Description Of Operating Sequence - Panasonic NN-P994 Service Manual

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Operating instructions manual (60 pages)

Operating instructions manual (64 pages)

Table of Contents

1. Variable power cooking control

The coil of power relay B (RY1) is energized intermittently by the digital

programmer circuit, when the oven is set at any power selection except

for High power position. The digital programmer circuit controls the

ON-OFF time of power relay B contacts in order to vary the output

power of the microwave oven from "Low" to "High" power. One

complete ON and OFF cycle of power relay B is 22 seconds. The

relation between indications on the control panel and the output of the

microwave oven is as shown in table.

NOTE: The ON/OFF time ratio does not correspond with the

percentage of microwave power since approximately 2 sec-

onds are required for heating of magnetron filament.

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

HV 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.

3. Inverter Turbo Defrost

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.