Electrolux EW27MO55HSA, Technical & Service Manual

Page: 13 / 48

Operation
2-1
The following is a description of component functions
during oven operation.
OFF CONDITION
Closing the door activates the stop switch, primary
interlock switch and secondary interlock switch.
(In this condition, the monitor switch contacts are
opened.) When oven is plugged in, 117 volts AC is
supplied to the control unit. (Figure 2-1).
1. The display will show “Enjoy your oven, 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.
NOTE: When door is opened, the oven lamp comes on.
COOKING CONDITION
Program desired cooking time touching the NUMBER
pads. When the START button 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 / Turntable motor
RY2 Power Transformer
RY3 Fan motor
2. 117 volts AC is supplied to the primary winding of
the power transformer and is converted to about
3.0 volts AC output on the filament winding, and
approximately 2360 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, third
door switch, monitor switch, door sensing switch, the
secondary interlock relay and the primary interlock
switch are activated with the following results. The
circuits to the turntable motor, the cooling fan motor,
and the high voltage components are de-energized,
the oven lamp remains on, 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 secondary interlock switch and
primary interlock switch and 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 primary interlock switch and secondary 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 secondary interlock switch and
door sensing switch close.
If relay (RY1) and the primary interlock switch fail with
their contacts closed when the door is opened, the
closing of the monitor switch contacts will form a short
circuit through the monitor fuse, the relay (RY1) and
the primary interlock switch, causing the monitor fuse to
blow.
Operating Sequence Description