GB816621A - Improvements in or relating to high frequency heating equipment - Google Patents

Abstract

816,621. High frequency heating. RADIO HEATERS Ltd. Nov. 13, 1957 [Oct. 10, 1956], No. 30894/56. Class 39(3) In high frequency heating apparatus of the kind in which cooling water is circulated through coils, or through or around other components, condensation on the external surface of the water cooled components is reduced by stopping the circulation of the water through the apparatus when the high frequency power is switched off. An electromagnetically operated water valve in the circulation path of the primary and secondary coils of an H.T. transformer, has a coil A, and energization of a contactor coil B causes contacts in the H.T. circuit (not shown) to be closed. To bring the apparatus into operation, an "on" button 2 is pressed to complete a circuit through contacts D<SP>1</SP> of a hold-out relay D which prevents chattering of the contacts of an overload trip 6, through the contacts C<SP>1</SP> associated with a surgelimiting contactor coil C, and through the coils A, B. Energization of the water valve coil A allows the cooling water to flow, and the high frequency generator is energized by energization of the contactor coil B. Contacts B<SP>1</SP>, B<SP>2</SP> are closed and current then flows through the surgelimiting contactor coil C which is slow to operate, and after an interval, a surgelimiting resistor in the H.T. circuit is shortcircuited; the opening of contacts C<SP>1</SP> on energization of the coil C has no effect since contacts A<SP>1</SP> have already been closed. The apparatus continues to operate, but if the trip contacts 6 or the water valve contacts A<SP>1</SP> are opened, the coils A, B become de-energized so that H.T. will be removed from the generator and the flow of cooling water will be stopped. A water pressure switch (not shown) and an "off" button 4 are included in the circuit, and separate water valves may be provided for the primary and secondary coils.