Variable Frequency Drives (VFDs), also known as Variable Speed Drives (VSDs), have been the norm for adjusting the speed of induction or synchronous motor since the late 1980s. VFDs are used to regulate the engine speed in a variety of applications, including fans and machines, but industrial pumps are one area where they are especially advantageous. Learn more about this at https://www.ablesales.com.au/power-equipment/diesel-electric-pressure-washers/
In this article, we discuss the benefits of utilising a variable frequency drive (VFD) to adjust pump speed as opposed to the valves that have historically been used to control the flow from the pump.
Life cycle cost (LCC)
LCC analysis is a technique for estimating a system's total life-cycle cost. This comprises the expense of the system's implementation and maintenance as well as the expense of the fuel used to operate efficiently, the cost of operating and maintaining the system, and the price of dismantling and disposing of the system.
Many businesses only examine the price of buying and installing a system once. Plant designers and managers should examine the Life Cycle Cost (https://www.patriotsoftware.com/blog/accounting/life-cycle-costing-process/) of several options before implementing substantial new equipment or undertaking a major renovation. This assessment will help you find the most cost-effective options.
Organizations must always look for ways to reduce their costs in order to increase the sustainability of their operations in light of the increasing competition in national and worldwide marketplaces.
As a source of efficiency gains, plant equipment operations are gaining special consideration, particularly in the area of reducing energy usage and downtime. Aside from cost savings, many firms are concerned about the environmental effect of their operations and are investigating fuel efficiency as a means of reducing emissions and conserving natural resources.
Speed control
Speed control is the most apparent reason to buy a variable frequency drive. For operational, budgetary, and procedural reasons, this is often done. When a variable frequency drive is used, maintenance costs are reduced since the DC motor carbon brushes and mechanical speed control gears are eliminated (transmissions). In the case of pumps and fans, variable frequency drives provide the most evident cost advantages. Pump and fan power consumption is inversely related to velocity cube. If a fan can be operated at 80 percent of maximum speed, it potentially consumes 51% of full load electricity.
Improved characteristics of motors
The characteristics of motors may also be improved using variable frequency drives. Motors may be brought to full speed in a fraction of the time using variable frequency drives, which take just 100 to 150 percent of the maximum load current (FLAs). The ability to start at normal FLA is critical, if the power source cannot handle the standard six times FLA across-the-line starting draw or even the 350 per cent FLA soft-start device current. The magnetic flux of an induction motor is controlled using variable frequency drives. Voltage is directly proportional to magnetic flux, but the frequency is inversely proportional. The inrush current does not surpass the motor's FLA rating if the flux remains constant. This is a substantial improvement over a soft-start, which suffers from excessive voltage drop issues and is unable to start at full power.
Energy saving
In a book titled "Variable Speed Pumping: A Guide to Successful Applications," seven different strategies for reducing one's energy consumption are presented.
1. Conceive systems that demand less capacity and total head than existing ones. Do not make the assumption that these standards are set in stone.
2. You shouldn't give yourself a large leeway when it comes to the capacity and/or the total head. If the demands continue to grow, it is likely going to be more cost-effective to expand pumping capacity later on.
3. Despite the inclination to place a greater focus on the initial cost, you will end up saving money in the long term if you choose the pump type and size that is the most efficient from the beginning.
4. Use variable speed drives (VSDs) to reduce losses caused by throttle valves and bypass lines, with the exception of situations in which the system is intended to have high static heads.
5. Instead of using a single bigger pump, use two or more smaller pumps so that any surplus pump capacity may be shut off.
6. To prevent the loss of pressure-based energy that would otherwise be lost, use pumps that can also function as turbines.
7. To prevent a reduction in the system's overall efficiency, pumps and all other components should be kept in almost new condition at all times.
Other benefits of VFD's
By replacing the motor starting on a centrifugal pump with a suitable VFD, the high and low limit float switches may be removed from the tank and replaced with a level sensor transducer system. If the analogue output of this transducer is inversely proportional to the water level in the tank, the VFD may receive this signal and change the speed of the motor (and hence the flow from the pump) smoothly and variably under the majority of process situations using PID control (https://www.omega.com/en-us/resources/pid-controller-application-examples).
Importantly, this will avoid repeated short-term overloading of the electrical supply every time the pump begins, as well as mechanical shocks such as water hammers, which may cause damage to pipes, joints, and seals, and can significantly decrease energy usage.
VFDs help minimise the maintenance expenses of a pumping system, which is another significant factor in the overall lifespan cost of a pump. In addition to large energy savings, one of the primary advantages of utilising a VFD to regulate the pump is its inherent gentle starting and stopping, which reduces the likelihood that pipes and valves would be damaged by a sudden change inflow.
Conclusion
Pump users have a huge potential to cut energy costs, increase performance, and prolong the life of their equipment when they combine the power of submersible pumps with the efficiency of variable frequency drives (VFDs). Variable frequency drives would not be as extensively utilised and accepted as they are now if they did not provide substantial economic advantages.
