Electrolux EI30MH55GB Service Manual - Page 9

OPERATION EI30MH55GSA EI30MH55GBA EI30MH55GWA DESCRIPTION OF OPERATING SEQUENCE The following is a description of component functions during oven operation. OFF CONDITION Closing the door activates the stop switch, primary interlock switch and secondary interlock switch. (In this condition, the monitor switch contacts are opened.) When oven is plugged in, 120 volts A.C. is supplied to the control unit. (Figure O-1). 1. The display will show flashing "88 : 88". To set any program or set the clock, you must first touch the STOP/CLEAR button. The display will clear, and " : " will appear . COOKING CONDITION Program desired cooking time touching the NUMBER pads. When the START button is touched, the following operations occur: 1. The contacts of relays are closed and components connected to the relays are turned on as follows. (For details, refer to Figure O-2) RELAY RY1 RY3, RY4 CONNECTED COMPONENTS Oven lamp / Fan motor / Stirrer motor Hood fan motor 2. 120 volts A.C. is supplied to the inverter unit and is converted in order to power of the magnetron by the high frequency switching power circuit. The frequency is approx. 33 _ 45 KHz. 3. The filament winding voltage of H.V. transformer heats the magnetron filament and the H.V. winding gives a high voltage approx. 2 KV to activaite a voltage doubler circuit.Then approx. 4KV peak voltage power is supplied to the magnetron cathode terminal. 4. The microwave energy produced by the magnetron is channelled through the waveguide into the cavity feedbox, and then into the cavity where the food is placed to be cooked. 5. Upon completion of the cooking time, the inverter unit, oven lamp, etc. are turned off, and the generation of microwave energy is stopped.The oven will revert to the OFF condition. 6. When the door is opened during a cook cycle, the monitor switch, stop switch, secondary interlock switch and primary interlock switch are activated with the following results. The circuits to the stirrer motor, the cooling fan motor, the turntable motor, and the inverter unit are de-energized, and the touch screen displays the time still remaining in the cook cycle when the door was opened. 7. The monitor switch is electrically monitoring the operation of the secondary interlock switch and primary interlock switch and is mechanically associated with the door so that it will function in the following sequence. (1) When the door opens from a closed position, the primary interlock switch and secondary interlock switch open their contacts, and then the monitor switch contacts close. And contacts of the relay (RY1) remain closed. (2) When the door is closed from the open position, the monitor switch contacts first open and the stop switch contacts open, and then the contacts of the secondary interlock switch and primary interlock switch close. And contacts of the relay (RY1) open. If the secondary interlock switch and primary interlock switch fail with their contacts closed when the door is opened, the closing of the monitor switch contacts will form a short circuit through the monitor fuse, secondary interlock switch, primary interlock switch and relay (RY1) causing the monitor fuse to blow. Variable COOKING When Variable Cooking Power is programmed, the 120 volts A.C. is supplied to the inverter unit which is operated by the control unit. Microwave power operation is as follows: The oven can be set for any of 11 power levels: 0% to 100%(HIGH). The variable cooking power less than 40% is programmed at the ratio of ON time and OFF time within 32 sec./ cycle time base. Connection between power setting and ON/ OFF time of inverter unit. OUTPUT POWER SETTING Power 100% Power 90% Power 80% Power 70% Power 60% Power 50% Power 40% Power 30% Power 20% Power 10% Power 0% ON TIME OFF TIME Continue operation 26 sec. 22 sec. 16 sec. 8 sec. 0 sec. 6 sec. 10 sec. 16 sec. 24 sec. 32 sec. Note: The ON/OFF time ratio does not correspond with the percentage of microwave power, because approx. 3 seconds are needed for heating of the magnetron filament. SENSOR COOKING CONDITION Using the Sensor cooking function the food is cooked without figuring time, power level or quantity. When the oven senses enough steam from the food, it relays the information to its microprocessor which will calculate the remaining cooking time and power level needed for best results. When the food is cooked, water vapor is developed. The sensor "senses" the vapor and its resistance increases gradually. When the