| 摘要 |
The invention relates to an induction heater for heating annular articles, and includes a U-shaped transformer core (1) and a magnetic yoke which can be lifted from the transformer and upon which the article to be heated can be fitted. When heating the article, mains current is supplied to a primary core (2) on the transformer core, via a first switch (4). In accordance with the invention, the switch (4) is connected in parallel with a PTC-resistor (5, or 5 min ) which when the switch (4) is broken, upon completion of the heating period, first conducts the primary current, which gradually decreases to an extremely low value of about 10 mA, due to the heating of the PTC-resistor (5,5 min ), causing demagnetization of the heated article. |
