Sharp R-961 (W) - Page 14

FUNCTION OF IMPORTANT COMPONENTS
DAMPER OPEN-CLOSE MECHANISM
Damper position is set automatically by damper motor,
damper switch, damper cam and damper shaft.
These components are operated by a signa! that judges if
microwave cooking or other cooking operation is selected by
the CPU unit.
Microwave Cooking:
Damper is in the open position, because a portion of cooling
air is channeled through the cavity to remove steam and
vapors given off from the heating foods.
It is then exhausted at the top of the oven cavity into a
condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will be
allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in:
1-1. When power supply cord is plugged in, a signal is
sensed in the control unit, and operates shut-off relay
(RY7).
Contacts of shut-off relay (RY7) close, the damper
motor is energized, opening the damper door.
When the damper is moved to the open position by the
damper cam, damper switch is closed (ON position).
. The signal of damper switch is re-sensed in the control
unit and shut-off relay (RY7) is turned off.
. The AC. line voltage A.C. to the damper motor is
stopped and the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position
When oven is convection cooking:
Damper motor is energized right after the oven is
Started.
. When damper is in the closed position (damper switch
is OFF), its signal is sensed by the control unit, and shut-
off relay (RY7) is de-energized.
. The damper is held in the closed position during the
cooking operation
. At the end of any cooking, when the fan motor stops, the
relay (RY7) is energized and the damper is returned to
the open position.
NOTE: If the damper door is not in the proper position,
closed during convection, grill or dual, or open
during microwave, the control unit will stop oven
operation after 1 minute.
Operation of damper is shown below;
1-2.
1-3.
4.
Damper operation
Cooking condition Operation of Damper
Microwave Open
Convection Closed
Grill; during backed up with Closed
convection heating element
Grill; after convection heating Open
element back-up has stopped.
Dual (Microwave and Convection) Closed but open
when oven temperature above after 20 minutes
220°C is programmed
When oven temperature below Closed
200°C is programmed
Dual (Microwave and Grill) Open
Fire Sensing condition Closed
R-961 - 12
FIRE SENSING FEATURE
This model incorporates a sensing feature which will stop the
oven's operation if there is a fire in the oven cavity during
microwave cooking.
This is accomplished by the LSI repeatedly measuring the
voltage across the temperature measurement circuit (ther-
mistor) during it's 32-seconds time base, comparing the
obtained voltage measurements. If the most recent voltage
measured is 300mV greater than the previous voltage meas-
ured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the high voltage transformer, fan
motor and convection motor. The LSI also stops counting
down and closes the damper door so that no fresh air will
enter the oven cavity. Please refer to the following section for
a more detailed description.
Operation
Please refer to the timing diagrams below.
1. The thermistor operates within a 32-seconds time base
and it is energized for three (3) seconds and off for 29
seconds. Two (2) seconds after the thermistor is
energized, the voltage across the temperature
measurement circuit is sampled by the LSI and twenty
one (21) seconds after the thermistor is cut off the LSI
turns on the cooling fan for six (6) seconds.
. The above procedure is repeated. If the difference
between the first voltage measured (in step 1) and the
voltage measured when the procedure is repeated (step
2) is greater than 300mV the LSI makes the judgment that
there is a fire in the oven cavity and will switch off the
relays to the high voltage transformer, fan motor and
convection motor. The LSI also stops counting down and
closes the damper door so that no fresh air will enter the
oven cavity.
Once the fire sensor feature has shut the unit down, the
programmed cooking cycle may be resumed by pressing
the "START" pad or the unit may be resetby pressing the
"CLEAR" pad.
IMPORTANT:
During sensor cooking operation, the fire sensing op-
eration sequence will not begin until the AH sensor has
detected vapours and initiated a sensor cooking cycle.
This is because the operation of the convection fan
would interfere with the AH sensor's vapour detection.
0 21 9 64 (sec.)
CONVECTION
MOTO
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OFF 1
1
1
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1
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THERMISTOR
ON
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ON !
Sensing !
Voltage OFF
Sensing the voltage across temperature mezasurement circuit.
ROTISSERIE COOKING SYSTEN
All the surfaces of the food will be able to be sooked without
turning over, by rotating the food into which the skewer is
inserted.