| 摘要 |
PURPOSE:To positively detect the degree of frosting to an outdoor heat exchanger by detecting a current variation value of a compressor current by a current detection circuit when a blower for the outdoor heat exchanger is stopped for a predetermined period of time or is driven at a low rotational speed. CONSTITUTION:During a room heating mode operation, the outdoor blower 4 is stopped for a predetermined period of time, and the variation of the current of the compresser 1 flowing to a current transformer 20 immediately before the stoppage of the outdoor blower 4 and the restarting of the operation, is measured. The quantity of frosting is estimated from the variation width DELTAA to carry out a defrosting control. That is, defrosting is prohibited during a time T1 from the starting of the heating mode operation, and thereafter the current sampling is carried out in a period T2 to continue the heating operation until the operation reaches the quantity of frosting requiring defrosting, that is, the current variation width DELTAA becomes smaller than the preset value Ax. Therefore, it is possible to set the quantity of frosting upon entering the defrosting operation at a substantially constant value, and hence the defrosting operation can be carried out by the time control. |
