Sharp R-8R51 - Page 7

VARIABLE COOKING
When the microwave oven is preset for variable cook-
ing power, the line voltage power is supplied to the
power transformer intermittently within a 32-second
time base through the relay contact which is coupled
with the current-limiting relay RY2. The following lev-
els of microwave power are given. SETTING
séc
24 sec. ON 8 sec. OFF
MEDIUM HiGH Approx 70% > 595 Watts
18 sec ON +4 sec. OFF
MEDIUM | Aprox. 50% - 425 Wants
12 sec ON 20 sec. OFF
MEIDUN LOW Approx. 30% - 255 Watts
30 sec. OFF
6 sec. ON
NOTE: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 2 seconds
are needed for heating up the magnetron fila-
ment.
CONVECTION COOKING CONDITION
PREHEATING CONDITION (Figure 0-3)
Program desired convection temperature by touching
the @ fp (CONVECTION MODE) key.
When the START key is touched, the following
operations occur:
1. The coil of shut-off relays RY1, RY6 and RY7 are
energized, the oven lamp, cooling fan motor,
turntable motor and convection motor are turned
on.
2. The coil of relay RY5 is energized by the control
unit. The damper is moved to the closed position,
opening the damper switch contacts.
The opening of the damper switch contacts sends
a signal to the LSI on the control unit de-energizing
the relay RY5 and opening the circuit the damper
motor,
3. The coil of shut-off relayRY3 is energized by the
control unit and the mains supply voltage is added
to the convection heating element.
4. When the oven temperature reaches the selected
preheat temperature, the following operations oc-
cur
4-1. The shut-off relay RY3 is de-energized by the
control unit temperature circuit and
thermistor, opening the circuit to the con-
vection heating element.
4-2. The oven will continue to function for 15
minutes, turning the convection heating ele-
ment on and off, as needed to maintain the
selected preheat temperature.
The oven will shut-down completely after 15
minutes.
CONVECTION COOKING CONDITION
(Figure 0-3}
When the preheat temperature is reached, a beep signal
will sound indicating that the holding temperature has
been reached in the oven cavity. Open the door and
place the food to be cooked in the oven. Program de-
sired cooking time and convection temperature by
touching the @ fb (CONVECTION MODE) key. When
R-8R51(W}
R-8R51(B}
the ij: >, START key is touched, the following op-
eration occur:
1. The numbers of the digital readout start the count
down to zero.
2. The oven lamp, turntable motor, cooling fan motor
and convection motor are energized.
3. Relay RY3 is energized (if the cavity temperature is
lower than the selected temperature) and the mains
supply voltage is applied to the convection heating
element to return to the selected cooking temper-
ature.
4, Upon completion of the cooking time, the audible
signal will sound, and oven lamp, turntable motor,
cooling fan motor and convection motor, are
de-energized. At the end of the convection cycle,
if the thermistor temperature is above 178°C, the
circuit to RY-7 will be maintained (by the thermistor
circuit) to continue operation of the cooling fan
motor unit the temperature drops below 100°C, at
which time the relay will be de-energized, turning
off the fan motor. RelayRY-6 will however, opens
as soon as the convection cycle has ended, turning
off the convection motor.
5. At the end of the convection cook cycle, shut-off
relay RY-5 is energized turning on the damper
motor. The damper is returned to the open position,
closing the damper switch contacts which send a
signal to the control unit, de-energizing shut-off
relay RY-5.
GRILL COOKING CONDITION
(Figure 0-4)
In this condition the food is cooked by grill heating
element energy. And at the initial period (approxi-
mately 10 minutes) the convection heating element 1s
also activated.
Program desired cooking time and grill mode by
touching (1) (7) () (TIME) keys and (GRILL
MODE) key. >
When the [++ +) START key is touched, the following
operations occur: ;
1. The numbers of the digital readout start the count
down to zero.
. The damper motor ts turned on to close the damper.
. The relays RY1+RY6+RY7 are energized.
. The oven tamp, turntable motor, cooling fan motor,
and convection motor are energized.
. The relay RY4 is energized. The two (2) grijl heating
elements are energized. At the same time, if the
oven cavity temperature is lower than 215°C the
relays RY3 and RY6 are energized. And the con-
vection motor CM and the convection heating ele-
ment CH are energized once.
6. When the thermistor temperature reaches more than
215°C, the relay RY3 and RY6 are energized. And
the convection motor CM and the convection
heating element CH are de-energized. After that,
they are not be energized again.
7. Now, the food ts grilled by the grill heating element
(and convection heating element).
8. If the temperature of thermistor becomes more than
250°C, the grill heating element is stopped to be
heated. The temperature becomes Jess than 250°C,
the grill heating element is heated again. After
cooking, if the thermistor temperature is more than
100°C the circuit to RY7 will be ‘maintained (by
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