Variable Speed Drives (VSDs)
Easy Energy Savings with
WEG IE3 motor and VSD
T
he implementation of energy efficient solutions
across the agricultural sector is enjoying greater
focus as both larger commercial operations
and smaller farmers continue the move to decrease
electrical consumption and reduce overall costs.
Focus is being placed on those
applications that consume lots of
energy, one of which is irrigation.
This is according to Machiel de
Bruyn, drives and automation sales
engineer at the Zest WEG Group,
who says that contrary to what
some may believe it is quite easy
to lower the energy consumption of
an irrigation system by applying the
latest available technology.
“Energy savings can be achieved
easily and quickly by installing
high efficiency motors which are
engineered to reduce energy
consumption,” de Bruyn says. “It
is important to understand that
between 80 and 90% of the total
cost of ownership of an electric
motor is attributed to electricity
costs, and with consumption at
this level, any increase in efficiency
would immediately make a
tangible difference.”
Developed
for African market
Significantly, WEG developed its
IE3 electric motors for the African
market and in a bold initiative
Zest WEG Group Africa was the
first equipment supplier to move
from IE2 motors to IE3 compliant
motors, and a key aspect was that
that change was introduced at no
additional cost to its customers,
thereby reducing the total cost
of ownership. De Bruyn says that
changing out the motor to a WEG
IE3 will result in a quick win.
The WEG IE3 electric motors
have been designed and built
for the often harsh operating
environment found on the
continent and they boast features
that would not be found on
similar products in European
markets. This is important as it
Power Saving Calculations (R0.69 = 1kWh)
Squared Torque
P=2nT PN3 PΝ2
Power is proportional to the cube or the speed.
i.e 80% speed = 51% power or 50% speed = 12.5% power
Normal Power Throttling = 87% power @ 80% Flow
Example: 250kW installed, 51% power absorbed @ 80% speed and 80% duty cycle.
Normal annual power = 1609 MWhr at a cost of R1 110 210.00
Customer information capture at events/reception
and Customer satisfaction surveys
VSD annual power = 921 MWhr at a cost of R635 490.00
First year saving = R474 720.00
A power saving calculation typical to centrifugal pumps.
means the motors are considered
fit-for-purpose- and are capable
of meeting performance and
reliability expectations.
The ingress protection has been
increased to IP66, a patented
W3 shaft seal has been included,
insulation has been upped to Class
H and the motors are 100%variable
speed drive (VSD) compatible.
De Bruyn explains that coupling
the motor to a VSD offers further
energy efficiency benefits.
Further benefits
It is often necessary in a motor and
centrifugal pump combination
to run the motor at
reduced speeds. If
the motor runs at
80 % of its
nominal speed to get to a required
flow and pressure, and when this
happens only 51 % of the power
is actually being used. By coupling
the motor with a VSD, the end-user
will be able to lower the speed of
the motor to achieve the pressure
required in the installation and will
therefore only incur the cost of the
energy consumed while operating
at this lower speed.
This is particularly useful where an
operation alternates between pivot
and micro irrigation. Generally the
micro irrigation system will require
a much lower pressure and in
many cases the valve leading to the
micro irrigation system would be
“choked” or “throttled”. Essentially
this means that the motor will still
be running at 100% speed, but will
only deliver half of the required
flow rate and pressure.
By operating an irrigation system
like this, the operation will be
paying the energy cost in full,
but only receiving a reduced
delivery in return.
The WEG motor/VSD combination is an energy efficient solution.
As an added advantage
and
proof
of
its
commitment to sustainable
relationships
with
customers, Zest WEG Group
has extended the guarantees
on all WEG products, with
those on WEG motors being
five years and on WEG VSD and
softstarters two years.
SABI | AUGUST/SEPTEMBER 2016
39