Sharp R-21JCA-F Operation, Description of Operating Sequence, OFF Condition, Cooking Condition

R-21JCA-F

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

The following is a description of component functions during oven operation.

OFF CONDITION

Closing the door activates door sensing 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 noise filter and the control unit (Figure O-1).

COOKING CONDITION

When the Light Up Dial is turned, 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	CONNECTED COMPONENTS
RY-1	Oven lamp/ Antenna motor/ Fan motor
RY-2	Power transformer

2.120 volts A.C. is supplied to the primary winding of the power transformer and is converted to about 3.2 volts A.C. output on the filament winding, and approximately 2150 volts A.C. on the high voltage winding.

3.The filament winding voltage heats the magnetron filament and the H.V. winding voltage is sent to a voltage doubler circuit.

4.The microwave energy produced by the magnetron is channelled through the waveguide into the cavity feed-box, and then into the cavity where the food is placed to be cooked.

5.Upon completion of the cooking time, the power transformer, 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, monitor switch, door sensing switch, secondary interlock switch, relay (RY2) and primary interlock relay(RY1) are activated with the following results. The circuits to the antenna motor, the cooling fan motor, the oven lamp and the high voltage components are de-energized, and the cooking program will be canceled when the door was opened.

7.The monitor switch electrically monitors the operation of the secondary interlock switch and primary interlock relay(RY1) and is mechanically associated with the door so that it will

function in the following sequence.

(1)When the door opens from the closed position, the primary interlock relay(RY1) and secondary interlock switch open their contacts. Then the monitor switch contacts close.

(2)When the door is closed from the open position, the monitor switch contacts open first. Then the contacts of the secondary interlock switch and door sensing switch close.

If the secondary interlock switch and primary interlock relay (RY1) fail with the 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, and primary interlock relay(RY1), causing the monitor fuse to blow.

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