Inverter compressor

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An inverter compressor is an inverter-operated gas compressor.

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

Video Inverter compressor

Market needs for variable capacity

Many cooling and air conditioning systems require reliable processes that are more efficient, compact, environmentally friendly, easy to install and maintain. Cooling requirements vary over a wide range during the day and throughout the year due to ambient conditions, occupancy and use, lighting etc.

In convenient cooling, it may also require stable and accurate temperature and humidity control in areas such as hospitals, IT & amp; telecommunication, cooling process. In applications such as schools, restaurants and office buildings, it is important that the cooling system is able to adapt to the shift of the extensive daily load.
In application processes such as fermentation, growing tunnels, and industrial processes, accurate temperature setting is required to secure production quality.

Maps Inverter compressor

Different modulation technologies

There are several ways to modulate the cooling capacity in the cooling system or air conditioning and heating. The most common in air conditioners are: on-off cycling, hot gas bypass, use or not of fluid injection, manifold configuration of some compressors, mechanical modulation (also called digital) and inverter technology. Each has advantages and disadvantages.

Cycled off: The results in shutting down a fixed-speed compressor are in mild load conditions and may result in short cycles and decreased compressor life. The efficiency of the unit is reduced by cycling pressure and temporary loss. Turndown capacity is 100% or 0%
Hot gas passenger: Involves injecting a certain amount of gas from the discharge to the suction side. The compressor will still operate at the same speed but thanks to bypass, the mass flow of the circulating refrigerant with the system is reduced and thus the cooling capacity. This naturally causes the compressor to run in vain during the period in which the bypass operates. Turndown capacity varies between 0 and 100%.
Configure manifold: Some compressors can be installed in the system to provide peak cooling capacity. Each compressor can run or not to perform the cooling phase of the unit capacity. Turndown capacity is 0/33/66 or 100% for trio configuration and 0/50 or 100% for tandem.
The compressor is mechanically modulated: This internal mechanical capacity modulation is based on a periodic compression process with a control valve, set of 2 separate moving windings stopping compression for a certain period of time. This method varies the flow of refrigerant by changing the compression time average, but not the actual motor speed. Despite an excellent turndown ratio - from 10 to 100% cooling capacity, mechanical modulation rolls have high energy consumption because the motor is running.
Inverter compressor: Using external variable-frequency drives - to control the speed of the compressor. The refrigerant flow rate is changed by changes in the speed of the compressor. The power-on ratio depends on system and manufacturer configuration. It modulates from 15 or 25% to 100% at full capacity with a single inverter of 12 to 100% with a hybrid tandem.

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Working principle

The variable-frequency drive controls the speed of the compressor motor. The compressor is specially designed to run at different motor speeds to modulate the cooling output. Variable speed operations require the right compressor for full speed operation and special compressor lubrication systems. Proper oil management is an important requirement to ensure compressor life. Appropriate oil management provides the correct lubrication for the scroll set at low speed and prevents the excess oil from being injected into the circuit when operating at full speed.

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Apps

The variable speed technology can be implemented in HVACR, close control and process cooling applications and as diverse as packaged or split air conditioning units, roofing, cooling, precision cooling, VRF and condensing units.

Roof: This is a very common unit type. Increased energy costs mean that AC manufacturers must develop a new generation of high-efficiency, cost-effective air conditioning for commercial buildings that meet or exceed standard load-efficiency standards of 18 IEER normally. The goal is to reduce energy use by 30% compared to current equipment. Inverter technology helps OEMs to build units that meet this demand.
Air handling unit: It has integrated cooling that is used in commercial applications for temperature and humidity settings in various ranges of buildings such as small office buildings, gyms and medical centers. The inverter compressor solution enables seamless modulation and enormous energy savings.
Modular cooler: A typical modular chiller installation uses a lot of fixed speed. These units share the same water system to supply buildings with water that is cooled or heated. The hybrid tandem, which connects one inverter and one fixed speed compressor, can better meet capacity requirements compared to a modular chiller with a fixed speed tandem compressor and improves efficiency.
Close control unit: It is used in IT cooling and electronic equipment used in data centers, telecommunications, and in the manufacturing industry. Power management, energy consumption and heat load are the main challenges. Maintenance of stable temperature and humidity control, system cohesiveness and overall efficiency are key design challenges in this application to ensure data security and availability. This is where inverter technology makes a difference.
Cooling process: In many industries machines and processes produce large quantities of heat that require cooling, to protect equipment and/or to ensure that the products produced are of the required quality. Inverter technology helps secure the process while delivering greater efficiency.
Flow of variable refrigerant (VRF): The VRF unit is a very popular cooling or reversible (heating and cooling) system. They combine the flexibility to build owners and occupants, with energy efficiency, high comfort, and ease of installation, without sacrificing reliability. VRF systems are already using inverter technology.

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Challenges in adopting inverter windings in HVAC system

Compressors and drives must be eligible to work together and for specific applications. The drives modulate the speed of the compressor and prevent it from operating within the limits of the compressor operation. Drive frequency inverters need to use algorithms developed specifically for heating, ventilation and air conditioning (HVAC) or for cooling. They ensure that the system will run within application boundaries. These drives can also manage other devices such as oil injection valves or some compressors. When the compressor turn speed changes, the amount of refrigerant - and oil - flows through the compressor increases or decreases. Drive ensures that the compressor and bearings are optimally lubricated at all compressor speeds.