When it comes to industrial compressed air systems, there are generally two operational drive types:
In a fixed (or constant) speed compressed air system, the motor runs at the same RPM regardless of application or product air demand. The inlet valve opens and closes to maintain pressure within the internal compressor systems. As a specific application consumes air, pressure falls and the system requires more air volume as replenishment, the valve will open. Meanwhile, if there is no load applied to the compressor and the air must remain at a constant pressure, the valve will close.
Fixed-speed drive machines are more common in many industries, and as such, operators usually enjoy high accessibility to a large number of parts they may need. Further, maintenance and repair costs are often low due to the greater availability of compatible parts.
Fixed-speed drive machines tend to come with lower initial price tags than their VSD counterparts. However, since neither the voltage nor the electric frequency (Hz) supplied to the motor at any given time varies, fixed-speed drive compressors experience lower energy efficiency overall since the motor is rarely using the power it receives to its fullest potential. Though fixed-speed drive air compressors may offer a lower initial investment, they tend to cost considerably more money over time due to the higher energy costs associated with using the machine at less than full-rated capacity.
On the other hand, an air compressor with a variable frequency drive features a motor that modifies its speed in accordance with application needs. It does so by modulating both the voltage and the Hz supplied to the motor. Ideal for applications that vary from 40 to 75% of full-rated capacity, this kind of compressor is capable of operating across a full range of capacities up to 100% of rated airflow. In applications where the average air demand approaches 100% capacity, a fixed-speed compressor is the best choice, as a VSD compressor will consume more energy at 100% capacity. Further, while a VSD compressor tends to spend a lot of time producing air, it can also go off-load or be completely turned off during periods of extremely low or no demand.
As a result, VSD compressors experience much higher rates of energy efficiency over time. In fact, installing a variable-speed drive machine can save up to 70% of energy consumption in a typical facility. By mitigating wasteful part-load energy consumption, variable speed drive compressors optimize your facility’s airflow — and can usually pay for themselves within three years.
Besides lower energy consumption and higher savings, variable-speed drive compressors come with a number of operational benefits. A compressor operating at higher efficiency generates higher production levels with less wasted product — and thus increased ROI and maximized profitability. With properly sized air receiver tanks, VSD compressors can better ensure consistent plant pressure, enjoy longer component service lives thanks to less wear, and operate at lower decibels than a fixed-drive. What’s more, employing a VSD compressor may qualify you for energy incentives from a slew of industry organizations and private companies.
According to the experts at Fluid Air Dynamics, a variable-speed drive compressor is ideal for meeting the needs of any air supply that has variability in demand — “from single shift seasonal type businesses that have higher levels of production for three months out of the year to a 24/7 shift operation in which shifts 2 and 3 have different levels of air demand than shift 1.”
Regardless of your compressed air needs, it should be clear: while fixed-speed drive compressors provide lower initial investment solutions for end users whose airflow demands remain constant, most applications have great variability in air demand. As the “big money” is in the cost of operation, a variable-speed drive compressor is usually the best choice for boosting energy efficiency and profitability by letting your company pocket the savings (instead of the power company).
Variable-speed drive compressed air systems, like the Mattei OPTIMA series, utilize state-of-the-art “bearingless” rotary vane airend technology that, unlike screw-based models, never experience efficiency drop-offs — thanks to better volumetric compression design and the lack of bearings to wear. With lower operating costs at comparable flow rates, rotary vane VSDs provide even higher energy savings for your business. Invest in a Mattei VSD compressed air system to capitalize on our 90% mechanically-efficient air production and longer service lives than any other rotary system on the market.