IEC 61308-2005 pdf – High-frequency dielectric heating installations – Test methods for the determination of power output.
2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60050-841:2004, International Electrotechnical Vocabulary – Part 841: Industrial electroheat IEC 60519-9, Safety in electroheat installations – Part 9: Particular requirements for high-frequency dielectric heating installations 3 Definitions For the purposes of this document, the terms and definitions given in IEC 60050-841 and IEC 60519-9, as well as the following, apply. 3.1 type A equipment equipment with a dielectric heating generator independent of, or separable from, the applicator to which the high-frequency power is provided, for example, by a coaxial feeder 3.2 type B equipment equipment with a dielectric heating generator directly coupled to the applicator, for example, generator built into the plastic welding press NOTE In some cases, equipment with the dielectric heating generator directly connected to the heating chamber and inseparable from it can be treated as type A equipment. 3.3 useful output power – type A equipment maximum power measured in the test load described in this standard NOTE In this type, the output terminals of the generator are accessible, or the heating capacitor allows the use of the wet-sand test. In certain cases, the parts of the gluing or welding press can be disconnected, allowing access to the output terminals. The useful output power will be equal to, or greater than, the rated useful output power. 3.4 useful output power – type B equipment oscillating power calculated on the basis of measured values of voltages and currents NOTE The design of such equipment does not allow the connection of a test load.
4 Test loads 4.1 General There are four different types of useful output power test loads used in high-frequency dielectric heating installations. Only the main ones are outlined here. Specific constructions shall conform to known engineering techniques. The test loads should be constructed so as to reflect the characteristics of the working load as closely as practically possible. The calorimeter load, lamp load and resistive load allow the measurement of the output power of the dielectric heating generator. The wet-sand load allows the measurement of the useful output power of the dielectric heating installation (as defined in IEC 60519-9). For plastic welders, the test with the electrode defined in 3.5 allows the evaluation of the output power of the dielectric heating installation. 4.2 Calorimeter load A calorimeter load is used for measuring the useful output power when the load is assumed to be a combination of capacitance and resistance and for cases where the measured power is about 1 kW or greater. 4.3 Lamp load The lamp load is used to measure useful output power of up to about 1 kW. The matching of the load is accomplished by the selection of single-lamp power as well as by the connection of several lamps in parallel or in series. 4.4 Matched resistive load A matched resistive load can be used for applications where the load can be connected to the high-frequency output terminals. 4.5 Wet-sand load The load, which consists of a charge of wet sand placed in the heating capacitor, can be used for some applications where the high-frequency output terminals of the generator are not accessible.
5.2 Calorimeter load method Typical examples are shown in Figures 1 and 2, but variations of these designs are acceptable. The measuring element is composed of glass or a low power-loss material and comprises two electrodes manufactured from a non-magnetic material such as copper or aluminium. The generator output terminals are connected to the two electrodes and water serving as the power-absorbing medium flows through the charge. The electrode spacing may be adjustable for load-matching purposes. To achieve the correct impedance matching between the generator and the load, it may be necessary to use a tuning circuit, in order to obtain the required output power. A recommended water flow is about 1 l/min per kW but not less than 0,5 l/min per kW. To avoid local water temperature hot spots through the charge, the water shall be thoroughly mixed. To avoid the formation of steam, which may lead to explosion, the water flow should be monitored, for instance, by means of flow interlocking switches. The water inlet temperature shall not exceed 35 °C. The water outlet temperature shall not exceed 60 °C. The difference between the outlet temperature and the inlet temperature shall be at least 10 K in order to obtain measurement results of acceptable accuracy. The specific conductivity of the water shall be between 200 µS/cm and 600 µS/cm. The measurement shall be carried out when the load is in thermal equilibrium.