| 摘要 |
The windings of an electromagnetic device for heat-sealing thermoplastic material having an electrically conductive layer are included as an inductive component in an oscillatory circuit, rather than merely being an external load. Two inductively coupled windings operate as a feedback element to control the alternate conduction of two transistors, to produce an oscillating signal. The core of the electromagnetic heating element has a E-shaped cross section, and the windings are wound around the middle limb of the core and are substantially surrounded by the two outer limbs to thereby substantially reduce thermal losses.
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