R-15AT
7
OPERATION SEQUENCE
OFF CONDITION
Closing the door activates the primary interlock relay
control switch SW1 and 2nd. interlock switch SW2 .
IMPORTANT:
When the oven door is closed, the contacts COM-NC
of the monitor switch SW3 must be open. When the
microwave oven is plugged in a wall outlet (230V
50Hz), the line voltage is supplied to the noise filter
and the control unit
Figure O-1 on page 30
1. The oven display will show . .
MICROWAVE COOKING CONDITION
Program desired cooking time by touching SELECT TIME
pad and the NUMBER pads. When the START pad is
touched, the following operations occur:
Figure O-2 on page 30
RELAY
CONNECTED COMPONENTS
RY-2
High voltage transformer
RY-3
Oven lamp/Antenna motor/Fan motor
1. The line voltage is supplied to the primary winding of
the high voltage transformer. The voltage is converted
to about 3.3 volts A.C. output on the filament winding
and high voltage of approximately 2300 volts A.C. on
the secondary winding.
2. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2000 volts) is
sent to the voltage doubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..
3. The 2450 MHz microwave energy produced in the
magnetron generates a wave length of 12.24 cm. This
energy is channelled through the waveguide (transport
channel) into the oven cavity, where the food is placed
to be cooked.
4. When the cooking time is up, a signal tone is heard and
the relays RY2 + RY3 go back to their home position.
The circuits to the oven lamp, high voltage transformer,
fan motor and antenna motor are cut off.
5. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch
Contact
Condition
During
Oven Door
Cooking
Open(No cooking)
primary interlock relay
control switch
COM-NO
Closed
Opened
2nd. interlock switch
COM-NO
Closed
Opened
Monitor Switch
COM-NC
Opened
Closed
The circuit to the high voltage transformer, fan motor and
antenna motor are cut off when the 2nd. interlock switch
SW2 is made open. The oven lamp remains on even if the
oven door is opened after the cooking cycle has been
interrupted, because the relay RY-3 stays closed. Shown
in the display is remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch SW3 is mechanically controlled by
the oven door, and monitors the operation of the 2nd.
interlock switch SW2.
6-1. When the oven door is opened during or after the
cycle of a cooking program, the 2nd. interlock switch
SW2 and primary interlock relay control switch SW1
must open their contacts first. After that the contacts
(COM-NC) of the monitor switch SW3 can be closed.
6-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switch SW3 must be opened. After
that the contacts of the 2nd. interlock switch SW2, and
primary interlock relay control switch SW1 are closed.
6-3. When the oven door is opened and the contacts of the
2nd. latch switch SW2 and the relay RY3 remain
closed, the fuse F10A will blow, because the monitor
switch SW3 is closed and a short circuit is caused.
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the line
voltage is supplied to the power transformer intermittently
through the contacts of relay (RY-2) which is operated by
the control unit within a 32 second time base. Microwave
power operation is as follows:
VARI-MODE
ON TIME
OFF TIME
Power 10(P-HI)
32 sec.
0 sec.
(100% power)
Power 9(P-90)
30 sec.
2 sec.
(approx. 90% power)
Power 8(P-80)
26 sec.
6 sec.
(approx. 80% power)
Power 7(P-70)
24 sec.
8 sec.
(approx. 70% power)
Power 6(P-60)
22 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)
12 sec.
20 sec.
(approx. 30% power)
Power 2(P-20)
8 sec.
24 sec.
(approx. 20% power)
Power 1(P-10)
6 sec.
26 sec.
(approx. 10% power)
Power 0(P-0)
0 sec.
32 sec.
(0% power)
Note:
The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approx. 2 seconds are needed for heating of the
magnetron filament.