measure of the energy it delivers
(output) relative to the energy it uses (input).
Power-factor correction capacitors
are devices that store electrical charges and
reduce the consumption of reactive power that motors
need to generate magnetic fields. These are important
only if you have demand charges on your electricity
Energy-efficient drive belts have
teeth or longitudinal grooves that improve grip, reduce
slippage and are only slightly more expensive than standard
V-belts. Ensure that drive-belt inspections are performed
every few months as part of regular maintenance, and
replace the belts when they wear out.
Choose the right motor for
the job. Oversizing is the inefficient practice
of employing a larger motor than required for a task.
This is a particular concern if the motor is loaded
under 50 percen