12
CIRCUIT DESCRIPTION
1. When the food is placed in the oven cavity and door is closed.
• The contact of the interlock monitor switch open (NO).
• 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.
• 230V 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 filamente winding of the high voltage transformer. This fila-
ment voltage is applied to the magnetron to heat the magnetron filament through two noise pre-
venting 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 chargy 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.
15A Fuse
Timer Motor
TM
TM
Cavity Lamp
CL
Geard Motor
GM
Fan Motor
FM
CL
GM
FM
Secondary
Interlock
Switch
Interlock
Monitor
Switch
NO
NC
COM
Primary
Interlock
Switch
Timer
Switch
Fig. 1