| 摘要 |
In order to limit the disturbance to the mains supply caused by periodic energisation and de-energisation of a resistive load such as the heater of the grill of an electric cooker, the heater is split into two heating elements which are energised alternately each for a period of time set by a user operable control 2. The mark to space ratio of the energisation of the partial loads 1a and 1b is varied in dependence upon the setting of the control 2. In order to provide fast response when the apparatus is first turned on, circuitry 16 overrides the proportion of control and energises both loads 1a and 1b simultaneously for a predetermined period of time long enough to bring the heater up to its working temperature. Means are also disclosed to isolate the heaters in the event of failure of the triacs which control their energisation. |
