Operating Sequence Description - Electrolux EI30BM55HB Technical & Service Manual

Operation
Operating Sequence
Description
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, 120 volts A.C. is
supplied to the control unit. (Figure O-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.
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 O-2)
RELAY CONNECTED COMPONENTS
RY1 Oven lamp / Fan motor / Stirrer motor
RY2 Power Transformer
RY3 Turntable motor
2. 120 volts A.C. is supplied to the primary winding
of the power transformer and is converted to
about 3.3 volts A.C. output on the filament
winding, and approximately 2000 volts A.C. 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, secondary
interlock switch, and primary 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 compo-
nents 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 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. And contacts of the relay (RY1) open.
If the secondary interlock switch and primary
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, secondary interlock
switch, relay (RY1) and primary interlock relay
(RY2), causing the monitor fuse to blow.
2-2