Panasonic NN-H264SFR Service Manual

Also see for Inverter NN-H275: Operating instructions Operating instructions Service manual

The ON/OFF time ratio does not correspond with the percentage of microwave power sinceapproximately 2 seconds are required for heating of magnetron filament.Variable Power CookingOUTPUT ON-OFF TIME OFPOWERSETTING POWER(%)POWER RELAY B(RY1)APPROX. ON(SEC) OFF(SEC)HIGHP10100% 22 0P9 90% 22 0P8 80% 22 0MEDIUM-HIGHP7 70% 22 0MEDIUM P6 60% 22 0P5 50% 22 0P4 40% 22 0MEDIUM-LOWP3 30% 17 5P2 20% 11 11P1 10% 6 16DEFROST P3 30% 17 57.2. 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 ACand approximately 3V AC by means of transformer.4. Then the half-wave doubler voltage rectifier circuit, consisting of theH.V. diodes and Capacitors, generates the necessary 4,000V DCneeded for the magnetron.5. Output power of the magnetron tube is always monitored by the signaloutput from the current transformer built into the inverter ciruit.6. Then this signal will be fed back to the microcomputer in the DPC todetermine operating conditions and output necessary to control PWMsignal to the Inverter Power Supply to control output power.7.3. Inverter turbo defrost15