| 摘要 |
PROBLEM TO BE SOLVED: To provide an overload preventing device for a centrifugal compressor capable of displaying capacity of an electric motor for drive to an allowable maximum limit by taking characteristics, influenced by the suction fluid temperature of the centrifugal compressor, into account. SOLUTION: An overload preventing device comprises a load detecting means 10 to detect the current of an electric motor 4; a temperature detecting means 11 to detect the suction air temperature of a centrifugal compressor 1; a memory means 12 to store an ambient temperature and relation information of the allowable maximum current of the electric motor 4 to the ambient temperature a load regulating valve 6 situated in the feed and exhaust flow passage of the centrifugal compressor 1 and regulating a compressor load by stages at least in two stages or in no stage and a load control means 13 for presuming that a detecting temperature value from the temperature detecting means 11 is equal to the ambient temperature of the electric motor 4, comparing the allowable maximum current of the electric motor 4, determined by the ambient temperature of the electric motor based on memory information of the memory means 12, with a detecting current from the load detecting means 10, deciding that overload operation occurs when the detecting current is higher, and regulating the load regulating valve 6 to the unload side.
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