BS 7509:1995 Industrial microwave heating installations. Test methods for determination of power output
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1.1 Scope and object
This International Standard is applicable to industrial microwave heating installations used
for the purpose of thermal applications of loads containing water or moisture such as
heating, drying of partially conductive or non-conductive materials, such as wood, textiles,
paper, foodstuffs, etc., in both normal and protective atmospheres, using for example,
inert gas or vacuum. For other loads (for example, plastics) the test methods are under
consideration.
This standard relates to microwave power generators in the frequency range 300 MHz to
6 GHz comprising an assembly of electrical and mechanical devices intended for the
transfer of microwave power to the material to be treated.
Equipment operating at the lower end of the microwave frequency spectrum (i.e. between
300 MHz and about 600 MHz) may use vacuum tubes or alternative microwave emitters.
If the power output meas rement systems specified in this standard cannot be applied for
particular applications within this frequency range, then the alternative systems would be
those of IEC 1308.
The main purpose of this standard is to give test methods for industrial microwave energy
generators. Due to the large variety of microwave heating applications, any output power
figures obtained as a result of these tests should not be taken as representing the amount
of power that can be dissipated into a particular product within a particular microwave
heating installation, but in certain instances, the output figures could be used as an indi-
cation of performance.
The amount of power required to achieve an aim for enthalpy change in a product within a
fixed period of time will be dependent, for example, on the product's composition, the
evolution of its loss factor with temperature, as well as the construction of the applicator
system, the way the generator is matched to the product within the applicator and the
amount of coupling be een generators when more than one is used.
Two types of microwave industrial heating equipment exist:
Type A
Equipment with microwave power generators (for example, power supplies plus
magnetrons or klystrons), independent of or separable from the applicators, to which
they provide the microwave power, for example via a waveguide or a coaxial feeder.
This is mostly the case when high-power magnetrons or klystrons are used. Usually,
a circulator is mounted between the magnetrons or klystrons and the applicator to
protect them from reflected power.
[Type B
Equipment with microwave power generators directly coupled to the applicator, i.e.
inserting a circulator or a water load between the generator or generators and the
applicator itself, becomes structurally impossible.
This standard relates to equipment normally operating under continuous rated conditions.
