8
R-7A55(W)/(B)
R-7E45(W)/(B)
DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except during
convection cooking, grill cooking and dual cooking.
Damper position is set automatically by damper motor,
damper switch, damper cam and damper shaft.
These components are operated by a signal 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, Grill and Dual 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).
1-2. Contacts of shut-off relay (RY7) close, the damper
motor is energized, opening the damper door.
1-3. When the damper is moved to the open position by the
damper cam, damper switch is closed (ON position).
1-4. The signal of damper switch is re-sensed in the control
unit and shut-off relay (RY7) is turned off.
1-5. The A.C. 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
3. When oven is convection, grill or dual cooking:
3-1 Damper motor is energized right after the oven is
started.
3-2. 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.
3-3. The damper is held in the closed position during the
cooking operation
3-4. At the end of the cooking, shut-off 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 durining convection, grill or dual, or open
durning microwave, the control unit will stop oven
operation after 1 minute.
Cooking Mode
Operation of Damper
Microwave cooking
OPEN
Convection cooking
CLOSE
Grill cooking
CLOSE
Dual cooking
CLOSE
SENSING FIRE OPERATION
The oven will stop its operation when there is a fire in the
oven cavity in microwave cooking condition.
LSI measures the voltage across the temperature measure-
ment circuit intermittently within a 32-second time base after
since the oven is started in microwave cooking condition.
The oven will stop its operation when the difference of the
voltages is more than 0.3 volts in microwave cooking condi-
tion.
1. Within a 32-second base, first the thermistor is energized
for 3 seconds. After 2 seconds since the thermistor is
energized, the voltage across the temperature
measurement circuit is measured. And after 21 seconds
since the thermistor is cut off, the convection motor
operates for 10 seconds.
2. The oven carries out the procedure above again. If the
second voltage is 0.3V higher than the first voltage, LSI
judges it is a fire in the oven cavity and stops the oven.
3. When sensor cooking, the sensing fire operation is not
carried out until the oven senses the steam from food.
Because food cannot be cooked well by rotating the
convection fan at that time. After sensing the steam, the
sensing fire operation is started.
4. When LSI judges it is fire in the oven cavity, LSI will switch
off the relays to the power transformer, fan motor and
convection motor and LSI stops counting down. And then
the damper is closed so that the fresh air does not come
into the oven cavity.
CONVECTION
MOTOR
THERMISTOR
Sensing
Voltage
ON
OFF
ON
OFF
ON
OFF
0 2
20
30 32
64 (sec.)
3 sec.
Sensing the voltage across temperature measurement circuit.
10 sec.
