Certification Assistance for Marine Engineers
Canadian
First Class ME
ElectroTech
In Canada, Transport Canada administers the Marine
Engineering examination process; visit the
Training Page for details
on the process. The actual exam consist of nine (9) questions randomly drawn
from a question bank of the various subject. Six (only) must be answered in a
3.5hrs time frame. The exam questions are similar to these, presented below,
and are drawn heavily from similar question in the Reed's Marine Engineering
series of books.
Disclaimer
Transport Canada has ask us to advise users of this webpage
to keep in mind that these questions are not the exact questions found in
their exams. Martin's Marine Engineering Page - www.dieselduck.net
is not affiliated with Transport Canada and these questions have been gathered
from various sources.
1. To find the resistance of a coil,
an ammeter and a voltmeter are used. The ammeter which has a resistance of 0.005 ohm, is connected in
series with the coil, and the voltmeter, which has a resistance of 5000
ohms is connected across the ends of the coil. When the voltmeter registers 210 volts the ammeter registers 3
amperes. The resistance of
the coil was then calculated from the voltmeter reading divided by the
ammeter reading. Calculate
the % error in this value.
Ans: P47 V2
2. Given a meter movement that has
full scale deflection current of 0.015 A and 5 ohms resistance, calculate
the shunt resistor required to use this meter in a 20 ampere circuit
and also the multiplier resistor
that would be necessary to use it in a 50 volt circuit.
Ans: P8 V2
3. Two lamps with the following
characteristics are to be connected in series across a 230 volt supply. A
lamp is 110 volts and 40 watts whilst the other is 100 volts and 150
watts. Indicate by a sketch and calculation how they can be connected so
that they operate within their characteristics.
note: resistors may be used to
complete the circuit.
Ans: P70 V2
4. Calculate the current through the
2 ohm resistor.
insert diagram here
Ans: P69 V1
5. A battery of six cells in series,
each cell has an e.m.f. of 1.5 volts and internal resistance of 0.5 ohms,
is connected to resistances of 6 ohms, 12 ohms separately at first and
then with the two resistances in parallel across the battery terminals.
Calculate the current through each resistance in each of the cases.
Ans: P34 V1
6. Six electric cells are connected
together in series, the e.m.f. of each cell is 1.2 volts and it's internal
resistance is 0.4 ohms. Three
wires A, B, and C whose resistances are 5, 40 and 200 ohms respectively,
can be connected between the battery terminals.
a) Determine the current which flows
when each wire is inserted separately
b) determine the current which flows
when they are inserted together as a parallel group
Ans: P25 V1
7. A parallel circuit consists of a
branch "A" of resistance 10 ohms, inductance 38 mH and
copacitance 312.8 uF, and branch B has negligible resistance and inductive
reactance of 12 ohms. Derive
graphically the total current and its phase angle, if the system is
connected to a 440 V 50 Hz
supply.
8. A lead wire and a copper wire are
connected together in parallel. The
currents flowing in the wires are in the ratio of 38 : 40 respectively and
the lead wire is 60% longer than the copper wire. The ratio of the specific resistances of the wires are: lead to
copper 208 : 16. Find the
ratio of the cross sectional area of the lead wire to that of copper.
Ans: P51 V2
9. An iron conductor and an aluminum
conductor are connected in parallel to a supply. The iron conductor is 10% longer and half the diameter of the
aluminum conductor. Given
that the ratio of the resistivities of iron to aluminum is 40 : 13 find
the ratio of the currents in the two conductors.
10. A wire is 60 meters long and
weight of 200 grams. A second wire is 70 feet long and weighs 6 oz. The specific resistance of the second wire is 10% less than that of
the first, and the material of the first wire is 2% less in weight per cu.
inch than the material of the second wire. Find the ratio of resistance of
the second wire to that of the first.
***imperial units?????
Ans: P24 V1
11. An electric heater consists of 8
elements connected in parallel to a 220 volt supply and heats up 10 tonnes
of oil 35o C in a 24 hour period. If
the specific heat of the oil is 2.17 kJ/kg oC and the efficiency of the
heater is 70% find:
a) the current taken
b) the resistances of one of the
elements if they are all of the same value.
Ans: P35 V1
12. An electric heater in a 220 Volt
circuit raises the temperature of 3 tonnes of oil by 50 degrees C every 12
hours. The efficiency of the
heater is 80% and the specific heat of oil is 2 kJ/kg oC. Find:
a) the power consumption in kWhours
b) the current taken
c) the resistance of the heater
element
Ans: P86 V1
13. a) Show how the electric
potential difference (volt) is related to energy (or work) and quantity of
charge.
b) Three capacitors of 2 uF, 3 uF
and 5 uF are connected to a 12 volt source, calculate the total charge of
the combinations when they are arranged in :
i) parallel
ii) series
Ans: P18 V2
14. State the definition of the
ampere in terms of it's coherence as a basic or fundamental unit in the
International System of Units (SI). Using
a sketch indicate what is meant by "fringing" and by
"leakage" in a magnetic circuit. What is the magnetic flux density at a distance of 5 cm from a very
long straight wire carrying a current of 150 A. Include units in your numerical solution and show that your answer
has the correct units.
note: uo = 4 pi x 10-7
Ans: P34 V2
15. Explain the terms
"fringing" and "leaking" when related to a magnetic
circuit. A magnetic circuit
is built up of rectangular metal plates 60 mm wide, having a combined
depth of 80 mm and with the insulating material between the laminations
accounting for 10% of the depth. The
circuit has a mean length of 1.8 m with an air gap of length 3 mm and a
cross sectional area of 500 mm2. Assume
a leakage factor of 1.1, the relative permeability of iron as 2500 and the
permeability of space as 4 pi x
10-7. Calculate the
magnetomotive force required to produce a flux of 0.006 Wb across the air
gap.
Ans: P6 V1
16. A coil of 200 turns is rotated
at 1200 RPM between poles of an electromagnet. Flux density is 0.02
teslas. Axis
of rotation is at right angles to the field. Effective length of the coil is 0.3 meters, mean width is 0.2
meters. Assuming e.m.f. produced is sinuosoidal, find:
a) maximum value of e.m.f.
b) frequency
Ans: P51 V1
17. A moving coil permanent magnetic
instrument has a resistance of 10 ohms and the flux density in the gap is
0.1 teslas. The coil has 100
turns of wire and is of mean width 300 mm and axial length is 25 mm.
If a p.d. of 50 mV is required for full scale deflection, calculate
the controlling torque exerted by the spring.
Ans: P42 V2
18. The following results of
measurements were taken at intervals over a half cycle of A.C. voltage:
Time 0 0.45 0.95 1.5
2.1 2.5 3.1 3.9 4.5
5.0
(milliseconds)
Volts 0 20 36
40 37.5 33 32
31 20 0
Calculate:
a) the r.m.s. value of the voltage
b) the frequency of the waveform
Ans: P40 V2
19. A D.C. generator gave the
following O.C.C. when driven at 1000 R.P.M.
Field current (A) 0.2 0.4
0.6 0.8 1.0 1.2 1.4 1.6
Armature voltage (V) 32 58
78 93 104 113 120 125
If the machine is run as a shunt
generator at 1000 R.P.M. the shunt field resistance being 100 ohms. Find:
a) the O.C. voltage
b) the critical value of the shunt
field resistance
c) the O.C. voltage if the speed was
raised to 1100 R.P.M. the field resistance being kept constant at 100 ohms
20. Express each of the following
voltages in phasor notation and locate them on a phasor diagram:
V1 = 212.0 sin (wt + 45 deg)
V2 = 141.4 sin (wt - 90 deg)
V3 = 127.3 cos (wt + 30 deg)
V4 = 85.0 cos (wt -
45 deg)
V5 = 141.4 sin (wt + 180 deg)
Ans: P9 V1
21. Three currents of peak values 10
A, 17.32 A and 20 A respectively meet in a common conductor. The
17.32 current lags the 10 A current by 90 deg. electrical, and leads the 20 A current by 60 electrical degrees.
Find the value of the resultant current giving its phase relation
to the 10 A current.
Ans: P66 V1
22. Discuss the relationship between
r.m.s., average and Form factor. A
transformer has a primary voltage of 240 V and a secondary of 17200 V.
The primary resistance is 0.00033 oh m
and the secondary resistance is 13
ohms. The output is 10 kVA. Find the copper loss at:
a) full load
b) half load
c) 1 kVA
Ans P84 V1
23. A single phase power transformer
supplies a load of 20 kVA at a power factor of 0.81 lagging. The iron loss is 200 Watts and the copper loss is 180 Watts.
Find:
a) the efficiency
b) the load at which maximum
efficiency occurs
c) if the load is now changed to 30
kVA at a power factor 0.91 lagging find the new efficiency
24. The load taken from a single
phase supply consists of:
a) filament lamp load of 10 kW
b) motor load of 80 kVA at 0.8 power
factor lagging
c) motor load of 40 kVA at 0.7 power
factor leading
Calculate the total load taken from
the supply in:
a) kW
b) kVA
c) power factor
Find the mains current if the supply
voltage is 250 V. Repeat the problem with the loads using a three phase
supply and a voltage of 440 V.
25. More questions like these can be
found on Martin's Marine Engineering Page, click to www.dieselduck.net.
25. In the following circuit find:
a) impedance
b) Iline
c) power factor
insert diagram here
Ans: P89 V1
26. A circuit has a resistance of 3
ohms and an inductance of 0.01 henery. The voltage across this circuit is 60 V and the frequency is 50 Hz.
It is a series circuit. Calculate:
a) impedance
b) line current
c) power factor
d) power absorbed
Ans: P72 V1
27. Find the impedence and power
factor of an A.C. circuit consisting of two pieces of apparatus in series.
Piece "A" has a resistance of 2 ohms and inductive
reactance of 14 ohms and piece "B" has a resistance of 10 ohms
and a capacitive reactance of 6 ohms.
28. An inductive load takes a
current of 15A from a 240 V 50 Hz supply and the power absorbed is 2.5 kW.
Calculate:
a) the power factor of the load
b) the resistance of the load
c) the reactance of the load
d) the impedence of the load
Draw a phasor diagram showing
voltage drops and current components.
29. A 100 W lamp for a 100 V supply
is placed across a 200 V supply. What
values of resistance must be placed in series with it so that it will work
under its proper conditions. If
a coil is used instead of the resistor and if the resistance of the coil
is small compared to the reactance what is the inductance of the coil.
The frequency is 50 Hz. What
is the total power absorbed in each case?
Ans: P19 V2
30. A coil has a resistance of 15
ohms and an inductance of 0.05 H. Calculate
the impedance and power absorbed by the coil in watt when it is connected
to a 100 V 50 Hz A.C. supply.
Ans: P29 V2
31. A coil in an A.C. circuit has a
resistance of 15 ohms and an inductance of 0.02 heneries. If it is connected across a 250 V 50 Hz supply find the power
absorbed.
32. An inductive circuit of 50 ohms
resistance and 0.02 H inductance is connected in parallel with a capacitor
of 25 uF across a 200 V 50 Hz
supply. Find the current
taken from the supply and its phase angle 33. Given a 100 V supply with a
70 A current at 60 degrees lagging. Calculate:
a) the resistance
b) the impedance
c) XL inductive reactance
Ans: P41 V2
34. Given 220 volts, 60 Hz and a
series circuit with 50 ohms resistance, 0.01 Henery inductance and 8 uF
capacitance, find the line current and power absorbed.
Ans: P85 V1
35. Two coils are connected in
series, when 2 amperes D.C. are passed through, the voltage drops are 20
and 30 V respectively. When 2
amperes A.C. at 40 Hz is passed through, the voltage drops are 140 and 100
volts respectively. Find the
current when the circuit is connected to 230 V 60 Hz.
Ans: P47 V1
36. A coil when connected with a 120
V D.C. supply consumes 600 watts. When
the same coil is connected with a 260 V A.C. supply the consumption is
2400 watts. Find the
inductive reactance of the coil.
Ans: P26 V1
37. A coil has a resistance of 400
ohms and an impedance of 498 ohms connected to a supply of 200 V at 60 Hz.
The coil is then connected in series with a capacitor of 40 uF and
across a supply of 240 V at 50 Hz. Find:
a) the current that flows
b) the voltage drop across the coil
and capacitor
Ans: P24 V2
38. Given the following circuit
find:
a) IA
b) IB
c) ILINE
insert diagram here
Ans: P8 V2
39. For the parallel circuit
illustrated calculate:
a) equivalent impedance
b) line current
c) power factor
d) power supplied to the circuit.
insert diagram here
Ans: P12 V1
40. Two inductive coils of
resistance values 5 ohms and 8 ohms and inductance values 0.02 H and 0.01
H respecitvely are connected in parallel across a 240 V 50 Hz supply.
Find:
a) coil currents
b) the circuit current
c) the circuit power factor
41. How can the power factor be
improved in an A.C. system? How would methods to improve the power factor
effect the power consumed?
Ans: P78 V1
42. A 50 kW A.C. generator has a
power factor of 0.7. The
power factor is raised to 0.8 with the same kVA, find the % increase in kW
output.
Ans: P89 V1
43. For what purpose are
transformers fitted in the electrical system of a ship? The windings of a 10 kVA 2400 240 V 60 Hz transformer has
resistances of 6 ohms and 0.06 ohms. If the total loss at full load is 268
watts, find the copper loss and the core loss at the condition stated.
Ans: P60 V1
44. Sketch the open circuit test on
a transformer clearly showing all the instruments. The following readings were taken on a 400 to 220 V
transformer on the open circuit test.
Ammeter reading 0.18 Amps
Wattmeter reading 12 Watts
Find:
a) the magnetising component of the
no load current
b) iron loss component
c) the transformation ratio
45. Sketch and describe the
construction of a current transformer. What other salient features are incorporated to make the machine
efficient? Why must the
secondary circuit of a current transformer never be opened when the
primary is energized?
Ans: P64 V1
46. Sketch and describe a linear voltage differential transformer. Give some applications
of the L.V.D.T. slug.
47. Given the following data on a
transformer, calculate the primary voltage and turns ratio. Also calculate the primary and secondary current.
Data: secondary voltage 13200 V
primary turns 900
primary flux 1 x 10-3
output 440 kVA 60 Hz
Derive the formula used in this
problem
Ans: P76 V1
48. Describe the construction of a
transformer and what are it's functions? A transformer has a primary winding of 800 turns and a secondary of
160 turns. It is rated at 10
kVA at 480 V. Find:
a) ratio of transformation
b) approximate primary voltage
c) rated full load secondary current
d) rated full load primary current
neglecting " no load" current
Ans: P46 V1
49. There is a method of connecting
a transformer to obtain a two phase three wire secondary output from a
three wire three phase input. Sketch
a diagram to show how this would be accomplished using the SCOTT TAP
method. Show the
position of the tap in the sketch.
Ans: P38 V2
50. Three phase transformers may be
connected in banks in the following manner:
a) delta delta
b) delta wye
c) wye wye
d) wye delta
Discuss the particular application
each would be used for and state the advantages or disadvantages ensuing
from such application.
Ans: P49 V1
51. Give the advantages of using
ultra high voltages in the transmission of electric power between the
source of generation and the load point. A transformer with a rating of 2400 - 240 V has 2000 turns on the
primary winding. Assuming a 3% voltage drop in the transformer when fully
loaded, how many turns should be placed on the secondary to maintain its
rated voltage at full load. With
this number of turns on the secondary and the primary voltage held
constant, what is the secondary no-load voltage?
Ans: P51 V2
52. For the " no load "
test on a transformer, the ammeter was found to read 0.18 A and the
wattmeter 12 W. The reading
on the voltmeter was 400 V. Calculate:
a) the magnetizing component of the
" no load " current
b) the iron loss component
c) the transformation ratio
Ans: P51 V2
53. A three phase, marine dry type
transformer is used to step down the voltage of a three phase, star
connected alternator to provide the supply for 120 V lighting. The transformer has a 4 : 1 phase turns ratio and is delta
connected on the primary side and star connected on the
secondary side. If the lighting is supplied at the line voltage of the transformer,
what must be the phase voltage of the alternator.
54. Illustrate a 3 phase power
supply utilizing 220 V for power purposes and 110 V for lighting. If the loads are unbalanced sketch a system that will accommodate
the unbalance.
Ans: P7 V2
55. A delta primary and star
secondary transformer of 200 kVA capacity has a primary voltage of 6600 V
and secondary voltage of 440 V 3 phase. If this transformer is loaded with a 110 kW motor that takes 440 V
60 Hz with a p.f. of 0.8 and an efficiency of 83%, find the phase current
in the primary.
Ans: P88 V1
56. A 6 pole three phase 550 V 60 Hz
induction motor has a 5% slip and draws a current of 30 A when delivering
a shaft torque of 150 Nm. Assume
windage and friction losses amount to a torque of 10 Nm and the iron and
copper loss at 900 W. Calculate:
a) motor speed
b) brake power
c) input power
d) power factor
e) efficiency
Ans: P10 V1
57. A 500 V three phase alternator
supplies a balanced delta connected load in parallel with a balanced star
connected load. The delta
load is 30 kW at a power factor of 0.92 (leading) The star load is 40 kW
at a power factor of 0.85 (lagging). Calculate the line current and the power factor of the supply.
Ans: P85 V1
58. A 3 phase 440 V 60 Hz six pole
induction motor develops 18 kW on full load with a speed of 1164 R.P.M.
and operating power factor of 0.88 (lagging). Calculate the full load:
a) slip
b) input in kW
c) line current
note: the stator loss is 1.7 kW and
mech losses total 1.5 kW
Ans: P29 V2
59. A 3 phase 6.6 kV 60 Hz
alternator has an equivalent armature reactance of 5 ohms per phase and
negligible resistance. It is
connected to bus bars which are energized by a second identical
alternator. The breaker is
closed when both armatures are rotating at 1800 R.P.M. but 2 electrical
degrees out of phase.
Calculate:
a) synchronizing current
b) synchronizing torque
Ans: P44 V1
60. An electrical system load
consists of a 300 kW induction motor power factor 85% and 100 kW lighting
load with power factor 100%. It
is proposed to increase the system power factor to 95% by employing a 100
kW synchronous motor. Find:
a) the kVA of the synchronous motor
b) the power factor of the
synchronous motor
Ans: P58 V1
61. A 440 V single phase motor is
rated at 7.5 kW and operates at a power factor of 0.8 with an efficiency
of 88%. Find the current taken from the supply.
62. A shunt generator delivers 50 kW
at 250 V at 400 R.P.M. The armature and field resistances are 0.02 ohm and
50 ohms respectively. Calculate
the speed of the machine when running as a shunt motor taking 50 kW input
at 250 V. Allow 2 volts for
brush contact drop. Assume
flux to be proportional to field current.
Ans: P63 V1
63. A fresh water pump is found to
take an armature current of 25 A at 220 V when running on full load.
The speed is measured to be 725 R.P.M. and the armature resistance
is 0.2 ohm. If the field
strength is reduced by 10% by means of the speed regulator and the torque
remains unchanged, determine the steady speed ultimately attained and the
armature current.
Ans: P77 V1
64. Find the generated e.m.f. per
conductor of a 6 pole D.C. generator having a magnetic flux per pole of 64
mWb and a speed of 1000 R.P.M.. If
there are 468 conductors, connected in six parallel circuits, calculate
the total generated e.m.f. of the machine. Find also the total power developed by the armature when the
current in each conductor is 50 A.
Ans: P88 V1
65. A six pole three phase generator
generates 200 V 60 Hz with a field current of 4 Amps. If the speed is changed to 1400 R.P.M. and the field current to 3
A, determine the generated voltage.
66. A D.C. shunt motor is wave wound
and has four poles. The flux
per pole is 2.5 x 10-2 weber. Armature
current is 200 A the supply voltage is 230 V. Conductors = 294. Armature resistance = 0.35 ohm.
Calculate the R.P.M. and torque.
Ans: P9 V2
67. The curve of induced e.m.f.
against excitation current for a separately excited generator when run on
no load at 1200 R.P.M. is given by:
e.m.f. 15
88 146 196 226 244
254
Excitation 0 0.4
0.8 1.2 1.6 2.0 2.4
current
Deduce the voltage to which the
machine would self-excite if the shunt field resistance was set at 90 ohms
and the machine was run at 900 R.P.M.
Ans: P41 V2
68. A pump delivers 12700 liters per
hour of water into a boiler working at 15 bars. The pump is 82% efficient and is driven by a 220 V motor,
having an efficiency of 89%. Calculate the current taken by motor.
note: 1 liter of water = 1 kg
note: 1 bar = 105 N/m2
Ans: P22 V2
69. A shunt motor operates at 1200
R.P.M. and the supply voltage is 220 V. The current is 60 A and the shunt field resistance is 110 ohms.
The armature resistance is 0.15 ohms. What percent variation in speed will there be if the torque is
reduced to 50%.
Ans P27 V1
70. A compound wound long shunt D.C.
motor has an output of 150 A at 220 V. The equivalent resistances of the armature, series and shunt fields
are 0.025, 0.015 and 176 ohms respectively. There is a 2 volt drop across the brushes. Find the induced
voltage.
Ans: P45 V1
71. A 460 V D.C. motor takes an
armature current of 10 A at no load. At full load the Ia is 300 A.
If the resistance of the armature (Ra) is 0.025 ohm, what is the
value of the back e.m.f. at "no load" and "full load".
Ans: P65 V2
72. Determine the resistance of each
step of a starter for the following motors:
10 h.p. 240 V armature resistance
0.5 ohm and full load current limited to 45 amps.
note: the starting current to be
150% of full load current
Ans: P66 V2
73. Illustrate the construction of
an induction motor. Describe how it operates and explain the difference
between it and a synchronous motor.
Ans: P90 V1
74. Discuss the difference between
synchronous motor and induction motor. How is a synchronous motor started?
Ans: P82 V1
75. What is the theory of operation
of an A.C. synchronous motor? Why
is there no starting torque? In
an 8 pole synchronous motor what would the speed of rotation be at:
a) 60 Hz
b) 50 Hz
76. Discuss the functions of the
following elements of an automatic voltage regulator for an alternator:
a) error detecting element
b) correcting element
c) stabilizing element
Ans: P19 V1
77. Discuss a synchronous motor. State two main functions of the damper winding.
Ans: P82 V1
78. Sketch and describe a motor
controll starter for a synchronous motor. How are: overload, winding damper, breaker incorporated into the
circuit.
79. Explain what a damper winding
is. Sketch it and where would
you find them. A three phase
3.3 kV 50 Hz alternator
having an equivalent armature reactance of 5 ohm per phase and negligible
resistance is connected to bussbars to which an identical alternator is
already connected. The
circuit breaker was closed at an instant when the rotors of the two
machines were running at 1500 R.P.M. but out of phase by 1 mechanical
degree. Calculate:
a) the synchronizing current
b) the synchronising torque at this
instant
80. Describe frequency as pertinent
to A.C.. A four pole A.C. generator runs at 1500 R.P.M., what is it's frequency?
If this generator supplies current to a 40 pole motor, find the
speed of the motor:
a) if it is synchronous
b) if it is induction with slip of
2%
Ans: P52 V2
81. A six pole three phase 50 Hz
induction motor is running at full load with a slip of 4%. The rotor is star connected and it's resistance and standstill
reactance are 0.25 ohm and 1.5 ohm respectively. The e.m.f. between the slip rings at standstill is 100 V.
Find the full load conditions:
a) the e.m.f. induced in each rotor
phase
b) the rotor impedance per phase
c) the rotor current and p.f.
assuming the slip rings are short circuited
Ans: P65 V2
82. A six pole three phase 60 Hz
induction motor running at full load has a 4% slip. The rotor is star connected.
Rotor resistance is 0.25 ohms per phase. Standstill rotor reactance
is 1.5 ohms per phase. Standstill e.m.f. on the slip rings is 100 V. Calculate:
a) the e.m.f. induced in each rotor
phase
b) rotor impedance per phase
c) rotor current and power factor
with shorted slip rings
83. Find the line current for a 440
V 3 phase motor which is 88% efficient and is rated at 110 kW. The current lags the voltage by 30 degrees.
Ans: P19.2 V2
84. A four pole alternator on open
circuit generates 200 V at 50 Hz when it's field current is 4 A. Determine the generated e.m.f. at a speed of 1200 R.P.M. and a
field current of 3 A neglecting saturation of the iron parts.
Ans: P25 V2
85. The terminal voltage of a shunt
wound generator is 150 volts and the current output is 70 amperes. If the resistance of the field windings is 30 ohms and that of the
armature conductors is 0.06 ohm, calculate the electrical efficiency of
the generator.
Ans: P26 V1
86. Sketch and describe a three
phase alternator. Explain how
to connect up two alternators in parallel, in particular state the
procedure for synchronizing.
Ans: P31 V1
87. Sketch and describe an A.C.
alternator. How is the
alternator excited?
88. An 8 pole alternator running at
720 R.P.M. supplies current to a synchronous motor with 48 poles. Calculate the frequency and speed of rotation of the motor.
Ans: P35 V1
89. A three phase 100 R.P.M. A.C.
generator supplies a 50 Hz current to a three-phase, 120 R.P.M.
synchronous motor. Calculate the number of poles on both the alternator
and motor.
90. A 440 V three phase eight pole
marine alternator generates a 50 Hz supply when dirven at normal speed.
If the system is to be converted to 60 Hz working, find the speed
at which the prime-mover is to run. Assuming
the same excitation value find the new system voltage
91. What causes overheating in a
squirrel cage motor? Discuss the preventive maintenance required on this
type of motor.
Ans: P91 V1
92. Discuss the reasons for an
induction motor overheating. Discuss preventive maintenance which whould
be carried out on induction motors. How
would you reverse the direction of an induction motor?
93. Define: (as applied to D.C.
starters)
a) current limit
b) time limit acceleration Sketch
the diagram for one of the above types for a 1.5 kW wound motor.
Ans: P91 V1
94. Describe a magnetic motor
starter for an A.C. three phase, two speed motor (full voltage). Illustrate the answer with a simple circuit diagram.
Show the protection devices, control station, contactors and coils.
Ans: P19.1 V2
95. A D.C. starter is used for a
shunt wound motor utilizing 230 V. If
the armature resistance is 0.6 ohm and the maximum permissible is 50
amperes and minimum at 40 amperes. Find
the first resistance.
Ans: P89 V1
96. a) Describe an "air circuit breaker" .
b) Sketch and describe an "arc
chute".
c) Define "reverse power
relay"
Ans: P19.2 V2
97. Define each of the following
terms as related to an A.C . motor starter enclosure. Define:
a) "disconnect"
b) "Short circuit
protection"
c) "Overload protection"
d) "Start / Stop control"
Draw a simple diagram of a 3 phase
A.C. motor starting circuit which embodies these features
Ans: P42&43 V2
98. Sketch a D.C. shunt motor
Automatic Starter showing all protection devices, etc. It should
incorporate a time limit acceleration application. Explain it's operation.
Ans: P19.1 V2
99. Describe the functions of a D.C.
motor manual drum controller,illustrate your answer with a simple circuit
diagram.
Ans: P54&55 V1
100. Describe a circuit breaker as
fitted on the electrical switchboard in the engine room of a ship, and
explain how it functions. Illustrate your answer with a sketch.
Ans: P16 V2
101. Draw a simple circuit diagram
for a 3 phase A.C. motor incorporating the following
a) "motor delta wound"
b) "overload protection"
c) " short circuit
protection"
d) "disconnect"
e) "reversing"
f) "magnetic contactors"
g) "push button stn."
h) "Indicator lamps"
State the frequency of operation
when Fwd. and Rev. buttons are pushed. What protection is provided against
the possibility of pushing the Fwd. and Rev. buttons at the same time?
Ans: P77a V1
102. Describe an "air circuit
breaker" suitable for 600 V A.C. installation. Sketch some type of "arc chute" with the
above breaker and explain how it functions to dissipate the arc.
Ans: P42 V1
103. Describe the functions of a
D.C. motor manual drum controller: Illustrate your answer with a simple
circuit diagram. A 25000 ohms voltmeter and a 35000 omhs voltmeter are
connected in series across a 500 volt line. What will each meter indicate?
Ans: P54 V1
104. Describe a motor controller
suitable for a synchronous system. Illustrate your answer with a simple
circuit diagram and include an explanation of the starting sequence. Why
are overload and damper winding protection fitted in the circuit.
Ans: P62 V1
105. Sketch and describe a 3
terminal rheostat type starter for a D.C. motor.
Ans: P84 V1
106. Describe a starter that could be used for an A.C. motor application of full
voltage, single speed, suitable for 750 W at 115 volt. Show in your sketch
the protection devices, control station, contacts and hold in coil.
Ans.: P38 V2
107. Sketch and describe the
operation of a two speed A.C. induction motor starter. Your sketch is to include all safety and protective devices.
The line voltage is 440 V.
108. Describe and sketch a simple
manual starter for a D.C. shunt motor and indicate why it is necessary to
use this device to start the motor.
Ans: P22 V2
109. In the sketch shown, determine
the resistance of each step of the starter for the following motor.
10 hp. at 240 volt with an armature
resistance of .5 omh and full load current of 45 amps. Starter current to
be 150% of the full load current.
insert diagram here
Ans: P66 V2
110. Describe and diagrammatically
sketch a main switchboard for a vessel having three D.C. current
generators. Indicate on your sketch all the necessary fittings, meters
etc. and explain the purpose of each.
111. Assuming one generator is on
load, describe the procedure necessary to bring the two machines on to the
bussbar so that the three generators may run in parallel.
Ans: P37 V2
112. Sketch a D.C. switchboard
suitable for paralleling two D.C. generators, show all instruments,
switches and controls.
Ans: P37 V2
113. Sketch an A.C. switchboard
suitable for paralleling two synchronous generators. Your sketch is to show all protective devices and circuit
breakers. Find the line
current supplied to a 12 kW motor which is 84% efficient at a power factor
of 0.8 and 44 V.
114. Sketch and describe a main
breaker.
115. Enumerate the advantage and
disadvantages of a D.C. electrical installation (for lighting and
auxiliary purposes) as compared with a similar A.C. system. What instruments are required on the switchboard for each of
these systems? State the
functions of the instruments named.
Ans: P28 V1
116. Discuss the starting sequence
of an emergency generator which starts, automatically, in the event of a
main power failure.
Ans: P81 V1
P17 V2
117. Make a sketch of a ships
switchboard suitable for paralleling two or more D.C. generators. What is
the reverse current relay and the overload relay and why are they
necessary? State the procedure for paralleling a D.C. generator.
Ans: P37 V1
118. Describe with sketch a
balancing arrangement for a 3 wire Edison system to provide 110 lighting
and 220 volt power.
Ans: P70 V1
119. Detail a method of converting
the measurement of the level of a liquid in a tank and the RPM. of a shaft
into an electrical signal for input into a data logger.
Ans P16 & 17 V1
120. Using a sketch to illustrate
and amplify your answer describe any one of the types of frequency meters
listed below:
1) vibrating reed type
2) moving disk type of frequency
meter
3) electrodynamic type
Ans: P31 V2
121 Describe the "megger".
How is it used in testing circuits and equipment.
Ans: P38 V1
122. Describe an electric propulsion
system employing a turbine driven alternator and D.C. propulsion motor.
Use a sketch to help illustrate your answer. Why is the propulsion system
made more complicated by employing A.C. and D.C. rather than the use of
only one or other of these power modes. What type of rectification
arrangements would likely be used in such a system.
There is a physical limit to the
max. power available as output for which a direct current motor can be
built. How does the designer overcome this restriction if much greater
power per shaft is desired.
Ans: P30 & 31 V2
123. A boiler turbine generates
electrical power in an industrial situation. It operates at 15000 kPa and 520oC. Make a block diagram showing a
closed loop for control of the system showing any safety devices. Give a general description of any electronic or other devices used
in this control system.
124. A steam turbine is used to
generate power on a vessel. Sketch a block diagram of the control circuit
showing the alarms, shutdowns and other safety devices.
125. More questions like these can
be found on Martin's Marine Engineering Page, click to www.dieselduck.net.
125. Describe a typical impressed
cathodic protection system used in a ship. What are the values of current
and voltage used? What problem may be encountered if a current appreciably
higher than recommended by the equipment supplier is applied.
Ans: P73,74,75 V1
126. Describe the construction of a
semi-conductor rectifier indicating the materials used. Sketch the output
wave of the bridge rectifier illustrated If a capacitor was connected
across the output terminals, what effect will it have on the waveform?
insert diagram here
Ans: P15 V1
128. Describe the following:
a) semi-conductor
b) valence
c) hole
d) ion
e) forward bias
f) reverse bias
g) "p" type material
h) "n" type material
i) majority carriers
129. Discuss the precautions
required when electrical equipment is to be used in flammable atmospheres.
What is meant by the terms:
1) intrinsically safe circuits
2) flame proof apparatus
Ans: P21 V1
130. Describe an emergency lighting
system which uses batteries. What care and maintenance does this system
require? How are the batteries charged when the available power is A.C.
Make a line diagram of such a circuit.
Ans: P61 V1
131. The circuit illustrated is that
of a typical common-emitter amplifier. If the current through the emitter
resistor is .5 mA, determine the battery voltage. Assume a base emitter
voltage drop of .1 volt.
insert diagram here
Ans: P14 V1
132. Describe any emergency power
installation fitted aboard ship. State the circuits this generator feeds
and list the various connections on the switchboard of this installation.
Ans: P28 & 81 V1
133. Sketch and describe an
emergency switch board for a large passenger vessel.
134. Sketch and describe a photo
electric cell or ? tube. Give
two uses on a boiler
135. Sketch a fluorescent tube. Describe how it produces visible light.
What is a ballast?
136. Given the following equation:
[ Eo =
1 C2
] [ uo = 4 pi x
10-7 Wb]
4 pi x 8.98776 x 109
Nm2
Am
a) Show that the correlation between
both of these quantities is numerically equivalent to the velocity of
light.
b) Using dimensional analysis show
that the units required for "C" are consistant with the formulae
in part "a".
137. What are damping bars and why
are they fitted to A.C. generators and synchronous motors.
Disclaimer
Transport Canada has ask us to advise users of this webpage
to keep in mind that these questions are not the exact questions found in their
exams. Martin's Marine Engineering Page - www.dieselduck.net
is not affiliated with Transport Canada and these questions have been gathered
from various sources.