THREE PHASE SUPPLY AND MOTORS

PU: Protection Units

Overview:

In this module you will be taught how to work and apply safe work practices and procedures in your day to day duties working as an electrical learner in the electrical environment

Key and critical concepts which you will learn:

  • Familiarise with the general safe work practices to be observed in the work place.
  • Recall the unsafe acts and unsafe conditions that can lead to accidents in the work place. Explain the role of good housekeeping and hygiene in the prevention of accidents and injury in the work place.
  • Explain the role of the correct care and use of tools and equipment in the prevention of accidents.
  • Name the different types of personal protective equipment that can be used to prevent accidents and state the instances where it must be worn. Recognise the different safety signs in general use in industry.
  • State the general safety precautions that electricians must take when working on electrical circuits and apparatus.
  • During this process you must adhere to certain specified requirements as listed in the Module.

Tools, consumables, machinery and equipment required:

  • Module book / learning material
  • Pen
  • Booklet to make notes

Application:

  • Any electrical work environment you will perform safe working procedure

Additional resources

  • Subject matter experts
  • In-company Standard Operating Procedures

CO-T: Identify Contractors, Overloads, Fuses and Circuit Breakers for Various Applications

Overview:

In this module you will be taught how to work and apply safe work practices and procedures in your day to day duties working as an electrical learner in the electrical environment

Key and critical concepts which you will learn:

  • Familiarise with the general safe work practices to be observed in the work place.
  • Recall the unsafe acts and unsafe conditions that can lead to accidents in the work place. Explain the role of good housekeeping and hygiene in the prevention of accidents and injury in the work place.
  • Explain the role of the correct care and use of tools and equipment in the prevention of accidents.
  • Name the different types of personal protective equipment that can be used to prevent accidents and state the instances where it must be worn. Recognise the different safety signs in general use in industry.
  • State the general safety precautions that electricians must take when working on electrical circuits and apparatus.
  • During this process you must adhere to certain specified requirements as listed in the Module.

Tools, consumables, machinery and equipment required:

  • Module book / learning material
  • Pen
  • Booklet to make notes

Application:

  • Any electrical work environment you will perform safe working procedure

Additional resources

  • Subject matter experts
  • In-company Standard Operating Procedures

MO-1-MW: Overhaul a Three Phase Motor

Overview:

You will be learning towards the outcome “overhaul of a three-phase motor

Key and critical concepts you will learn:

On completion of this module, you must be able to:

  • Completely disassemble a three-phase motor.
  • Do a complete mechanical and electrical inspection and test on all the relevant components and correct any faults that are detected.
  • Re-assemble the motor correctly, test it and put it back in service

During this process you must adhere to certain specified required as listed in the Module.
You will be assessed, when you are confident that you may achieve the outcomes as listed, to determine your competence as measured against the required criteria. This assessment will be in line with accepted best practices regarding assessment.
A practical and/or theoretical test will be set at the end of the module and must be completed without using references.

  • The correct procedures must be followed to clean, mark and disassemble the motor.
  • Bearings must be removed and refitted, using correct procedures learned in modules BIF, BRR -1, BRR- 2 and BRR- 3.
  • Cleaning, examining and testing of the components must be done correctly and in accordance with these notes.
  • The motor must be reassembled, using the correct procedures and without damage to components.
  • The reassembled motor must be tested and test-run and must be in good working order at the completion if the overhaul.

Tools, consumables, equipment and machinery required:

  • Three phase induction motor
  • Piece of wood or copper punch
  • Soft hammer
  • Set of spanners
  • Allen key set
  • Workbench

Prerequisite modules:

  • Safe use of hand skills

Additional resources:

  • In-company Standard Operating Procedures
  • Subject matter experts

MT-2: Test a Three Phase Induction Motor

Overview:

In this module you will be taught how to test a three phase squirrel cage induction before it put in use

Key and critical concepts which you will learn:

  • Correctly examine an electrical motor for mechanical soundness.
  • Correctly perform all the electrical tests required on a three phase induction motor.
  • Record all the test results on a standard check list and come to the correct conclusions about the condition of the motor

Tools, consumables, machinery and equipment required:

  • Work bench / table
  • Three phase squirrel cage motor
  • Insulation resistance test
  • Multimeter

Related modules:

  • CM-T

Application:

  • These motors can be used on any electrical environment as they are the driving workhorse in the electrical field. Typical examples will be pedestrial drill, compressors , pumps , conveyors ………

Additional resources:

  • Subject matter experts
  • In-company Standard Operating Procedures
  • SANS 10147

CM-T: Explain Induction Motors

Overview:

In this module you will be taught how the motor is constructed, what is a three phase motor, the principle of operation of the motor how it operates. You will also be learning the principles of operation of slip ring motors.

Key and critical concepts which you will learn:

  • Explain the basic construction of induction motors.
  • Explain the difference between the rotors of a squirrel cage induction motor and a wound-rotor (slip ring) induction motor.
  • Explain how a rotating magnetic field is produced in the stator of an induction motor.
  • Explain what is meant by the term “slip” of an induction motor, and calculate the synchronous speed and percentage slip of an induction motor if the number of stator poles and the motor shaft speed are given.
  • Explain how the starting current in a slip-ring induction motor is controlled.
  • Explain how the direction of rotation in an induction motor can be reversed.

Tools, consumables, machinery and equipment required:

  • Work bench / table
  • Three phase induction motor
  • Three phase slipring motor

Application:

  • The AC motors are the workhorse of the industry

Additional resources:

  • Subject matter experts
  • In-company Standard Operating Procedures
  • Electrical Trade Theory
  • Electrical Technology
  • Advanced information

TT-2: Explain Three Phase Transformers

Overview:

In this module you will be taught about the basic operation of the three phase transformer how it works, the construction of the three phase transformer, the loses and the cooling methods of the transformer

Key and critical concepts which you will learn:

  • Explain the difference between auto transformers and ordinary power transformers.
  • Briefly explain how transformers are cooled.
  • Explain the purpose of instrument transformers and how they are usually rated.
  • Explain the basic difference between a single phase and a three-phase transformer.
  • Explain, with the aid of simple diagrams, the two methods of connecting the windings of a transformer, and the relationship between the voltages and currents in the two methods.
  • Explain, with the aid of labelled diagrams, the four methods of connecting the primary and secondary windings of a three-phase transformer.
    • Draw the connection diagram of a three-phase auto-transformer

Tools, consumables, machinery and equipment required:

  • Module book / learning material
  • Pen
  • Booklet to make notes
  • Different types of transformers including autotransformer

Related modules:

  • TT-1

Application:

  • Any electrical work environment where you need to transmit power from one station to another, whenever you need to step up or down the voltage

Additional resources:

  • Subject matter experts
  • In-company Standard Operating Procedures

PS-T-2: Explain Three Phase Power Supplies

Overview:

In this module you will be taught how the three phase DC and AC is generated

Key and critical concepts which you will learn:

  • Explain the basic construction of a three-phase alternating current generator (alternator), using schematic diagrams.
  • Make a schematic drawing of the voltage graph of a three-phase AC supply, showing the correct phase displacement angle.
  • Briefly explain, with the aid of a schematic diagram, how power is transmitted from the power station to the end-user.
  • Explain why AC supplies are transmitted at a high voltage.
  • Explain, with the aid of simple diagrams, the different transformer connections used to obtain three-phase, three-wire balanced systems and three-phase, four-wire distribution systems.
  • Explain how a 220-volt AC supply for domestic use is obtained from a 380-volt AC supply.

Tools, consumables, machinery and equipment required:

  • Module book / learning material
  • Pen
  • Booklet to make notes

Related modules:

  • PST-1

Application:

  • Industries which generate electricity like but not limited Eskom, Roshcon, etc.

Additional resources

  • Subject matter experts
  • In-company Standard Operating Procedures