| 摘要 |
PURPOSE:To limit the pressure of a compressed gas to a fixed value or lower, and to improve the reliability of a compressor largely by bringing the detecting value of the DC currents of an inverter section within a limiting value changing ion the form of the linear expression of the number of revolution. CONSTITUTION:Input DC voltage V and input DC currents I are taken in by a control circuit 6, and inputted to an overload detecting circuit in the control circuit. On the other hand, drive signals N corresponding to the predetermined number of revolution are transmitted over an inverter section 3 by the control section 6. An output from the inverter is fed to an adjustable speed motor 4, and a compressor 7 is driven. DC currents are controlled within a limiting value, which can be described by the linear expression of the number of revolution of the compressor, thus keeping the pressure of a discharge gas within a prescribed value. Accordingly, the safety of a cycle can be improved largely while there is not trouble on actual application such as the lowering of capability even when the conditions of load and the conditions of input voltage change on heating operation, thus extremely suppressing a burden on the compressor. |
