National NN-C781JF, Руководство по обслуживанию

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DESCRIPTION OF OPERATING SEQUENCE
1. Variable power cooking control
HIGH-VOLTAGE INVERTER POWER SUPPLY (U) controls output
power by the signal from Digital Programmer Circuit (DPC). Power relay
1 stays on but the inverter drive signal to control it’s output power.
NOTE 1: The ON/OFF time ratio does not correspond with the
percentage of microwave power since approximately 2
seconds are required for heating of magnetron filament.
NOTE 2: If microwave cooking is over 3 minutes, fan motor rotates for
1 minute after cooking to cool oven and electric components.
2. Inverter Power Supply Circuit NEW H.V.
This Inverter Power Supply Circuit supplies 4,000V DC to the magnetron
tube from the line voltage, 220-240V 50Hz / 120V 60Hz AC input. functions
as the H.V. transformer, the H.V.capacitor and H.V.Diode.
(A) The AC input voLtage 220-240V 50Hz / 120V 60Hz is rectified to DC
voltage immediately.
(B) DC voltage will be supplied to the switching devices called IGBT.
These devices will be switched ON-OFF by the 20 to 40 kHz PWM.
(pulse width modulation) signal from the microcomputer in the DPC.
(C) This drives the High voltage transformer to increase up to 2,000V
AC and approximately 3V AC by means of transformer.
(D) Then the half-wave doubler voltage rectifier circuit, consisting of the
HV diodes and Capacitors, generates the necessary 4,000V DC
needed for the magnetron.
(E) Output power of the magnetron tube is always monitored by the
signal output from the current transformer built into the inverter
ciruit.
(F) Then this signal will be fed back to the microcomputer in the DPC to
determine operating conditions and output necessary to control PWM
signal to the inverter Power Supply to control output power.
3. Turbo Defrost Control
When this Auto Control feature is selected and the Start Pad is tapped:
(A) The digital programer circuit determines the power level and
cooking time to complete cooking and indicates the operating state
in the display window. Table shows the corresponding cooking
times for respective serving by categories.
(B) When cooking time the display window has elapsed, the oven
tums off automatically by a control signal from the digital
programmer circuit.
4. Convection Cooking Control
The digital programmer circuit controls the ON-OFF time of the heater
in order to control oven cavity temperature.
(A) After the start pad is tapped with the desired Bake/Broil program
set, an 12V DC singal comes out of the digital programmer circuit
and is applied to coil of power relay (RY4).
(B) When the contacts of power relay 4 close, power source voltage
is applied to the heater and the heater turns on.
(C) When the oven temperature reaches the set temperature, the
digital programmer circuit senses the temperature through oven
temp sensor and stops supplying and 12V DC signal to the coil of
power relay 4 and the heater turns off.
(D) After the heater turns off, the oven temperature will continue
increasing a while and then decrease as shown in Figure. When
the oven temperature drops below the set temperature, the digital
programmer circuit senses the signal and starts supplying an 12C
DC signal to the coil of power relay again.
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POWER SETTING
OUTPUT
POWER(%)
APPROX.
Variable Power Cooking
HIGH
MEDIUM-HIGH
MEDIUM
MEDIUM-LOW
LOW
DEFROST
100%
70%
55%
30%
10%
30%
stay ON
stay ON
stay ON
15s ON / 7s OFF
8s ON / 14s OFF
16s ON / 6s OFF
stay ON
stay ON
stay ON
ON / OFF
ON / OFF
ON / OFF
INVERTER
CONTROL
SIGNAL
RY-1
OVEN TEMP
HEATER
(RY4)
CONVECTION
FAN MOTOR
(RY5)
OVEN TEMP
SELECTED OVEN TEMP
START
ON OFF ON OFF ON
ON
Turbo Defrost
WEIGHT
SELECTED
1.0KG
COOKING TIME
14min. 36 sec.
Convection Cooking