This unit involves the skills and knowledge required to develop engineering solutions for direct current (d.c.) machine and control problems.

It includes working safely; determining problem; obtaining direct current d.c. machine operation, construction and application; gathering and analysing data; applying problem-solving techniques; and developing and documenting solutions.

The skills and knowledge described in this unit require a licence or permit to practice in the workplace where work is carried out on electrical installations which are designed to operate at voltages greater than 50 volt (V) alternating current (a.c.) or 120 V d.c..

Competency development activities in this unit are subject to regulations directly related to licensing. Where a licence or permit to practice is not held, a relevant contract of training, such as an Australian Apprenticeship, may be required.

Additional and/or other conditions may apply in some jurisdictions subject to regulations related to electrical work. Practice in the workplace and during training is also subject to work health and safety (WHS)/occupational health and safety (OHS) regulations.

Permits may also be required for some work environments such as confined spaces, working aloft, near live electrical apparatus and site rehabilitation

ELEMENTS

PERFORMANCE CRITERIA

Elements describe the essential outcomes.

Performance criteria describe the performance needed to demonstrate achievement of the element.

1

Prepare to develop engineering solution for d.c. machine problems

1.1

WHS/OHS processes and workplace procedures for a given work area are identified, obtained and applied

1.2

WHS/OHS risk control measures and workplace procedures in preparation for the work are followed

1.3

Scope of d.c. machine problem is determined from performance specifications and/or documentation and in consultation with relevant person/s

1.4

Activities are planned to meet scheduled timelines in consultation with others involved in the work

1.5

Strategies are formed to ensure solution development and implementation is carried out efficiently

2

Develop engineering solution for d.c. machine problems

2.1

WHS/OHS risk control measures and workplace procedures for carrying out the work are followed

2.2

Relevant d.c. machine construction operation characteristics and applications are applied to developing solutions to d.c. machine problems

2.3

Parameters, specifications and performance requirements to each machine problem are obtained in accordance with workplace procedures

2.4

Approaches to resolving d.c. machine problems are analysed to provide most effective solutions

2.5

Unplanned events are dealt with safely in accordance with relevant industry standards and workplace procedures

2.6

Quality of work is monitored in accordance with relevant industry standards and workplace procedures

3

Implement engineering solution and complete documentation

3.1

Solutions to machine problems are tested to determine their effectiveness and modified as required

3.2

Adopted solutions are documented and instructions for implementation with risk control measure developed

3.3

Relevant person/s required to implement solutions to d.c. machine problems is coordinated in accordance with relevant industry standards and workplace procedures

3.4

Justification for solutions used to solve d.c. machine problems is documented in work/project records in accordance with relevant industry standards

Evidence required to demonstrate competence in this unit must be relevant to and satisfy all of the requirements of the elements, performance criteria and range of conditions on at least one occasion and include:

understanding the extent of the machine problem

forming effective strategies for solution development and implementation

obtaining machine parameters, specifications and performance requirements appropriate to each problem

testing and solutions to machine problems

documenting instruction for implementation of solutions that incorporate risk control measure to be followed

documenting justification of solutions implemented in accordance with professional standards

dealing with unplanned events

applying relevant work health and safety (WHS)/occupational health and safety (OHS) requirements, including using risk control measures

determining the scope of direct current (d.c.) machine problems

planning activities to meet timelines

analysing approaches to solutions

monitoring quality of work.

Evidence required to demonstrate competence in this unit must be relevant to and satisfy all of the requirements of the elements, performance criteria and range of conditions and include knowledge of:

d.c. machine diagnostics and engineering solutions for d.c. machine problems, including:

basic d.c. machine construction and operation encompassing:

general principles of operation

applications of d.c. machines

construction of d.c. machines

d.c. machine configurations; series, shunt, compound long shunt and compound short shunt

armature and field currents

insulation

ratings

cooling paths

bearings

general maintenance of d.c. machines

construction and use of lap and wave windings encompassing:

coils and elements

generated voltage equation for generator

generated voltage equation for motors

application of lap and wave windings

commutation process encompassing:

use of interpoles

loading of machines

brush shifting

brush selection

classes of brush grades:

natural graphite, hard carbon, electrographite, metal-graphite and metal-carbon, "treated" grades

carbon brush contact characteristics:

specific resistance, thermal conductivity, density and porosity, elastic properties and contact properties

carbon brush factors:

pressure, current, polarity and speed

brush construction:

dimensions, tolerances, preferred sizes, surfaces, edges, bevels, flexible shunts, connection of flexible shunt to brush and insulation of flexible connections

brush holders:

types, brush angles, trailing holders, reaction holders, top bevel angles, reversible rotation, cantilever holders, effective arc of contact, construction of brush holders and pressure mechanism

mounting of brush holders and brushes:

clearances, brush angle, brush arm spacing, alignment, staggering, brush bedding and brush pressure

brush operation:

temperature rise, number and size of brushes, current distribution between brushes, slotting brushes, polarity effects, arc of contact, materials for commutators and mica

selection of brush grades:

machine data, current density, commutator peripheral speed, brush arc, pitch of segments, number of segments covered by brush and cooling surface

armature reaction in d.c. machines encompassing:

effect of armature reaction on d.c. machine characteristics

use of compensating winding

d.c. generators encompassing:

relative advantages and disadvantages of the various d.c. generator configurations and their performance under various load conditions

voltage regulation as a percentage or per unit value

operation in parallel

d.c. motors encompassing:

relative advantages and disadvantages of the various d.c. motor configurations and their performance under various load conditions

shape of motor speed/torque curves

reversal of rotation

starting and protection of d.c. motors encompassing:

types of d.c. motor starters in use

d.c. motor protection

speed regulation and speed control of d.c. motors encompassing:

methods in use

effect on motor design and operation caused by the use of SCR

speed control equipment

braking of d.c. motors encompassing:

plugging

dynamic

regenerative

mechanical

losses, heating and efficiency encompassing:

copper losses

iron losses

mechanical losses

efficiency

acceleration of d.c. motors and loads encompassing:

characteristics of typical loads

matching a suitable motor to a given load

heating of windings

derating of motors

special d.c. motors construction, operation and applications encompassing:

permanent-magnet motors

brushless motors (e.c. motors)

coreless and moving coil motors

linear motors

printed circuit motor

stepping motors

voice-coil motors

maintenance of d.c. machines encompassing:

routine maintenance

breakdown repairs

types of faults encompassing:

brushes/brush gear problems:

sparking, excessive heating, excessive wear of brushes, commutator or slip rings, bad surface conditions, excessive maintenance, flexible burning, flexible corrosion, separation or grooving, blackening, copper picking, copper dragging and brush noise

adjustment of machines encompassing:

correct brush position

machining and finishing of commutators

problem-solving techniques

machine parameters, specifications and performance requirements

relevant manufacturer specifications and operating instructions

relevant job safety assessments or risk mitigation processes

relevant WHS/OHS legislated requirements

relevant workplace documentation

relevant workplace quality, instructions, policies and procedures.

Assessors must hold credentials specified within the Standards for Registered Training Organisations current at the time of assessment.

Assessment must satisfy the Principles of Assessment and Rules of Evidence and all regulatory requirements included within the Standards for Registered Training Organisations current at the time of assessment.

Assessment must occur in suitable workplace operational situations where it is appropriate to do so; where this is not appropriate, assessment must occur in simulated suitable workplace operational situations that replicate workplace conditions.

Assessment processes and techniques must be appropriate to the language, literacy and numeracy requirements of the work being performed and the needs of the candidate.

Resources for assessment must include access to:

a range of relevant exercises, case studies and/or simulations

relevant and appropriate materials, tools, facilities and equipment currently used in industry

resources that reflect current industry practices in relation to developing engineering solutions for d.c. machine problems

applicable documentation, including workplace procedures, equipment specifications, regulations, codes of practice and operation manuals.

Foundation skills essential to performance are explicit in the performance criteria of this unit of competency.

Range is restricted to essential operating conditions and any other variables essential to the work environment.

Non-essential conditions may be found in the UEE Electrotechnology Training Package Companion Volume Implementation Guide.

Developing engineering solutions must include the following:

at least two different d.c. machines using different control systems

Electrotechnology

Electrical