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1. When the food is placed in the oven cavity and door is closed.
• The contact of the interlock monitor switch open.
• The contacts of the primary interlock switch and secondary interlock switch close.
2. When the timer is set to the time desired.
• The contact of the timer switch close.
• Oven lamp turn on.
• 120V AC is applied to the high voltage transformer.
• Turntable motor start rotating and glass tray rotating.
• Fan motor rotating and cools the magnetron by blowing air.
• Timer motor operating and point to passing cooking time.
• 3.3 Volts AC is generated from the filament winding of the high voltage transformer. This filament voltage is applied to
the magnetron to heat the magnetron filament through two noise preventing choke coils.
• A high voltage of 2000 Volts AC is generated in the secondary of high voltage transformer and this secondary voltage
is increased by the action of the diode and the charging of the high voltage capacitor. This resultant D.C voltage is then
applied to the anode of the magnetron. As shown in Fig. 2 the first half cycle of the high voltage produces in the high
voltage transformer secondary charges the high voltage capacitor. Current flow is in the direction of the dotted-line
during the second half cycle, the voltage produced by the transformer secondary, and the charge of the high voltage
capacitor are combined and applied to the magnetron as shown by the solid line so that oscillations begins.
The disturbance wave generated by the magnetron is prevented by the choke coils of 1.5µH, filter capacitors of 500pF
and the magnetron’s shielded case so that TV and radio programs are not impaired by noise.
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CIRCUIT DESCRIPTION
TM
TM
CL
CL
GM
GM
FM
FM
Timer motor Cavity lamp Geard motor Fan motor
Fig. 1
15A Fuse
Primary
Interlock
Switch
Interlock
Monitor
Switch
Timer
Switch
Secondary
Interlock
Switch