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Sunday, 24 July 2016

Inverter technology based Refrigerators and Air-conditioners

"Regular or traditional refrigerators and air-conditioners usually have a single speed compressor that runs on a fixed speed. These compressors are either ‘ON’ or ‘Off’ state depending on the temperature inside the refrigerator or room and the thermostat’s setting." 
Basically the compressor of traditional refrigerator has induction motor. Because of the high pressure of compressor, the motor acts as "a motor with blocked rotor" at start, and therefore draws a heavy current (usually 3 to 4 times the normal running current) during starting. These compressors start and stop depending on the temperature inside the refrigerator.

The thermostat switches the compressor ‘ON’ when the temperature inside the refrigerator or ambient temperature inside the room rises above the desired temperature and vice-versa. 

" For example, a regular 1.5 ton fixed speed Air-conditioner requires a starting current of approximately 30 A which is 3 times its normal running current of 10 A." 

Hence regular refrigerators and air-conditioners are not suitable for running on inverters or solar PV systems. Or in other words they require an inverter of very high capacity. 

" For example a 1.5 ton normal air-conditioner will need an inverter of at-least 5 kVA capacity."

How Inverter technology based refrigerators and Air-conditioners are different?

The inverter technology based refrigerators and Air-conditioners have variable speed motors that start up gradually resulting in a much reduced starting current. These compressors are always ‘ON’ and change their speed depending on the temperature requirement.

An inverter technology based air-conditioner of 1.5 ton needs only 6 to 7 A during normal running and the starting current is also much less compared to the traditional air-conditioner. Thus an inverter of 2 or 3.5 kVA would be enough for operating a 1.5 ton air-conditioner. Reduced initial current results in reduced wear and tear of parts i.e. increased component life and hence of the refrigerators and air-conditioners. This also reduces the sharp current fluctuations that the compressor places on the power supply. In addition, the inverter technology based compressor will have higher power factor which results in lower electricity consumption. 

Initial cost and Energy saving with Inverter technology Refrigerators and Air-conditioners:

Although the initial cost of inverter technology based refrigerator and air-conditioner is approximately 40% higher than the traditional one but there is a 30% reduction in energy bill. These refrigerators and air-conditioners are more suitable to be operated on a solar PV system as the required inverter capacity will be very low.