7.1. Variable power cooking
control
High Voltage Inverter Power supply (U) controls output power
by the signal from Digital Programmer Circuit (DPC). Power
relay stays ON for P4 to P10 and For P1 to P3, both inverter
drive signal and power relay to control output power.
NOTE:
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.
Variable Power Cooking
OUTPUT ON-OFF TIME OF
POWERSETTING POWER(%) POWER RELAY B (RY1)
APPROX. ON(SEC) OFF(SEC)
HIGH P10 100% 22 0
P9 90% 22 0
P8 80% 22 0
MEDIUM-HIGH P7 70% 22 0
MEDIUM P6 60% 22 0
P5 50% 22 0
P4 40% 22 0
MEDIUM-LOW P3 30% 17 5
P2 20% 11 11
P1 10% 6 16
DEFROST P3 30% 17 5
7.2. Inverter power supply circuit
NEW H.V.
This Inverter Power Supply Circuit supplies 4,000V DC to the
magnetron tube from the line voltage, 120V 60Hz AC input.
functions as the H.V. transformer, the H.V.capacitor and
H.V.Diode.
1. The AC input voLtage 120V 60Hz is rectified to DC voltage
immediately.
2. 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.
3. This drives the High voltage transformer to increase up to
2,000V AC and approximately 3V AC by means of
transformer.
4. Then the half-wave doubler voltage rectifier circuit,
consisting of the H.V. diodes and Capacitors, generates the
necessary 4,000V DC needed for the magnetron.
5. Output power of the magnetron tube is always monitored by
the signal output from the current transformer built into the
inverter ciruit.
6. 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.
7.3. Inverter turbo defrost
When this Auto Control feature is selected and the Start Pad is
tapped:
1. 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.
2. When cooking time the display window has elapsed, the
oven tums off automatically by a control signal from the
digital programmer circuit.
Inverter Turbo Defrost
WEIGHT SELECTED COOKING TIME
1.0LB 5 min.28 sec.
7 DESCRIPTION OF OPERATING SEQUENCE
11
NN-S262SF / NN-S262BF / NN-S262WF / NN-S252BF / NN-S252WF
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