Inverter compressor

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In air conditioning, an inverter compressor is a compressor that is operated with an inverter.

Contents

In the hermetic type, it can either be a scroll or reciprocating compressor. This type of compressor uses a drive to control the compressor motor speed to modulate cooling capacity. Capacity modulation is a way to match cooling capacity to cooling demand to application requirements.

The first inverter air conditioners were released in 1980–1981. [1] [2]

Market needs for variable capacity

Typical load profile in a building HVAC operating at full load.png
Typical load profile in a building

Many refrigeration and air conditioning systems require reliable processes; The cooling requirements vary over a wide range during the day and over the year due to ambient conditions, occupancy and use, lighting, etc.

Working principle

A variable-frequency drive controls the speed of the compressor motor. The compressor is specifically designed to run at different motor speeds to modulate cooling output. Variable speed operation requires an appropriate compressor lubrication system. Proper oil management is a critical requirement to ensure compressor reliability. The oil management system provides proper lubrication for the Scroll compressor at low speed and prevents excess oil from being injected into the circuit when operating at full speed.

Applications

Variable speed technology can be implemented in HVAC, close control and process cooling applications and as diverse as packaged or split air-conditioning units, rooftops, chillers, precision cooling, VRF and condensing units.

Rooftop
This is a very common unit type. The rising cost of energy means that air conditioning manufacturers must develop a new generation of high-efficiency, cost-effective air conditioners for commercial buildings that meet or exceed a part-load efficiency standard of typically 18 IEER. The aim is to reduce energy use by 30% over current equipment. Inverter technology helps OEMs to build units which meet this demand.
Air handling units
These have integrated cooling and are used in commercial applications for air conditioning and humidity control in diverse ranges of buildings such as small office buildings, fitness and medical centres. Inverter compressor solutions enable smooth modulation and huge energy savings.
Modular chillers
A typical modular chiller installation uses multiple fixed-speed. These units share the same water system to supply the building with cooled or heated water. Hybrid tandem, associating one inverter and one fixed-speed compressor, can better match the capacity requirement compared to a modular chiller with fixed-speed tandem compressors and increases efficiency.
Solar-powered air conditioning
Inverter compressors make solar-powered air conditioning viable. Before, fixed-speed on/off compressors required an inrush, or surge, current that was 4 to 6 times greater than the running current at startup, meaning a requirement of 4 to 6 times more solar panels or batteries. Inverter compressors start slowly and avoid this startup power which is needed each time a standard on/off compressor comes on.
Close control units
These are used in the cooling of IT and electronic equipment used in data centres, telecommunications and in manufacturing industries. Power management, energy consumption and heat loads are major challenges. Maintenance of a stable temperature and humidity control, compactness of the system and overall efficiency are key design challenges in these applications for ensuring data safety and availability. This is where inverter technology makes the difference.
Process cooling
In many industries the machinery and processes generate a large amount of heat which requires cooling, to protect the equipment and / or to ensure that the product being manufactured is of the required quality. Inverter technology helps to secure the process while providing greater efficiency.
Variable refrigerant flow (VRF)
VRF units are very popular cooling or reversible systems (heating and cooling). They combine the flexibility for building owners and occupants alike, with energy efficiency, high comfort, and ease of installation, without compromising on reliability. VRF systems already extensively use inverter technology. [3]

Challenges in adopting inverter scroll in HVAC systems

The compressor and drive need to be qualified to work together and for dedicated applications. The drive modulates the compressor speed and prevents it from operating out of the compressor operating limits. The inverter frequency drives need to use algorithms developed specifically for heating, ventilation and air conditioning (HVAC) or for refrigeration. They ensure that the system will run within the application constraints. The drive can also manage other devices such as oil injection valves or multiple compressors. As the compressor rotational speed changes, the amount of refrigerant — and oil — flowing through the compressor increases or decreases. The drive ensures that the compressor and bearings are optimally lubricated at all operating conditions by running the compressor in a suitable speed regime.

See also

References

  1. ↑ "IEEE MILESTONE (39) - Inverter Air Conditioners 1980-1981" (PDF). www.ieee.jp.org. March 2021. Archived (PDF) from the original on 29 December 2024.
  2. ↑ "Inverter Air Conditioners, 1980-1981 - IEEE Milestone Celebration Ceremony" (PDF). www.ethw.org. 16 March 2021. Archived (PDF) from the original on 7 April 2025.
  3. ↑ "HVAC Systems that Support Your Design Vision". Architect Magazine. Archived from the original on 2021-04-27. Retrieved 2023-01-01.
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