TECHNICAL TERMS
Domestic appliances. They are appliances like microwave oven, blender, washing machine, flat iron, etc.
Resistance heating appliance. It is an appliance that uses resistive load for its main part which produces heat when current passes through it.
Thermostat. It is a type of switching system that is being controlled by temperature.
Heating element. It is a part of a resistance heating appliance that gets hot when operated.
Electrical components. They are devices that perform electrical activities when current is applied to the circuit.
Mica insulator. It is a transparent material that splits readily into thin sheets which have excellent insulating and heat resisting qualities. Non - electrical components. They are parts of an appliance that performs
designated function other than electrical application.
ON / Off switch. It is used to designate the operating and the inoperative state of a device or unit.
Timer. It is a device that opens the electrical circuit after a predetermined period of time elapses.
Thermistor. It is a device with high negative temperature coefficient or resistance, so its resistance decreases as temperature rises.
Power. It is the rate at which electric energy is fed to or taken from a device measured in watts.
Watt. It is the basic unit of power which in one second gives rise to energy of one joule.
Fluro pan. It is an aluminum pan that is used to store food stuff like rice, corn, etc.
Troubleshooting. It is a problem solving process with the goal of returning an item to its operational state.
4 Program/Course: CONSUMER ELECTRONIC SERVICING NC II
Unit of Competency: MAINTAIN AND REPAIR ELECTRONICALLY CONTROLLED DOMESTIC APPLIANCES
Module Title: MAINTAINING AND REPAIRING A MICROWAVE OVEN
Learning Outcome 1:
Identify the parts and functions of a microwave oven.Assessment Criteria
1. The operation of microwave oven is explained. 2. The parts of a microwave oven are identified. 3. The functions of its parts are discussed.
References:
1. Tan, Michael Q., Gantalao, Fred T., Lasala, Rommel M. Simple Electronics; Andes Mountain Printers: 2004
2. Enriquez, Marcelo T. Electronics Technology IV; Souvenir Publications, Inc.: 2003
5
LEARNING EXPERIENCES/ACTIVITIES
Learning Outcome 1:
Identify the parts and functions of a microwave oven.Learning Activities Special Instruction 1. Read the attached Information
Sheet 1.1 on microwave oven. 2. Answer the Self Check 1.1. 3. Compare your answer with the
model answer. Self-Check key1.1.
4. If you missed some of the questions, go back again to Information Sheet 1.1.
5. If you have answered the questions, you are ready to proceed to learning outcome 2.
Try to answer the Self-Check 1.1 without looking at the
6
INFORMATION SHEET 1.1
Operation of Microwave Oven
Microwave oven
Is a kitchen appliance that can come in many different sizes and styles employing microwave radiation primarily to cook or to heat food. This is made possible by using microwaves emitted from a magnetron to excite water (primarily) and other polarized molecules within the food to be heated.
How the microwave operates?
Microwave ovens are generally used for time efficiency in both industrial applications such as restaurants and at home, rather than for cooking quality, although some modern recipes using microwave ovens rival recipes using traditional ovens and stoves. They have a central heated anode which is the source of electrons. These are several identical tuned cavities a very strong magnet, and a small antenna to extract the energy. They are usually made of metal but operate on the same principles that glass thermionic valves do.
7 Major Parts and its Functions
Magnetron
The magnetron is a device for producing microwave radiation from electricity. A variation on this device, called the cavity magnetron is usually used as the microwave energy source in your microwave oven. It can also be used as the microwave source in a pulsed radar.
High voltage transformer
It is the "muscle" of the microwave oven. With an input of 120 VAC (or 240 VAC in many commercial models) applied to the primary winding, the high-voltage transformer (also referred to as power or plate transformer) steps up that primary voltage to a very high voltage. This high voltage is then boosted even higher by the voltage-doubling action of the capacitor and diode.
Varistor
It is a type of resistor with a significantly non-ohmic current-voltage characteristic. The name is a portmanteau of variable resistor which is misleading since it is not continuously user-variable like a potentiometer or rheostat, and is not a resistor but in fact a capacitor. Varistor is often used to protect circuits against excessive voltage by arching.
Fuse
It is a wire, bar, or strip of fusible metal inserted for safety in an electric circuit. When the current increases beyond a certain safe strength, the metal melts, interrupting the circuit and thereby preventing possibility of damage.
8 High voltage diode
It is a high voltage diode has a lamellar structured body of semiconductor material. The lamellar structure is produced by the thermal gradient zone melting process method of migrating metal "wires" through the body to form a plurality of spaced regions of conductivity opposite to that of the body.
Latch switch
It is a switch having a bimetal latch for locking a resilient contact in a closed circuit position and a heating coil for activation of the latch to release the contact.
Oven lamp
9 SELF-CHECK 1.1
Direction: Label the parts of the microwave oven based from the given Description. Write your answer in another sheet of paper.