Inverter air conditioner

The inverter tag found on some air conditioners signifies the ability of the unit to continuously regulate its thermal transfer flow by altering the speed of the compressor in response to cooling demand.Traditional reverse-cycle air conditioners use a compressor that is either working at maximum capacity or switched off in order to regulate the temperature of the room. A thermostat is used to measure the ambient air temperature and switch the compressor on when the ambient air temperature is too far from the desired temperature.An alternate way to meet the varying cooling demand is to have the ability to vary the capacity of the compressor or as its technically called "modulate" the capacity. An air conditioner compressor has two components, a mechanical part - the actual compressor and the electrical part - the motor to drive the compressor. Either of the components can be used to "modulate" the capacity. In Digital Scroll compressors - the mechanical Scrolls of the compression mechanism is controlled to "modulate" and the electric motor runs at constant speed. The other method is to control the speed of the compressors by various means.Air conditioners bearing the inverter tag use a variable-frequency drive to control the speed of the motor and thus the compressor. The variable-frequency drive uses a rectifier to convert the incoming AC current to DC and then uses pulse-width modulation of the DC current within an inverter to produce AC current of a desired frequency. The AC current is used to drive a brushless motor or an induction motor. As the speed of a brushless motor is synchronized to the frequency of the AC current, it is thus possible to build a compressor that can be run at different speeds. Similarly, the voltage and frequency can be varied as needed to run an induction motor at different speeds. A microcontroller can then sample the current ambient air temperature and adjust the speed of the compressor appropriately. All this electronics of course does add to the complexity and comes at a cost, significant being the conversion losses from AC to DC and then back to AC which can be as high as 4 - 6% for each conversion step.Eliminating stop-start cycles increases efficiency, extends the life of components, and helps eliminate sharp fluctuations in the load the air conditioner places on the power supply. Ultimately this makes inverter air conditioners less prone to breakdowns, cheaper to run, and the outdoor compressor is generally quieter than a standard air conditioning unit's compressor.[1]While at the beginning of the 1990s inverter air conditioners had some drawbacks,[2] these have been mostly overcome - the conversion losses are lower, sophisticated electronic filters are able to mask out most of the electromagnetic interference generated in Inverters. Running at full load, a compressor delivers its best efficiency and outperform inverters. Inverter-based air conditioners have their strengths in environments where a partial load is common, as they are significantly more efficient than conventional air conditioners in those situations. For conventional households where each outdoor unit is connected to a single dedicated indoor unit, inverters are the preferred option, as partial loading is the common mode there. The higher initial expense is balanced by lower energy bills. In a typical setting the pay-back time is about two years (depending upon the usage). For more modern installations where an outdoor unit is connected to multiple indoor units there are some better options also available nowadays.Therefore, which type will be better depends on usage. In any case though, it pays to buy an energy efficient model, i.e. one with a high SEER, EER, or HSPF factor and at least an EnergyStar certified product, as this will significantly reduce the electricity bill.The inverter principle has been applied to a wide range of household appliances, including microwave ovens, washing machines, and so on.

Source : http://en.wikipedia.org/wiki/Inverter_%28air_conditioning%29