Patent ID: 7408320
Filing Date: 2008-08-05
Classification: H02M,H02P

Abstract:
1. Apparatus for controlling the power of an AC supply voltage supplying an electric motor by phase control and for reducing harmonics caused by said phase control, comprising a first switching element connected in series with said electric motor and driven at a first firing angle into a conducting state by a control device for performing a phase control of said electric motor during a given half cycle of the AC supply voltage, and a second switching element and a resistor element both being electrically connected in series to form a series connection, said series connection being connected in parallel to the first switching element, said control device driving the second switching element at a second firing angle into a conducting state at a first point in time (t 1 ) during said given half cycle that is shortly before a second point in time (t 2 ) when the first switching element is driven into the conducting state; the improvement comprising a fan coupled to said electric motor for generating an airflow to cool said electric motor, and arranging said resistor element in said airflow to cool the resistor element.