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22765 Demonstrate knowledge of microwave ovens for electrical

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22765 Demonstrate knowledge of microwave ovens for electrical

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    Demonstrate knowledge of microwave ovens for electrical appliance service technicians

Level 4

    Credits 4

    Purpose This unit standard covers basic principles, operation, safety requirements

    and maintenance and repair of microwave ovens. It is intended for use in the

    training of electrical appliance servicing technicians.

     People credited with this unit standard are able to:

     provide an overview of microwave cooking and ovens;

     demonstrate knowledge of the operating principles of microwave ovens;

     demonstrate knowledge of the safety requirements when servicing

    microwave ovens;

     demonstrate knowledge of the component tests, failures and corrective

    actions; and

     demonstrate knowledge of newer or alternate technologies being used

    for microwave cooking.

Subfield Electrical Engineering

    Domain Electrical Appliance Servicing

    Status Registered

    Status date 20 June 2006

    Date version published 20 June 2006

    Planned review date 31 December 2011

    Entry information Open.

    Accreditation Evaluation of documentation and visit by NZQA and

    industry.

    Standard setting body (SSB) ElectroTechnology Industry Training Organisation

    Accreditation and Moderation Action Plan (AMAP) reference 0003

    This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.

Special notes

    1 This unit standard has been designed for learning and assessment off-job.

     ; New Zealand Qualifications Authority 2012

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    2 References

     Consumer Guarantees Act 1993;

     Electricity Act 1992, Electricity Regulations 1997, and relevant New Zealand

    Electrical Codes of Practice and Standards;

     Fair Trading Act 1986;

     Health and Safety in Employment Act 1992;

     AS/NZS 60335.2.25:2002, Household and similar electrical appliances safety. Part

    2.25, Particular requirements for microwave ovens, including combination microwave

    ovens;

     and their subsequent amendments and replacements.

3 Range

     The range and depth of subject knowledge is such as to facilitate competent and safe

    electrical servicing of microwave ovens.

Elements and performance criteria

Element 1

Provide an overview of microwave cooking and ovens.

Performance criteria

    1.1 The basic principles of microwave energy are described with reference to

    ionizing and non-ionizing radiation, and frequency.

    1.2 The process by which food is cooked by microwaves is described.

    Range microwave penetration, proportional relationships, microwaves

    and metal.

    1.3 Safety considerations when cooking or using microwave ovens are described.

    Range arcing and back-feed, measurement of microwaves, safe levels of

    exposure, safety distances, pacemakers, radiation injuries, colour

    television emissions.

Element 2

    Demonstrate knowledge of the operating principles of microwave ovens.

Performance criteria

    2.1 The operation of the high-voltage system of a typical microwave oven is

    described with the aid of sketches.

    Range magnetron tube effect of the magnetic field, resonant circuit,

    waveguide, Radio Frequency (RF) capacitors, cooling fins,

    phasing, life expectancy;

     transformers high voltage transformer, filament transformer;

     high voltage circuit high voltage capacitor and diode, half-wave

    voltage doubler, full-wave voltage doubler.

     ; New Zealand Qualifications Authority 2012

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    2.2 The operation of the control systems of a typical microwave oven is described

    with reference to the primary circuit, subcircuits, components, and modules, and

    with the aid of sketches.

    Range timers pushbutton, electronic, glass touch panels, membrane

    switch panels;

     typical electronic control systems generalised control panel

    circuit, control transformer, cook relay;

     processes start up, holding and shutdown operation; start up,

    idle and cooking operation;

     secondary and subsidiary control, and components output power

    control, primary side duty control (mechanical and solid state);

    triac drive circuit and system operation; secondary side duty

    control including varying of high-voltage potential, phase control,

    probe, humidity sensor, infrared sensor, convection cooking

    control.

    2.3 The essential safety and protection circuits are described.

    Range interlocking switches and circuits, monitor switch, sequencing;

     protection devices thermal, voltage (varistor, surge absorber,

    Positive Temperature Coefficient resistor), fuses, magnetron

    protection and failure detection.

    2.4 Microwave containment, cooling and energy dispersion systems are described.

    Range containment cooking cavity, cooking shelf, waveguide, door

    leakage safety;

     cooling and energy dispersion cooling, stirrer, food rotation,

    energy dispersal, turntable, rotating antenna, stirrer and

    waveguide covers, baffles.

Element 3

    Demonstrate knowledge of the safety requirements when servicing microwave ovens.

Performance criteria

    3.1 The principles, procedures and use of instruments relating to testing for

    electrical safety are summarised with regard to the supply.

    Range test before touch, prove-test-prove, practices and limitations

    relating to the use of test instruments, checks to ensure isolation,

    means of ensuring that isolation is maintained.

    3.2 The dangers of working with high voltage circuits are described, and means of

    ensuring safety are identified.

    3.3 The possibility of RF exposure is identified, and preventative measures

    described.

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    Element 4

    Demonstrate knowledge of the component tests, failures and corrective actions.

Performance criteria

    4.1 High voltage components tests are identified and described with reference to

    failure identification.

    Range isolation test, power output check, magnetron plate current test,

    filament transformer voltage test, high voltage transformer test,

    high voltage capacitor test, diode check, half-wave rectifier test.

    4.2 Control component and circuit tests are identified and described with reference

    to failure identification.

    Range electromechanical, pushbutton and solid state timer checks and

    tests; low voltage transformer and transformer tests; warm-up

    delay and time delay circuit tests and checks, start-up, holding and

    shutdown relay tests; output power control testing; solid state

    controller, devices, modules and Triac tests and checks;

    temperature control probe testing; infrared sensor check;

    thermistor test.

    4.3 Safety and protection circuit tests are identified and described with reference to

    failure identification.

    Range door interlocks checks and adjustments, solenoid latch test,

    thermal protection tests, ferrite isolator test, surge monitor system

    check, voltage protection device tests, supply and supply fuses

    tests.

    4.4 Containment, cooling and energy dispersion checks are identified and

    described with reference to failure identification.

    Range choke cavity clean, cooking cavity clear of rust, corrosion damage

    to metal or painted surfaces, waveguide disorders, door leakage

    and safety, adjustment on door correct, blower motor test,

    microwave heat distribution test, stirrer or antenna rotation verified,

    stirrer and waveguide covers in place and complete, grease and

    spatter shield clean and in place.

Element 5

    Demonstrate knowledge of newer or alternate technologies being used for microwave cooking.

Performance criteria

    5.1 The additional requirements needed for the convection option in a microwave

    oven are described.

     ; New Zealand Qualifications Authority 2012

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    Range heating elements, power circuits, control circuits, structural or

    mechanical requirements.

    5.2 A brief overview of new technology in relation to bench top cooking is provided.

    Range inverter technology, cooking with light (halogen light source

    converted to microwave), magnetic induction as an alternative,

    touch screen control built into microwave oven doors including

    internet ready connection.

Please note

    Providers must be accredited by the Qualifications Authority, or an inter-institutional body with delegated authority for quality assurance, before they can report credits from assessment against unit standards or deliver courses of study leading to that assessment.

    Industry Training Organisations must be accredited by the Qualifications Authority before they can register credits from assessment against unit standards.

    Accredited providers and Industry Training Organisations assessing against unit standards must engage with the moderation system that applies to those standards.

    Accreditation requirements and an outline of the moderation system that applies to this standard are outlined in the Accreditation and Moderation Action Plan (AMAP). The AMAP also includes useful information about special requirements for organisations wishing to develop education and training programmes, such as minimum qualifications for tutors and assessors, and special resource requirements.

Comments on this unit standard

     Please contact the ElectroTechnology Industry Training Organisation

    reviewcomments@etito.co.nz if you wish to suggest changes to the content of this unit standard.

     ; New Zealand Qualifications Authority 2012

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