Electrolux FMV156EMC, Service Manual

Page: 9 / 48

9
FMV156EMC
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
the following is a description of component functions dur-
ing 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, 10 volts A.c. is supplied to the
control unit. (Figure o-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 pad. the display will clear, and " : "
will appear .
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 o-)
RElAY coNNEctED coMPoNENtS
RY1 oven lamp / Fan motor / Stirrer motor
RY Power transformer
RY3 turntable motor
RY4 Hood fan motor
. 10 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
000 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
channelled through the waveguide into the cavity feed-
box, 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
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.
() 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
(RY) 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 interlock switch,
relay (RY1) and secondary interlock relay (RY), causing
the monitor fuse to blow.
POWER LEVEL P-0 TO P-90 COOKING
When Variable cooking Power is programmed, the 10
volts A.c. is supplied to the power transformer intermittently
through the contacts of relay (RY) which is operated by the
control unit within an interval second time base. Microwave
power operation is as follows:
VARI-MoDE oN tIME oFF tIME
Power 10(P-HI) 3 sec. 0 sec.
(100% power)
Power 9(P-90)
30 sec. sec.
(approx. 90% power)
Power 8(P-80) 6 sec. 6 sec.
(approx. 80% power)
Power 7(P-70)
4 sec. 8 sec.
(approx. 70% power)
Power 6(P-60) sec. 10 sec.
(approx. 60% power)
Power 5(P-50) 18 sec. 14 sec.
(approx. 50% power)
Power 4(P-40) 16 sec.
16 sec.
(approx. 40% power)
Power 3(P-30)
1 sec. 0 sec.
(approx. 30% power)
Power (P-0)
8 sec. 4 sec.
(approx. 0% power)
Power 1(P-10)
6 sec. 6 sec.
(approx. 10% power)
Power 0(P-0)
0 sec. 3 sec.
(0% power)
Note: the oN/oFF time ratio does not correspond with the
percentage of microwave power, because approx.
seconds are needed for heating of the magnetron
filament.