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Elements and Performance Criteria

  1. Determine job requirements
  2. Prepare to fault-find on AC machines and associated control circuits
  3. Fault-find AC machines and associated control circuits
  4. Prepare to fault find on AC machines and associated control circuits
  5. Fault find AC machines and associated control circuits

Range Statement

This field allows for different work environments and conditions that may affect performance. Essential operating conditions that may be present (depending on the work situation, needs of the candidate, accessibility of the item, and local industry and regional contexts) are included.

AC machines include three (3) or more of the following:

single-phase motors

three-phase motors

variable speed drives (VFDs)

synchronous machines

non-rotating AC equipment and components

Control starter circuits include one (1) or more of the following:

direct-on-line (DOL)

star-delta

autotransformer

primary resistance

secondary resistance

Split phase induction motors include:

split-phase motor

capacitor-start motor

capacitor-start, capacitor-run motor

permanently-split capacitor motor

shaded-pole motor

Environmental protection and general enclosure types include:

open motors

protected motors

drip-proof motors

duct ventilated

totally enclosed

flameproof

Specialised test equipment includes one or more of the following:

built-in systems (software and site displays)

vibration monitors

infra-red temperature sensing device

Rotating electrical machines in general requirements include:

AS 1359.106-1996 Rotating electrical machines – General requirements – Methods of cooling (IC Code)

Regulatory requirements include:

AS/NZS 3000:2007 Electrical installations (known as the Australian/New Zealand Wiring Rules

Safe working practices include:

Ddmonstration of safe working practices and installation in accordance with industry established safe and sound practices

Performance Evidence

Evidence required to demonstrate competence in this unit must be relevant to and satisfy the requirements of the elements and performance criteria on at least two (2) occasions and include:

following work instructions, standard operating procedures (SOPs) and safe work practices

identifying and interpreting circuits, drawings and specifications relevant to the work to be undertaken

determining the electrical and non-electrical isolation requirements to prevent the creation of hazards linked from the loss of machine/system/process control according to established procedures

using lock out tag procedures with appropriate tags/signs

proving electrical isolation and following established safety rules prior to working on electrical equipment or wiring

ensuring all electrical equipment and tools are tested and tagged and up to date

using specialised test equipment, including condition monitoring equipment to conduct on-line analysis

carrying out on-line functional tests for voltage and current using a voltmeter or multimeter and a clip on ammeter

applying fault finding and diagnostic techniques on at least three (3) or more of the following AC machines and circuits:

single-phase motors

three-phase motors

variable speed drives (VSDs)

synchronous machines

non-rotating AC equipment and components

carrying out electrical tests for continuity and insulation resistance tests; between windings and to earth of single and three-phase motors

dismantling, replacing and assembling single and three-phase AC machines using appropriate hand and power tools in accordance with manufacturer specifications, if required

complying with the Australian/New Zealand Wiring Rules and local supply requirements for three-phase motor installations and starters

using a synchroscope for paralleling of alternators

documenting all necessary repairs in accordance with SOPs.

Knowledge Evidence

Evidence required to demonstrate the required knowledge for this unit must be relevant to and satisfy the requirements of the elements and performance criteria and include knowledge of:

safe work practices and procedures and use of personal protective equipment (PPE)

three-phase induction motors, including:

basic component parts of a three-phase induction motor, i.e. stator and rotor (squirrel-cage and wound rotor)

motor enclosures

terminal block arrangements – connecting a three-phase motor in both star and delta

operating principles, including:

rotating magnetic fields

rate of rotation and factors affecting it

direction of rotation and reversal

induction and its effects, including:

torque

slip

rotor frequency

operating characteristics ,including:

squirrel-cage rotors

special purpose squirrel-cage rotors

wound-rotor motors

operating parameters for induction motors

single-phase induction motors, characteristics and operating principles of the following:

split-phase motor

capacitor-start motor

capacitor-start, capacitor-run motor

permanently-split capacitor motor

shaded-pole motor

series motor – operating characteristics and reversing the direction of rotation

comparison of single-phase and three-phase motors and advantages and disadvantages of three-phase motors

abnormal operating conditions for three-phase motors, including:

phase reversal, single phasing and overloading

voltage fluctuation, higher operating temperatures, frequency variation, overloading and frequent starting

other factors, including exposure to corrosive fumes, explosive vapours, dust, steam, salt air, high humidity, operation in ambient temperature of below approximately 100C or above 400C, or operation at altitudes in excess of 1000 metres

abnormal operating conditions for single-phase motors, including centrifugal switch failure

diagnostic techniques including the use of specialised test equipment, including growlers

electrical tests for continuity and insulation resistance tests; between windings and to earth of single and three-phase motors

testing, including the following:

DC test – to determine the stator resistance

no-load test – to determine the rotational losses and magnetisation current

locked rotor test – to determine the rotor and stator impedances

thermography and condition monitoring

dismantling three-phase motors, including application of ‘witness marks’

operation of a ’growler’ to perform voltage drop testing of armatures of the series or universal motor

electric motor control and protection, including:

reasons why motor protection is required

Australian/New Zealand Wiring Rules and local supply requirements for three-phase motor installations and starters, including:

isolation and switching

automatic starting

emergency stopping

starting methods for limitation of starting currents

three-phase motor starters and their operating principles and characteristics, including:

DOL

star-delta

autotransformer

primary resistance

secondary resistance

various types of motor overload protection, including high rupture capacity (HRC) fuses

operating principles of magnetically activated over-current relays, thermally activated over-current relays and combined thermal-magnetic over-current relays

temperature-dependent resistor protection

under-voltage and over-voltage protection

single-phasing and reverse-phase sequence protection and the protection methods

types of enclosures to give environmental protection, including:

open - ends of machine are open allowing free ventilation with fan attached to the motor shaft to draw air through the motor

protected - protection obtained by fastening steel wire mesh or perforated metal over enclosures with fan attached to the motor shaft to draw air through the motor

drip proof - an advance on the protected motors with openings further protected by a hood to prevent foreign materials or moisture from falling vertically into motor

duct ventilated - air is drawn from outside through a duct or air is forced via a blower through a duct to the motor

totally enclosed - no contact between the air outside and inside the machine can be classified as waterproof, weatherproof or submersible

flameproof - totally enclosed motor with additional precautions, including to seal bearings and used where there are flammable gases and risk of explosion if spark enters the atmosphere

AS 1359.106-1996 Rotating electrical machines – General requirements – Methods for cooling (IC Code)

three-phase motor braking and the principles of operation of the major types, including mechanical, eddy current, dynamic, regenerative and plug

altering the speed of AC induction motors by varying the number of poles or frequency

VSDs, including:

methods and operating principles

installation requirements

shielding and filtering

harmonics and power factor

performance characteristics

set up and commissioning

common faults – their symptoms and causes

three-phase synchronous machines – alternators:

construction and operating principles

excitation and generated voltage

effect of load on alternator voltage

effect of power factor on output voltage of an alternator

voltage regulation

alternator ratings expressed in kVA

parallel operation of alternators – synchronising and the methods used to achieve synchronisation, including the use of a synchroscope

effects of a change in excitation when connecting two alternators in parallel

three-phase synchronous machines – motors:

construction and operating principles

effect of a load on a synchronous motor

effect on varying the field (DC) excitation, including changes in power factor

hunting in three-phase synchronous machines and the methods used to reduce this effect, including the use of amortisseur windings in the pole faces of the rotor

starting methods and applications of three-phase synchronous motors

single-phase synchronous motors:

the primary purpose and the major types: reluctance and hysteresis motors

applications of single-phase synchronous motors

standby power supplies including uninterruptable power supplies (UPS) and the purpose they provide, i.e. mains power at a specified voltage and frequency

standby engine driven alternators starting methods and sequence of operation

non-rotating AC equipment and components including construction, operation and application of:

linear motors and actuators

solenoids, relays and contactors

welders and other non-rotating AC machines.