UEEEL0077 — Evaluate and report on the performance of LV machines

Elements & performance criteria

Performance evidence

• evaluating the operating parameters of existing machines
• recommending alterations to an existing machine for compliance with specified operating parameters
• justifying selection of machines/circuits to comply with a specified function and operating parameters
• determining the cause of problems in an existing machine
• determining solutions for problems in an existing machine
• determining conditions causing an existing machine to be unsafe
• recommending solutions for identified machine problems
• determining correct machine for a specified range of applications
• determining parameters for the equivalent circuit using data from short circuit and open circuit tests
• determining percentage resistance, reactance and impedance of a transformer
• determining voltage regulation using percentage resistance, percentage reactance and load power factor
• determining parameters for maximum regulation and zero regulation

Knowledge evidence

• single and three phase transformers including:
• transformer construction including:
• types of lamination style and core construction used in single-phase, three phase, double wound, auto transformers and instrument transformers
• identification of different winding styles/types used in transformers
• methods used to insulate low and high voltage transformers
• construction of transformer tanks for distribution transformers
• transformer auxiliary equipment
• function of transformer auxiliary equipment
• types of information stated on transformer nameplates
• application of transformers
• performing basic insulation resistance, continuity and winding identification tests
• transformer operation including:
• principles of mutual induction of a transformer
• factors that determine the induced voltage in a transformer winding
• determining the value of a transformer’s secondary voltage and current given one winding’s electrical details and the turns ratio
• identification of voltage and current components of a phasor diagram for a transformer no-load and load
• principles of power transferred from the primary to the secondary when a load is connected using a phasor diagram neglecting impedance drops
• selecting transformers for specific application/s
• security features specified in AS/NZS3000 with respect to transformers and isolating transformers
• transformer resistance, reactance and impedance, including total equivalent values, referred to the primary and the secondary
• equivalent circuit of a transformer
• harmonics in transformers, including their generation, measurement, problems they cause and overcoming their impact
• the purpose of tertiary windings
• transformer losses, efficiency and cooling including:
• power losses which occur in a transformer
• tests which allow the power losses of a transformer to be determined
• determination of transformer losses and efficiency using test results
• efficiency for loads other than full load
• relationship between transformer cooling and rating
• methods used for natural and forced cooling of transformers
• properties of transformer oil
• tests conducted on transformer oil
• transformer voltage regulation and percent impedance including:
• voltage regulation as applicable to a transformer
• reasons for voltage variation in the output of a transformer
• determine the voltage regulation of a transformer from voltage and percentage impedance values
• percentage impedance as applied to transformers
• determine the percent impedance by using test results
• determine percent impedance of a transformer by calculation
• approximate voltage drop and exact voltage drop equations
• parallel operation of transformers and transformer auxiliary equipment including:
• determine polarity markings for an unidentified single phase double wound transformer
• need for parallel operation of transformers
• conditions/restrictions required before two transformers can be connected in parallel
• vector grouping
• connecting transformers in parallel to supply a single load
• loading on transformers operating in parallel
• the consequences/effect of an incorrect connection
• auto-transformers and instrument transformers including:
• identification of auto-transformers, voltage transformers and current transformers from their winding diagrams
• determining voltage and current in the windings of an auto-transformer by calculation
• advantages and disadvantages of an auto-transformer
• AS/NZS3000 requirements with respect to transformers
• construction and ratings of voltage transformers
• construction and ratings of current transformers
• precautionary measures taken to connect and disconnect instrument transformers
• connection diagrams for instrument transformers
• applications for auto-transformers and instrument transformers
• alternating current rotating machines including:
• operating principles of three phase induction motors including:
• characteristics of the magnetic field produced by a single-phase, two-phase and three-phase windings
• speed of rotation of a rotating magnetic field
• relationship between the rotor speed, slip and rotor frequency
• basic principle of operation of an induction motor
• reversing the direction of rotation of a three-phase induction motor
• three phase induction motor construction including:
• basic component parts of a three-phase induction motor
• types of rotors used in three-phase induction motors
• connecting a three-phase induction motor in both star and delta
• testing insulation resistance of a three-phase induction motor prior to connection to the supply
• testing winding resistance (ohmic value and continuity) of a three-phase induction motor prior to connection to the supply
• three phase induction motor characteristics including:
• relationship between torque, speed, and power and interpretation of speed/torque curves of induction motors
• squirrel cage motors operating characteristics conditions necessary for an induction motor to produce maximum torque
• operating characteristics of an induction motor from name plate information and by measurement
• induction motor efficiency and minimum energy performance standards (MEPS)
• full load efficiency and power factor of induction motors
• comparison of the advantages of squirrel cage and wound rotor induction motors
• single-phase motors – split phase including:
• common types of single-phase motors
• principles of operation of split phase induction motors
• construction and basic characteristics of split phase induction motors
• applications of split phase induction motors
• operation of split phase induction motors
• single phase motors – capacitor including:
• identification of single-phase induction motors including capacitor start, capacitor start/capacitor run and permanent split capacitor (PSC)
• principles of operation
• operating characteristics and typical applications
• connection and running
• reversing the direction of rotation
• single phase motors –shaded pole including:
• principles of operation
• operating characteristics and typical applications
• connection and running
• reversing the direction of rotation
• single phase motors – universal including:
• principles of operation
• identification and functions of each of the basic parts
• operating characteristics and typical uses
• connecting, running and reversing
• motor protection including:
• reasons why motor protection is required
• requirements of the AS/NZS3000 Wiring rules with regards to motor protection
• types of motor overload protection
• operating principles of microtherm devices, thermal and magnetic motor protection devices
• electrical features of motor protection HRC fuses
• effects of under voltage and over voltage on motors and motor circuits
• effects of repetitive starting and/or reversing on motors and motor circuits
• special requirements for motor protection, in high humidity or moist environments, high temperature areas and corrosive atmospheres
• operating principles of phase failure protection
• selecting suitable protection devices for a given motor and starter combination
• three phase synchronous machines- operation principles and construction including:
• power transfer diagram of an a.c. synchronous machine
• need for the generation of a sinusoidal waveform
• principles of operation of a synchronous alternator
• principles of operation of a synchronous motor
• principles of operation of an asynchronous generator (induction generator)
• identification of main parts of a synchronous alternator/motor
• methods used to provide the excitation of a synchronous alternator/motor
• block diagram of an alternator voltage regulator
• advantages gained by the parallel operation of alternators
• starting methods of synchronous motors
• vee curves
• the behaviour of synchronous motors at various excitation levels and their associated phasor diagrams
• limits of stability for synchronous motors
• alternators and generators including:
• effects on the generated voltage of variations in excitation
• effects on generated voltage of variations in load
• identification of characteristic curves of an alternator
• types of prime movers used with single and three phase portable/standby alternators
• manual operation of single and three phase portable/standby alternators
• ratings of single and three phase portable/standby alternators
• applications of single and three phase portable/standby alternators
• construction details of single and three phase portable/standby alternators
• common faults found in portable/standby alternators
• limits of stability for synchronous alternators.

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