Variable frequency drive, also known as variable speed drive (VSD), is a technology that is used to control the speed of machinery. Many industries operate machines at different speeds while making different products. Where conditions dictate there should be an adjustment to the flow from a fan, adjustable speed drive technology helps to save energy while performing the task perfectly. Variable frequency drive has been used in compressors to control the RPM of the system. This sin turn helps to save energy and offers better performance than a fixed speed equivalent.
How VSD works to save energy
For many years, the key applications for a Variable frequency drive
system have been a fan system and a pump. Technological advancement has led to the inclusion of other applications such as compressors, which proved to offer better results and reliability.
A variable frequency drive controlled compressor works with the help of an AC to control the speed of the compressor system. VSDs reduce the energy consumption of a compressor by ensuring the motor runs at a higher than normal speed and delivers higher torque.
The variable frequency drive system controls the waveform of the voltage and current leading to the motor. It also helps to convert incoming AC power to DC then later to quasi-sinusoidal AC. This ensures the output power is sufficient to cater for the deficiency in the system and to optimize performance. Apart from reducing power costs, variable frequency drive also reduces power surges and ensures constant pressure is maintained for efficiency.
Verified VSD Controlled Compressors
Despite the fact variable frequency drive compressors are new applications, several installations have proved successful after testing. A case in Belgium highlights the stepping up of 275kW fixed speed compressor to 315kW VSD compressor. During testing of the system, it was concluded that it could save as much as 18 to 25 percent energy, which translates to more than €15,200 annually.
Similarly, in a European biochemical firm, it was discovered the power consumption while using the old system was high, so they supplied the system with VSD, an attempt that resulted to savings of 1,700,000 kWh annually. The installation of the VSD also led to reduction in CO2 released by up to 850000 kilograms on annual basis.
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