| 摘要 |
PURPOSE:To secure the quantity of air current enough for substantially keeping a required heat-exchange ability by a procedure in which when one of a plurality of air feeding fans is in a fault, the remaining fans are changed over to high speed driving. CONSTITUTION:In a case where one of the air feeding fans 42a and 42b gets fault and stops its operation, an output from a rotational speed detecting sensor such as a tachometer disposed on the rotational shaft of the fan is used as an input signal to carry out a fault detection, relay contacts 6a and 6b are opened, and the fans on the fault side is removed from a power supply circuit, and a control signal is applied to an inverter 7. The output frequency is raised, and the remaining sound fans are rotated at high speeds and a quantity of air flow substantially equals to that obtained by all of the fans, can be secured. |
