Section 2 Operation; Operating Sequence Description; Off Condition; Cooking Condition - Frigidaire CGMV173KB Servicing

Operating Sequence Description

The following is a description of component functions
during oven operation.

OFF CONDITION

Closing the door activates the stop switch (door sensing
switch) secondary interlock switch and third door
switch. (In this condition, the monitor switch contacts
are opened.) When oven is plugged in, 120 volts AC is
supplied to the control unit. (Figure 2-1).
1. The display will show "ENJOY YOUR OVEN PRESS
CLEAR". To set any program or set the clock, you
must first touch the CLEAR/OFF pad. The display
will clear, and " : " appears.

COOKING CONDITION

Program desired cooking time touching the NUMBER
pads. When the START pad is touched, the following
operations occur:
1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure 2-2)
RELAY CONNECTED COMPONENTS
RY1 Oven Lamp / Fan motor / Stirrer motor
RY2 Power Transformer
RY7 Turntable motor
2. 120 volts AC is supplied to the primary winding of
the power transformer and is converted to about
3.3 volts AC output on the filament winding, and
approximately 2000 volts AC on the high voltage
winding.
3. The filament winding voltage heats the magnetron
filament and the H.V. winding voltage is sent to a
voltage doubler circuit.
4. The microwave energy produced by the magnetron
is channeled through the waveguide into the cavity
feedbox, and then into the cavity where the food
is placed to be cooked.
5. Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped. The
oven will revert to the OFF condition.
6. When the door is opened during a cook cycle,
monitor switch, door sensing switch, primary
interlock switch, third door switch and secondary
interlock relay are activated with the following
results. The circuits to the stirrer motor, the cooling
fan motor, the turntable motor, and the high voltage
components are de-energized, and the digital read-
out displays the time still remaining in the cook cycle
when the door was opened.
7. The monitor switch is electrically monitoring the
operation of the primary interlock switch, and stop
switch (door sensing switch) is mechanically
associated with the door so that it will function in
the following sequence.
(1) When the door opens from a closed position,
the secondary interlock relay, stop switch (door
sensing switch) and primary interlock switch and
third door switch open their contacts, and then
the monitor switch contacts close.
(2) When the door is closed from the open position,
the monitor switch contacts open first. Then the
contacts of the primary interlock switch, stop
switch (door sensing switch) and third door
switch close. And contacts of the relay (RY1)
open.
If the primary interlock switch fails with the contacts
closed when the door is opened, the closing of the
monitor switch contacts will form a short circuit through
the C/T fuse, primary interlock switch and relay (RY1)
causing the C/T fuse to blow.

Section 2 Operation

2-1