Support
42 frequency are applied to the motor and the motor speed is solely dependent on the number of motor stator poles .
In comparison , a VSD delivers a varying voltage and frequency to the motor , which then in turn determines the motor ’ s speed . The higher the frequency supplied to the motor , the faster it will run . Power applied to the motor through the VSD can therefore have the motor working speed lower than the nameplate base speed or increase the speed . This is set up to match the equipment requirements .
VSDs come in different sizes ranging from 0.18kW through to Mega Watts and are available as stand-alone devices , as part of supplied control systems or integrated into a motor .
A VSD can be used for simple applications , such as controlling a pump or a fan where variable air flow is required . They can be interfaced with a transducer , such as a pressure sensor , and programmed to operate within specific parameters . VSDs are used in a wide variety of systems including most kinds of ventilation systems , air extraction systems , cooling systems , unitary air conditioning systems , water pumps and central air conditioning systems to name a few . Unitary ‘ Inverter systems ’ are now widely used and offer considerable energy savings .
VSD VERSUS SOFT STARTERS VSDs offer all the benefits of a soft starter but add much more flexibility in terms of features and settings and in most applications , bigger energy cost savings . Not only do VSDs provide an extremely smooth and controlled start , but they also efficiently control motors to nearly any desired level of speed , torque , or position , including over-speed and full torque from start .
As I said before , in most applications VSDs , controlling speed and torque to demand greatly improves efficiency and yields considerable energy savings .
The biggest advantage of a soft starter over a VSD is the lower initial cost . If matching of the speed of the process is not required , then the initial cost of the product tends to become a bigger factor , which might make a soft starter a more optimal choice . If the system can be optimised or additional costs can be saved on electricity and / or by reducing maintenance costs of the overall system then a VSD may be the optimal choice .
ENERGY CONSERVATION UTILISING VSDS IN HERVAC SYSTEMS Among the advantages of using a VSD , the biggest is the energy usage reduction and the consequent cost savings . Energy savings of between 25 and 70 % can be realised on a three phase motor . VSDs are , at the moment , possibly the most effective method for controlling motor speed in response to varying system operating requirements . Since motors consume energy , the importance of motor control matching load demand increases as energy supply becomes more expensive and our supply more and more strained .
RACA Journal I March 2023
A small decrease in the speed of a pump or fans can result in large decreases in energy usage .
VSDs are ideal for equipment with varying load conditions such as HVAC systems and even in the most energy-efficient HVAC systems , VSDs will help to further reduce energy usage .
The following points give an idea as to possible usage :
• There exists a broad range of VSDs available specifically for heating , refrigeration , ventilation and air conditioning applications . Many of these drives can be integrated into a building management system to improve flexibility and optimise energy efficiency .
• The effect of the addition of VSDs results in that when a system requires less cooling or heating than the maximum load , VSDs allow compressors , fans or pumps to operate at lower speed and as a consequence , use less energy .
• In ventilation systems for large buildings , VSDs on fans save energy by allowing the volume of air moved to match the system ’ s demand .
• VSDs can vary the output of your HVAC system to meet an installation ’ s actual requirements , again offering decreased load on the energy supply and increased energy savings .
• VSDs are one of the most cost-effective methods to increase efficiency and reduce the costs of HVAC systems – they cut power usage and prevent energy wastage by precisely matching motor speed with cooling and circulatory demand .
• When looking at the bigger picture we find that by virtue of their energy intensiveness , heating , ventilation and air conditioning systems account for a large percentage of buildings ’ energy costs .
• HVAC systems are responsible for 26 % of the electricity consumed in the commercial sector , with motors that drive compressors , pumps and fans in these systems accounting for more than 98 % of that energy .
• VSDs are potentially the most under-utilised tools for optimising the energy efficiency of electrical equipment . Using them in suitable applications such as HVAC systems can save energy , cut operating costs and extend the lifespan of equipment .
" VSDs are used in a wide variety of systems including most kinds of ventilation systems , air extraction systems , cooling systems , unitary air conditioning systems , water pumps and central air conditioning systems to name a few ."
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