Multi-type air-conditioning system with an outdoor unit coupled to a plurality of indoor units

A multi-type air-conditioning system with an outdoor unit coupled to a plurality of indoor units comprising:

• an inverter to provide output power of a given frequency, said inverter being mounted in said outdoor unit;
• a compressor motor starting to run in response to the receipt of said output power from said inverter, and whose running speed is variable according to the frequency of said output power from said inverter, the compressor motor being mounted in said outdoor unit;
• a capacity-variable compressor driven by said compressor motor to take in refrigerant, compress thereof, an deliver said compressed refrigerant, said capacity-variable compressor being installed in said outdoor unit;
• an outdoor heat exchanger to interchange the heat of inflow refrigerant with the heat of outdoor air, said outdoor heat exchanger being mounted in said outdoor unit;
• a plurality of indoor heat exchangers, each to interchange the heat of inflow refrigerant with the heat of indoor air, said plurality of indoor heat exchangers being provided respectively in said plurality of indoor unit;
• a plurality of flow control valves, each to control the flow of refrigerant running through each of said plurality of indoor heat exchangers;
• a refrigeration cycle with said capacity-variable compressor, said outdoor heat exchanger, each of said plurality of flow control valves, and each of said plurality of indoor heat exchangers coupled together and held in combined service;
• means to detect an air-conditioning load of each of said indoor units;
• means to separately select a target opening (.theta.t) of each of said plurality of flow control valves according to said air-conditioning load of said each indoor unit;
• means to fully open the flow control valve which will have a maximum target opening (.theta.t.sub.max) selected out of individual said target openings;
• means to increase an actual opening (.theta.) of each of those flow control vales, other than said flow control valve due to be fully opened, by a given value (.DELTA..theta.);
• means to select a target frequency (Ft) of output power from said inverter according to the total of respective air-conditioning loads of said indoor units;
• and
• means to lessen an actual frequency (F) of said output power of said inverter lower than said target frequency (Ft) by a given value (.DELTA.F).