Guidance

Marine Electro-Technology Written Examination Syllabus

Published 6 May 2014

The expected learning outcome is that the student:

1. Electric Circuit Principles

1.1 Solves direct current (dc) linear circuit problems under steady and transient conditions.

1. States Kirchhoff’s current and voltage laws.
2. Solves steady-state dc circuit problems involving not more than three unknowns using Kirchhoff’s laws.
3. Predicts graphically transient voltage and current relationships in simple resistance-inductance (R-L) and resistance-capacitance (R-C) circuits when switched on and off a steady dc supply.
4. States the time constants of simple R-L and R-C circuits as τ = L/R and τ = CR respectively.
5. States the form of exponential growth and decay formulae applied to R-L and R-C circuits.
6. Uses exponential growth and decay formulae to obtain particular values of current or voltage at a given time or vice-versa in simple R-L and R-C circuits.

1.2 Solves dc non-linear circuit problems under steady-state conditions.

1. States that a non-linear device is one that does not obey ohm’s law.
2. Shows that a non-linear element may be described by its V/1 characteristic in a graphical or mathematical form.
3. Lists typical examples of non-linear devices eg generators, rectifier elements, transistors, thermistors etc.
4. Estimates dc and ac resistances of a non-linear element under given operating conditions.
5. Derives graphically an overall (dynamic) V/1 characteristic for a simple dc series or parallel circuit including a non-linear element and a linear resistor.
6. Solves simple dc non-linear circuits mathematically given the V/1 law of the non-linear element.
7. Solves simple dc non~linear circuits graphically using load-line technique or dynamic characteristics.

1.3 Understands operation of single-phase and three-phase ac circuits.

1. Describes using phasor diagrams, voltage and current relationships obtained in pure resistance, pure inductance and pure capacitance circuits when energised from a single phase sinusoidal ac supply.
2. Calculates impedance M of simple R-L-C circuit combinations in series and in parallel.
3. Defines circuit power factor as ratio of active power to apparent power and as cosφ = R/Z.
4. Solves simple series and parallel ac circuit problems including pf correction.
5. Sketches voltage and current phasor diagrams representing simple R-L-C series and parallel circuits.
6. Recognises that voltage and current resonance occurs when series and parallel R-L-C circuits respectively operate at unity power factor.
7. Derives f = 1/2π√LC as the resonant frequency of a series R-L-C circuit.
8. Defines active power (P), apparent power (S) and reactive power (Q).
9. Sketches a power triangle (P Q and S) to represent operating conditions in a single-phase circuit.
10. Solves single-phase circuit problems using P Q and S quantities.
11. Sketches the interconnection of three separate single phases to form 3-phase star and delta connections.
12. Sketches 3-phase voltage and current phasor diagrams to represent balanced star or delta connection.
13. Derives relationships V_L = √3 Vph for star and I_L = √3 Iph for delta balanced connections using phasor diagrams.
14. Shows mathematically that total 3-phase power is given as P = √3V_LI_LCosΘ for both star and delta connections.
15. Solves 3-phase balanced circuit problems using voltage, current and power relationships.

2. Electronic Circuit Principles

2.1 Understands the operation of junction diodes in rectification circuits.

1. Recognises typical forward and reverse V/I characteristics for Si and Ge diodes.
2. Compares half-wave, bi-phase and bridge rectification circuits supplied from single and three phase power supplies.
3. Sketches typical dc output waveforms from rectifier circuits in 2.1.2.
4. Calculates mean dc voltage at output of half and full-wave single-phase circuits given the ac input supply and vice-versa.
5. Describes the action of a simple C-only smoothing circuit in conjunction with a rectifier.
6. Tests complete dc power supply circuits.

2.2 Understands the operation of the Thyristor as a controlled rectifier.

1. Describes the construction of a thyristor as a 4-layer p-n device with anode, cathode and gate terminals.
2. States bias voltage polarities necessary for “turn-on” of a thyristor.
3. States conditions necessary for thyristor turn-off.
4. Sketches simple circuit diagram of series connected thyristor controlling a dc load from an ac supply (no gate circuitry required).
5. Describes circuit action of 2.2.4 under variable phase shift gate pulse control and block firing control.
6. Sketches typical load current and voltage in a simple ac driven thyristor controller with variable phase shift gate control.
7. Tests a complete single-phase thyristor power controller.

2.3 Understands the function of a Zener Diode as a dc voltage stabilizer.

1. Defines voltage stabilisation as the ability of a power supply to maintain its output voltage against changes in loading and input voltage.
2. Describes the action of a p-n junction Zener diode with forward and reverse bias voltages applied.
3. Recognises that a Zener diode must be worked with reverse voltage bias to become a stabilising element.
4. States that a Zener diode is rated in terms of its Zener voltage (V Z ) and its power handling ability.
5. Describes the action of a simple voltage stabilising circuit of a Zener diode and current limiting resistor in series across an unregulated dc supply.
6. Calculates values of voltages, currents and powers in a given simple dc stabiliser circuit under changes in supply voltage and loading conditions.
7. Tests a complete dc voltage stabiliser circuit.

2.4 Understands the action of a transistor and its function as a switch and signal amplifier device.

1. Describes the basic construction of p n p and n p n bi-polar transistors.
2. Describes the current distribution in p n p and n p n transistors when the emitter-base junction is forward biased and the collector-base junction is reverse biased.
3. Defines dc current relationships as h_FB = I_c/I_e and h_FE = I_c/I_b.
4. Sketches the basic common-base, common-emitter and common-collector connections of a transistor.
5. Recognises static transistor characteristics in common-emitter and common-base mode.
6. Describes the “cut-off” condition of a transistor when the base-emitter junction is zero or reverse biased.
7. Describes the “fully-on” (saturated) condition of a transistor when the base-emitter junction is heavily forward biased.
8. Compares cut-off and saturation of a transistor with an ideal electric switch.
9. Describes the action of a simple transistor switching circuit used for alarm and/or control purposes.
10. Sketches a practical common-emitter circuit arrangement showing dc bias arrangements, temperature stabilisation resistor and input and output signal connections.
11. Describes the action of a common-emitter circuit as a small-signal amplifier.
12. Draws a load-line onto the static output characteristics of a transistor to predict current gain.

3. Generation

3.1 Understands the principles of operation of a dc generator.

1. Reviews basic operation of a dc generator.
2. Derive the emf equation E = (2pΦ)(Z/A).
3. Evaluates generated emf.
4. Describes self excitation and states factors which may prevent it.
5. Estimates generated emf from magnetisation curve and given shunt field resistance.
6. Estimates critical shunt field resistance from a given magnetisation curve.
7. Sketches field and armature circuits for shunt and compound wound machines (long shunt and short shunt).
8. Explain voltage control using shunt field regulator.
9. Describes armature reaction and its effects.
10. Describes commutation, its effect and method of improving commutation eg brush shifting and interpoles.
11. Solves problems involving E, V, Ia, Rf and Ra.
12. Sketches V/I load characteristics of shunt and compound generators (cumulative and differential connections).
13. Estimates voltage regulation from (E - V)/V.
14. Lists typical marine applications of generators in 3.1.7.
15. Calculates series turns required to produce given terminal voltage on load.
16. Describes the connection of a dc compound generator to live busbars and effects of varying excitation.
17. Explains the use of the equalising connection.
18. Describes method of disconnecting a generator from the busbars.
19. Solves load sharing problems graphically and mathematically for shunt and compound generators.
20. States the reasons for a dc generator failing to excite.
21. Describes the methods of exciting dc generators that have lost their residual magnetism.
22. Explains the need for preference trips.
23. Describes, with the aid of a schematic diagram, the operation of a preference trip.
24. Explains the need for a reverse current relay.
25. Describes the operation of a reverse current relay.

3.2 Understands the principles of operation of alternating current (ac) generators.

1. Describes the arrangement of an armature winding to produce a three phase emf.
2. Sketches wave form diagram of three phase voltages.
3. Derives relationship between frequency, poles and speed.
4. Derives emf equation E = 2⋅22.Φz.f.
5. Sketches equivalent circuit per phase including Eph, Xs assuming resistance to be negligible.
6. Explains the effect of load and power factor on terminal voltage.
7. Calculates emf given terminal voltage inductive load conditions and winding reactance.
8. Estimates voltage regulation from (E - V)/V.
9. Describes connection of a three phase generator to live busbars, disconnection and shut-down.
10. Explains the effects of operating:
    1. governor;
    2. field regulator.
11. Solves load sharing problems where information is limited to kW, kVA, kVAr.
12. Describes the construction of salient and cylindrical pole ac generators.
13. Appreciate the reason for the 2 types of rotor.
14. Explains why an AVR is required for ac generators.
15. Describes the methods of exciting ac generators.
16. Describes, with the aid of diagrams, how brushless ac generators are excited using:
    1. rectifiers;
    2. silicon controlled rectifiers (thyristors).
17. Describes, with the aid of a schematic diagram, the operation of a compounded ac generator.
18. States the advantages and disadvantages of:
    1. the insulated neutral system;
    2. the earthed neutral system for marine ac generators.
19. Explains the need for a reverse power relay.
20. Describes the operation of a reverse power relay.
21. Explains the need for preference trips.

4. Distribution

4.1 Understands typical arrangements of marine ac and dc distribution systems.

1. Calculates current distribution and load potentials in dc:
   1. radial feeders;
   2. ring mains;
   3. double fed systems using dissimilar voltages.
2. Describes three phase, three wire and four wire systems.
3. Calculates value of the neutral current in a three phase, four wire unbalanced system.
4. Describes the function of the transformer in an ac distribution system.

4.2 Understands the principles of operation of a transformer.

1. Relates induced emf to rate of change of flux linkages.
2. Derives voltages and currents from turns ratios of single phase transformer.
3. Derives emf equation E = 4⋅44.fΦz.
4. Sketches phasor diagrams on and off load lag pf only and solves related problems.
5. Sketches three phase connections e.g. star/delta, star/star etc. using correct terminal markings.
6. Solves problems involving three phase transformers using turns and voltage ratios.
7. Sketches circuit diagram of auto-transformer.
8. Explains principles of operation of auto-transformer.
9. Solves problems on auto-transformers involving voltages, turns and tapping point.
10. Lists losses which occur in transformers.
11. Calculates efficiency of a transformer given load conditions and losses.
12. Explains the need for instrument transformers.
13. Explains the reasons for earthing the secondary winding of instrument transformers.

5. Utilization

5.1 Understands the principles of operation of a dc motor. Reviews the basic operation of shunt, series and compound dc motors.

1. Derives speed equation n = (V - I_aR_a)/kΦ.
2. Explains speed control using shunt field regulator, diverter resistance, tapped field or armature voltage control methods.
3. Derives torque equation T = (pΦ)(Z/a), I_a/2π = kΦI_a.
4. Sketches torque/ armature current, speed/ armature current characteristics and derives from these torque/speed curves for shunt, series and compound motors (cumulative only).
5. Solves problems involving changing load, field and/or circuit conditions.
6. Lists the losses which occur in dc motors and generators.
7. Calculates constant losses from no-load input as a motor and hence estimates efficiency of motor or generator under load conditions.
8. Tests a dc motor using Swinburne test and assesses efficiency under stated load conditions.

5.2 Understands the principles and operation of the three-phase induction motor.

1. Explains the production of a magnetic field rotating at synchronous speed by a three phase stator winding.
2. Calculates slip given number of poles, frequency and motor speed.
3. Evaluates rotor frequency.
4. Shows that input to rotor equals motor input minus stator losses and that this input equals 2πTn_s watts.
5. Calculates rotor output = 2πTn_r watts.
6. Evaluates rotor resistive power loss from difference between 5.2.4 and 5.2.5.
7. Calculates motor output = 2πT₁n.
8. Calculates efficiency from 5.2.4 to 5.2.7.
9. Describes the construction of single, double-cage and slip ring motors.
10. Sketches typical torque/slip curves for single, double-cage and slip-ring motors.
11. Describes with the aid of sketches the following starters: D.0.L.: Star/Delta : slip-ring.
12. Explains the reasons why a motor may “single-phase”.
13. Describes the effect of a motor “single-phasing”
14. Describes the motor enclosures used in the marine environment.
15. Describes the methods of varying the speed of ac induction motors.

5.3 Understands principles of operation of 3-phase synchronous motor.

1. Relates synchronous motor to ac generator.
2. Describes pony motor and induction motor starting methods.
3. Describes effects of changing load and excitation.
4. Solves problems of pf improvement type.
5. States marine applications of the synchronous motor.
6. 1. Describes with the aid of a sketch, the operation of a fluorescent lighting circuit.
   2. Sketches a navigation lighting circuit.
   3. Describes, with the aid of sketches, how earth faults are detected for:
      1. 1-phase and
      2. 3-phase supplies.