Abstract

The mathematical analysis of the compressor unit operation with a stepwise capacity control, with the assumption of under critical air uptake, is incorporaled in the paper. The relatiónships between the parameters characterising the pressure course in the air tank as a function of dimensionless parameters with the air uptake depending on pressure change have been derived. The formulate on the frequency of switching the compressor into idling and on its maximum value is also given in the paper. In the adopted model  of the air uptake only a small impact of the pressure changes on values of time  of the pressure rise and  full period of pressure change was proved as well as on the mean value of the air pressure uptakes users. Simple dimensionless relations allowing for the comparison of the of the compressor units with various stepwise control system have also been derived. An experimental verification of some of the relationships was carried out as well.