National NN-V680W, Service Manual

Page: 9 / 44

4.1. 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.
4.2. Grill cooking
The digital programmer circuit generates the power relay 4
control signal at ON time during grill cooking.*
4.3. Combination cooking
Combination cooking is accomplished by microwave and grill
cooking. The digital programmer circuit controls ON-OFF time
of power relay 1 and 4 as shown in the table.*
*NOTE: After grill and combination cooking, fan motor
rotates
for 7 minutes to cool oven and electric
components.
4.4. Auto Defrost Control
When those auto control feature is selected and Start pad is
pressed:
1. The digital programmer circuit determines the power level
and cooking time to complete cooking and indicates the
operating state in the display. The table shows the
corresponding cooking times for respective weight by
categories.
2. When cooking time in the display window has elapsed, the
oven turns off automatically by the controlled signal from
the digital programmer ciruit.
4 DESCRIPTION OF OPERATING SEQUENCE
9
NN-V690P / NN-V690PS / NN-V680W / NN-V680W