초록 ▼

The invention uses a variable speed drive (VSD) only on a range of capacities corresponding from zero to standard point conditions, and if conditions correspond to higher than rated point current, the VSD is disconnected and the compressor is connected directly on line. This approach allows using a

The invention uses a variable speed drive (VSD) only on a range of capacities corresponding from zero to standard point conditions, and if conditions correspond to higher than rated point current, the VSD is disconnected and the compressor is connected directly on line. This approach allows using a smaller size VSD. At the same time, if there are several compressors operating in the same machine, only one VSD is needed. The VSD drives a first compressor from zero to the speed corresponding to the line frequency. Controls then switch the first compressor to direct on line (DOL) and disconnects the VSD from the first compressor. The VSD is then available to drive a second compressor. This process can be repeated through multiple compressors.

대표청구항 ▼

1. A method for controlling at least one compressor of a chiller system with a variable speed drive, comprising the steps of:a) checking to see if additional compressor capacity is needed by said system; b) ensuring said at least one compressor is running from said variable speed drive if additional

1. A method for controlling at least one compressor of a chiller system with a variable speed drive, comprising the steps of:a) checking to see if additional compressor capacity is needed by said system; b) ensuring said at least one compressor is running from said variable speed drive if additional compressor capacity is needed by said system; c) monitoring a current in said variable speed drive; d) closing an electronic expansion valve by a specified amount in said system if said current is greater than a specified percentage of a maximum current; e) increasing a frequency of said variable speed drive by a specified amount if said current is less than or equal to said specified percentage of said maximum current, f) checking to see if said additional compressor capacity needed by said system is satisfied by step (e); g) checking whether said frequency of said variable speed drive is equal to a frequency of line power powering said variable speed drive, and if not, performing steps (c) through (f) again; and h) transitioning said at least one compressor from variable speed drive to directly on line.