Frigidaire CFMV152KW, Servicing Manual

Page: 13 / 52

Section 2 Operation
2-1
The following is a description of component functions
during oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and
secondary interlock 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 “WELCOME, PRESS CLEAR
AND PRESS CLOCK”. To set any program or set the
clock, you must first touch the STOP/CLEAR button.
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
RY2 Power Transformer
RY3 Cooktop Lamp
RY6 Hood Fan 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 2200 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, 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 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, door sensing
switch, and primary interlock 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 and
door sensing switch close. And contacts of the
relay (RY1) open.
If the primary interlock switch and secondary interlock
relay (RY2) fail with the contacts closed when the door
is opened, the closing of the monitor switch contacts will
form a short circuit through the monitor fuse, primary in-
terlock switch, relay (RY1) and secondary interlock relay
(RY2), causing the monitor fuse to blow.
Operating Sequence Description