Why Use a Drive with
Your Compressor?

  2 minutes read

Give your customers capacity control, greater efficiency, and more by adding a dedicated drive to your system design.

As a designer of cooling and refrigeration systems, you’ll know that not every compressor needs a drive. The smallest compressors – those found in domestic refrigerators, for example – manage perfectly well by just switching on when cooling is needed and off again when it’s not. At the other end of the spectrum are highly specialized installations, where system architecture is driven by other priorities.

Yet between these two extremes lies a substantial category of industrial and commercial cooling applications where adding a drive can create real value. Whether you’re designing a chiller system, an air handling unit, a rooftop system, or commercial refrigeration equipment, a drive can give your compressor something it wouldn’t have otherwise: the ability to adapt continuously to changing operating conditions instead of either running at full speed or not at all.

Adapting Capacity
to Demand

The main job of a compressor drive is to enable your compressor to adapt to changing demand. In cooling applications, cooling demand is rarely constant, as occupancy, weather conditions, and process loads are always in flux. Without a drive, compressors can really only respond to these fluctuations by repeatedly starting and stopping.

A variable-speed drive offers a better option. Instead of simply switching on and off, a compressor governed by a drive adapts its speed continuously to deliver the capacity your system requires at any given time. This helps your solutions stand out in the market, thanks to smoother operation, more stable pressure and temperature conditions, and less start-stop cycling.

Incorporating a drive also gives you greater flexibility when designing systems that have to perform efficiently across a wider operating range. In some applications, a drive can even allow the compressor to operate beyond its nominal rating when operating conditions permit.

Meaningful Efficiency Gains

If a drive enables your compressor to follow incremental cooling demand, the compressor spends more time operating at an appropriate working point – instead of constantly cycling between maximum output and zero. In other words, the variable-speed operation a drive enables can improve part-load efficiency compared to repeated on/off operation – and can thus significantly improve overall system efficiency.

Another advantage to incorporating a drive in your design is that it enables you to use high-efficiency permanent magnet motors, which require electronic drive control to operate. For any OEM looking to reduce energy consumption without redesigning an entire system, adding a drive can contribute in more than one way.

Benefits Beyond Efficiency

While capacity control and the efficiency this enables are usually the main reasons for choosing a compressor drive, they aren’t the only ones. A drive makes sure your compressor starts in a controlled manner, reducing the high inrush currents associated with direct-on-line starting. This can reduce electrical stress on the installation while also lowering mechanical stress on the compressor itself.

Many compressor drives also include dedicated functions that support lubrication during startup and low-speed operation, helping the compressor remain within its intended operating range.

Yet another benefit involves diagnostics. A drive has access to a wealth of information about your compressor and its operating conditions. It knows the motor speed, load, current, operating hours and fault history, and can generate warnings and alarms long before a technician reaches for a toolbox. For commissioning engineers and service technicians, this information can make fault finding considerably faster.

The Dedicated Advantage

While your compressor can be controlled by a general-purpose “bookshelf” drive, the dedicated drives that OJ specializes in are designed specifically for compressor applications – and this approach yields serious benefits.

Mounted close to the compressor itself, a dedicated drive can eliminate the need for a separate cabinet and long cabling to the motor. These “lean and mean” drives provide all the functionality you need for your compressor applications, but nothing you don’t need – enabling a very compact solution that’s easy to integrate into your system. All of this simplifies manufacturing, installation and servicing, especially for prefabricated units – enabling you to bring your systems to the market faster and more affordably.

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Lasse Larsen, Product Manager Drives

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