Menno's
By Menno Hochstedler
Microwaves Pt. 2
I will use information that is
familiar to me, and there are other
technicians out there that garner their
own information helpful to them.
Last month we created an article on
the results or benefits of microwave
energy. This article will be about how
the microwave energy is created, allowing for variables, as information may
differ from one microwave to the next.
Since metal does not allow microwaves
passage through it, it becomes the
material of choice for containment.
Since the microwaves are short and
of a certain size that cannot bend, we
are allowed to see food cooking inside
the oven through correctly sized holes
in the door. If there is a flawed hole or
anything that causes imperfections
in the oven cavity, there will be arcing
that will render the unit unsafe to use.
All the components in the microwave oven are working together to get
the correct energy to the magnetron so
it can produce microwaves. The magnetron needs approximately 4000 volts
to go into oscillation to generate the
microwaves. The microwave has two
basic sections, the low voltage side that
controls the cycle and safety features,
and the high voltage side that creates
the energy for the magnetron. The high
voltage transformer or the new style
inverter is the component that separates the two sections.
The low voltage side takes the 120
volts, passes it through all the safety
devices like thermal and other fuses.
It also passes through the interlock
switches that respond to door position,
allowing power to the control device.
On older style models the control device was a manual timer and a variable
switch, then along came the PCB control boards that perform the functions.
Fans, turntables, lights, low voltage
side of high voltage transformer, and
pg 28 · The Hometown Treasure · Dec. ‘11
Tech Minutes
some stirrers are powered from the low
voltage side also.
The high voltage side consists of
the high voltage transformers output
side, the doubling circuit, and the magnetron. The high voltage transformer
takes the 120 volts from the low voltage section and increases the voltage
to approximately 2000 volts and feeds
it to the doubling circuit. The doubling
circuit consists of the high voltage capacitor and the high voltage diode. The
high voltage diode converts the voltage
to direct current and the capacitor discharges the 2000 volts and sends it to
the magnetron. This adds to the 2000
volts that comes directly from the
high voltage transformer, giving the
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