A compressor system includes a pair of compressors located in a common
shell. A common drive shaft drives both compressors and the drive shaft
is powered by a single motor. One or both of the compressors can be
equipped with a pulse width modulated capacity control system and a vapor
injection system. When one compressor is equipped with these systems, the
capacity can be varied between 50% and 110%. When both compressors are
equipped with these systems, the capacity can be varied between 0% and
120%.