SABI Magazine August September 2016 V 7 | Page 41

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=2nT PN3  PΝ2 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