| 摘要 |
<p>Apparatus is described for controlling an electric heater incorporating at least one electric heating element (2A, 2B, 2C) and energised from a single voltage alternating current supply (8). The apparatus includes a control knob (15) for manually selecting any one of a predetermined number of power settings for the heater from the voltage supply (8), the power settings varying progressively between a minimum power setting and a maximum power setting. The apparatus further includes a controller (10) adapted and arranged to supply to the electric heater within a predetermined constant time interval in each power setting a first dissipated power level and a second dissipated power level. The first dissipated power level comprises a first selected proportion of half cycles in a predetermined number of half cycles of the voltage supply and the second dissipated power level comprises a second selected proportion of half cycles in a predetermined number of half cycles of the voltage supply. In a plurality of power settings the second selected proportion is different to the first selected proportion. There is no more than one change between the first and second dissipated power levels within the predetermined constant time interval. <IMAGE></p> |
