BVN TM ELEC3 ROTATING MACHINES AND TRANSFORMERS Head Office
Department Technology Equipment - V0 December 2009
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CONTENT 1 Objectives 2 Rotating machines and requirements 3
Transformers and requirements
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3 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Electrical equipment THIS MODULE IS MAINLY BASED ON
HO DTM/DT3 TRAINING REFERENCED SMS64
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1 Objectives
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5 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Electrical equipment Objectives To be familiar with
Classification Rules regarding rotating machines and transformers
Study of Classification Rules requirements for rotating machines
and transformers
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2 Rotating machines and requirements
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7 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Rotating machines TYPICAL PRODUCT DESCRIPTION AND
REFERENCE OF REQUIREMENTS FOR STUDY
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ASYNCHRONOUS MACHINE
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9 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Principle of an asynchronous machine Turning Magnetic
Field in the Stator Rotor carried by inducted currents/forces
Rotating machines Asynchronous machine
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December 2009 Asynchronous motor (induction motor) Most commonly
used type of motor (pumps, fans, thrusters). Simple and cheap
construction. High starting current (5 to 9 times the full load
current) necessity of starters to avoid damages on lines, and
voltage drops on the distribution circuits. Converter or special
arrangement are to be provided for speed variation or starting (ex:
star/delta starting, autotransformer, etc). Low power factor (0.8)
( = active power (kW) / apparent power (kVA) ) Low air gap : less
suitable to withstand harsh mechanical conditions Rotating machines
Asynchronous machine
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December 2009 Limitation of Foucault currents (heating phenomenon)
Rotating machines Asynchronous machine
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December 2009 T sensor Rotating machines Asynchronous machine
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December 2009 Rotating machines Asynchronous machine
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December 2009 Asynchronous motor : stator Rotating machines
Asynchronous machine
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December 2009 Asynchronous motor : rotor Rotating machines
Asynchronous machine
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December 2009 Asynchronous motor : rotor Rotating machines
Asynchronous machine
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December 2009 Rotating machines Asynchronous machine
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December 2009 Asynchronous motor : rotor Rotating machines
Asynchronous machine
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December 2009 Rotating machines Asynchronous machine
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December 2009 Rotating machines Asynchronous machine
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December 2009 Rotating machines Asynchronous machine
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December 2009 Rotating machines Asynchronous machine
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December 2009 Rotating machines Asynchronous machine
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December 2009 Wound rotor motor Rotating machines Asynchronous
machine
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December 2009 Nb: this curve is to be transmitted when the overload
test hasnt been done to check the capacity of withstanding a
momentary excess of torque Rotating machines Asynchronous
machine
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December 2009 N CeCe Alternator zone Motor zone NsNs g =1 g = 0 C
max Working in asynchronous motor mode Working in asynchronous
generator mode Rotating machines Asynchronous machine
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December 2009 Asynchronous motor : star / delta connections 380 V
220 V 380 V Star connectionDelta connection Rotating machines
Asynchronous machine
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December 2009 Insulation class When the motor is started, his
temperature starts to increase. Each insulating material has a
maximum allowable temperature, depending of his class (IEC 60085 ;
A : 105C, E : 120C, B : 130C, F : 155C, H : 180C). The sum of the
temperature rise and the ambient temperature is not to be above the
limit defined by the insulation class, minus a margin defined for
each electrical device. Operating a motor above the limit of its
insulation class reduces the motors life expectancy. Rotating
machines Asynchronous machine
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29 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Duty types S1 : Operation at a constant load
maintained for a sufficient time to allow the machine to reach
thermal equilibrium. S2 : Operation at a constant load maintained
for a given time, less than that required to reach thermal
equilibrium, followed by a time de-energized and at rest of
sufficient duration to re-establish machine temperatures within 2 K
of the coolant temperature. S3 : a sequence of identical duty
cycles, each including a time of operation at constant load and a
time de-energised and at rest. S4, S5, S6, S7, S9, S10 (less
important) Nb : the Duty type is an important parameter for the
choice of the motor Rotating machines Asynchronous machine
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December 2009 Starting of asynchronous machine Star delta starting
: windings of the stator are connected in star and afterwards in
delta Part winding starting : a part of the stator windings is used
to start the motor Transformer starting : the motor is connected to
a autotransformer Soft starting : the motor is connected to a
static converter Rotor resistors starting : several resistances are
connected to the rotor (wound rotor) Rotating machines Asynchronous
machine
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December 2009 Motor panel Efficiency = mechanical shaft power (W) /
electrical power (W) Motor speed Motor service: S1 permanent
service S2 temporary service S3 periodical service IEC Ambient
temperature (Nb: 45C for BV Rules) Isolation class Rotating
machines Asynchronous machine
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December 2009 Motor panel I starting Starting torque Rotating
machines Asynchronous machine
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December 2009 Wound Rotor Motor panel Rotor Voltage and Current
Used for sizing of variable resistances associated Rotating
machines Asynchronous machine
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SYNCHRONOUS MACHINE
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December 2009 Principle of an synchronous machine N S w S N w
Stator windings supplied by AC Voltage at certain frequency creates
a turning magnetic field (synchronism speed) Rotor windings
supplied by a continuous current that make the rotor acting like a
permanent magnet that try, at all time, to be in line with the
turning field of the stator (no slip) Rotating machines Synchronous
machine
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December 2009 Principles of synchronous machine Synchronous motors
are the most commonly used type of motor for electric propulsion
Most of the motors have double winding Power factor can be adjusted
to 1 New type of permanent magnet motors are becoming common The
power factor can be adjusted to unity by using a proper field
excitation current relative to the load Synchronous motors are
started by a converter, as an asynchronous motor or by a pony motor
(the pony motor brings the rotor at the synchronous speed where the
excitation can be switched on) Synchronous machines are generally
used as alternators. Rotating machines Synchronous machine
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December 2009 Synchronous machine with slip rings Rotating machines
Synchronous machine
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December 2009 Excitation of synchronous machine Rotating machines
Synchronous machine
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December 2009 Synchronous machine without slip rings A B C ROTOR
STATOR N S DC SUPPLY Rotating machines Synchronous machine
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December 2009 Synchronous machine inside a POD Rotating machines
Synchronous machine
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December 2009 Diesel alternator Diesel engine (speed regulation)
IeIe + - NSNS Exciter (voltage regulation) Synchronous machine
Rotating machines Synchronous machine
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December 2009 Synchronous alternator The active power (mechanical
power) comes from the diesel engine. Reactive power comes from the
exciter. Cos (phi) is defined by the network. Precautions are to be
taken to connect alternators in parallel (same voltage, same
frequency, same phase) Rotating machines Synchronous machine
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DC MOTOR
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December 2009 DC machine Advantages Easy to control Good speed
variation Reversal and high torque at low speed Disadvantages Power
limitation (10 MW) Higher volume and mass Higher construction cost
Higher maintenance cost because of the brushes Rotating machines DC
machine
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December 2009 DC Motor Based on Laplaces forces: a conductor
crossed by a current and place in a magnetic field is submitted to
Laplaces forces 1 2 3 4 4 3 2 1 B B F F Rotating machines DC
machine
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December 2009 DC machine Brushes Slip rings Rotating machines DC
machine
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TESTING OF ROTATING MACHINE
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48 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Tests of rotating machine : procedure The
manufacturer is to issue a test report giving information
concerning technical data relevant to the machine. This document is
to be provided to the society for machines for essential services.
For other machine, the test report is to be made available upon
request of BV All machines of 100 kW and over, intended for
essential services, are to be surveyed by BV and if appropriate
during manufacturing. Rotating machines Testing
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49 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Type tests and routine tests Rotating machines
Testing
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December 2009 Overspeed test For AC machines, 1.2 times the maximum
rated speed. The duration is 2 minutes. The test is satisfactory if
no permanent abnormal deformation is apparent subsequently and no
other weakness is detected. After the test, the rotor windings are
to comply with the required dielectric test. Rotating machines
Testing
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December 2009 Withstand voltage test : Withstand voltage test shall
be carried out immediately after the thermal test (when carried
out) Test to be applied between the windings under test and the
frame of the machine (core and windings not under test connected to
the frame). Machine of less than 1 kW to be tested at 500 V + 2 x
U. Machine of more than 1kW to be tested at 1000 V + 2 x U. The
full voltage is to be maintained for 1 minute. In case of second
test, the test voltage shall be 80 % of the voltage specified above
Partially rewound windings are to be tested at 75 % of the test
voltage for a new machine Rotating machines Testing
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52 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Occasional excess current A current in excess of the
rated current will result in increased temperature. The heating
effect varies approximately as the product of the time and the
square of the current. AC generators having rated outputs not
exceeding 1200 MVA shall be capable of withstanding a current equal
to 1.5 times the rated current for not less than 30s. Polyphase
motors having rated outputs not exceeding 315 kW and rated at
voltages not exceeding 1 kV shall be capable of withstanding a
current equal to 1.5 times the rated current for not less than 2
minutes. For polyphase motors having rated outputs exceeding 315 kW
and for all single phase motor, no occasional excess current test
is specified Rotating machines Testing
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53 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Momentary excess torque for motors Polyphase
induction motor : it shall be capable of withstanding an excess
torque of at least 60 % of the rated torque for 15 s, without
stalling or abrupt change of speed (voltage and frequency at their
rated value). For wound motor, the torque excess is 35 %. Polyphase
synchronous motor : it shall be capable of withstanding an excess
torque without falling out of the synchronism. The excess of torque
depends on the technology of the rotor. Unless otherwise agreed,
the excess of torque is 35 % for a cylindrical rotor and 50 % for a
salient rotor (duration of 15 s) Rotating machines Testing
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December 2009 Temperature rise test The temperature rise of a part
of a machine is the difference between the temperature of that
part, measured by the appropriate method and the temperature of the
coolant. For propulsion motor, is necessary to consider the
supplementary thermal losses induced by harmonic currents in the
stator winding (to be checked during sea trials) Rotating machines
Testing
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55 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Methods of measurements of temperature Resistance
method : the temperature of the windings is determined from the
increase of resistance of the windings. Embedded temperature
detector (ETD) method : the temperature is determined by means of
temperature detectors (e.g. Resistance thermometers,
thermocouples,...) built into the machine during construction, at
point which are inaccessible after the machine is completed.
Thermometer method : the temperature is determined by thermometers
applied to accessible surfaces of the completed machine.
Thermometers include bulb thermometers, non-embedded thermocouples,
resistance thermometers. Rotating machines Testing
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December 2009 Cooling : Cooling mediums are based on air, hydrogen,
water, . Cooling systems are based on a primary coolant and (if
any) a secondary coolant Primary coolant : a medium which removes
heat from parts of a machine Secondary coolant : a medium which
removes heat given up by the primary coolant by means of a heat
exchanger or through the external surface of the machine The method
of cooling can be either direct or indirect Direct cooled winding :
winding cooled by coolant flowing in direct contact with the cooled
part (through hollow conductors, tubes, ducts, .) Indirect cooled
winding : any other winding cooling than a direct cooled winding
Rotating machines Testing
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December 2009 Ducts (direct cooled winding) Rotating machines
Testing
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December 2009 Temperature rise limits (BV rules, ambient
temperature of 45C) : Rotating machines Testing
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December 2009 Reference coolant from IEC Temperature of the ambient
air is not considered Cooling through the external surface of the
machine Rotating machines Testing
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December 2009 Temperature rise limits from IEC (indirect) Rotating
machines Testing
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December 2009 Temperature rise calculation : Most of the high
powered motors (thrusters, propulsion motors) are based on an air /
water indirect cooling system. Example of a thruster : 1.5 Mw,
class F, air / water indirect cooling system, water temperature at
37C t=105+15-(37-25)=108C Rotating machines Testing
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December 2009 Indirect test method for synchronous machines
Rotating machines Testing
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December 2009 Verification of steady short circuit current : Under
steady short circuit condition, the generator is to be capable of
maintaining, without sustaining any damage, a current of at least
three times the rated current for a duration of at least 2 s (or
any time delay which may be fitted in a tripping device). Rotating
machines Testing
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December 2009 Load impact for alternators : According to IEC
6092-301, governors shall be such that they will maintain the speed
within a momentary variation of 10 % and a permanent variation not
exceeding 5 % when the rated load is suddenly thrown off and when
50 % load is suddenly thrown on, followed after a short instant by
the remaining 50 % load. The application of load in more than 2
steps is permitted in some cases. The recovery time is to be less
than 5 seconds. IEC 60092-301 also defines voltage variations when
a load equivalent to 60 % of the rated current (or maximum load on
board) is applied (85% to 120 % of the nominal voltage, with a
restoration within + / - 3% in not more than 1.5 seconds).
Requirements are different for emergency sets (+ / - 5 % in not
more than 5 seconds). Rotating machines Testing
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December 2009 Loads on alternators running in parallel : For a.c.
generating sets operating in parallel, the governing
characteristics of the prime movers are to be such that, within the
limits of 20% and 100% total load, the load on any generating set
will not normally differ from its proportionate share of the total
load by more than 15% of the rated power in kW of the largest
machine or 25% of the rated power in kW of the individual machine
in question, whichever is the lesser. When a.c. generators are
operated in parallel, the reactive loads of the individual
generating sets are not to differ from their proportionate share of
the total reactive load by more than 10% of the rated reactive
power of the largest machine, or 25% of that of the smallest
machine, whichever is the lesser. Rotating machines Testing
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December 2009 Specific test for high voltage rotating machine A
frequency high voltage test is to be done on the individual coils.
This test is to be done on the coils after they have been inserted
in the slots. The purpose is to verified that the coils have not
been damaged during the insertion. Due to the various technologies
involved, no general requirements can be specified for the test
values Rotating machines Testing
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REQUIREMENTS FOR ROTATING MACHINES
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December 2009 Rotating machines REQUIREMENTS Classification Rules
requirements to be studied
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3 Transformers and requirements
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Transformers principles
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December 2009 Working principle A transformer is an electrical
device that transfers energy from one electrical circuit to another
one by magnetic coupling but without any moving parts. Transformer
consists in two windings (or coils) with the exception of
autotransformers. Primary winding is fed by alternating current
which produces changing magnetic field. Secondary winding which is
placed in this varying magnetic field develops alternating voltage
and a current when the secondary side is connected to a load (A
transformer is a voltage generator) Transformers Principles
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December 2009 Two separate windings transformer Electric diagram V1
I1 V2 I2 V2 V1 n2 n1 I1 I2 n2 n1 Primary winding Secondary winding
Magnetic circuit Transformers Principles
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December 2009 Generalities As energy is transfer by magnetic
coupling transformer provides a galvanic isolation. Ratio of
voltage between primary and secondary windings is just ratio in
turn of the two windings V 2 = (N 2 /N 1 )V 1 Set down and set up
voltage transformer used the same principle Power delivered by a
transformer cannot exceed the power fed into it. Efficiency of
transformers is about 98%. Transformers Principles
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December 2009 V2 V1 n2 n1 I1 I2 V1 I1 V2 I2 n2 n1 Transformers,
except those for motor starting, are to be double wound (two or
more separate windings). Auto-transformer Common winding
transformer Electric diagram Transformers Principles
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December 2009 Current transformer Electric diagram Used for
measurement of current in high voltage installation Transformers
Principles
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December 2009 V1 I10 L1 n2n2 n1n1 n2n2 n1n1 I2 I1 I2 V2 Rf I1F I1V
Rs V1 n2n2 n1n1 Ls V2 V1 n2 n1 I1 I2 Equation - Formulas Electric
diagram Transformers Principles
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December 2009 2 B = n1 S V1 B saturation e=d /dt B or I Saturation
Saturation Limit of use Saturation curve Transformers
Principles
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December 2009 Magnetic circuit - principle The lines of the
magnetic field pattern run through the coil, spread out from the
end and go round the outside and in at the other end (Fig 1). The
purpose of the magnetic circuit is to concentrate the magnetic
field, to avoid flux leakages (Fig 2). Fig. 1Fig. 2 Transformers
Principles
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December 2009 Magnetic circuit - principle As magnetic circuit is a
conductor, voltage will generate induced wasteful currents (called
Eddy current) causing resistive heating of the core. To limit these
currents, magnetic circuit is to be poor conductor. So it is made
of steel laminations made of thin insulated (varnish) iron sheets
clamped together. Transformers Principles
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December 2009 Arrangement of transformers Diagram showing windings
and magnetic circuit Primary winding Secondary winding Single Phase
Transformer Three Phases Transformer Magnetic circuit Phase 1 Phase
2 Phase 3 Transformers Principles
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December 2009 Manufacturing of transformer Picture of magnetic
circuit Transformers Principles
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December 2009 Manufacturing of transformer Picture of windings
Transformers Principles
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December 2009 Manufacturing of transformer Picture of windings
before impregnation Transformers Principles
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December 2009 Manufacturing of transformer Picture of dry type
transformer Transformers Principles
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December 2009 Manufacturing of transformer Picture of connection
heads of a dry type transformer Transformers Principles
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Transformers main parameters
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December 2009 Type - Dry type Pictures of dry type transformer
Transformers Main parameters
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December 2009 Type - Oil immersed Pictures of oil immersed
transformer (sealed/hermetic type) -Drain valve -Drip tray for
collecting oil leakages -Non-toxic oil and not supporting
combustion -Gas-actuated protection device Transformers Main
parameters
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December 2009 Type - Oil immersed Oil immersed transformer
(breathing type) Conservator Transformers Main parameters
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December 2009 Type - Oil immersed Pictures of oil immersed
transformer (breathing type) - Design to prevent risk of spilling
liquid when inclined - Provision for breathing (suitable
dehydrator) Transformer installed aboard Queen Mary 2 Transformers
Main parameters
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December 2009 Time index : phase displacement between primary side
and secondary side (important for transformers working in
parallel). The phase displacement is usually expressed by using a
clock-hour figure. In this example low voltage vector lagging the
high voltage vector by an phase angle of 30 Coupling Dy 11 coupling
A B C b c a 0 11 Dy11 a bc A B C LV side HV side n 12 3 6 9
Transformers Main parameters
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December 2009 Coupling Other possible couplings Transformers Main
parameters
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December 2009 I 2N I 1N U %. U N12 U %. U N23 U %. U N13
Short-circuit characteristics Definition of Ucc Ucc is the
percentage of the primary voltage that produces the nominal current
when the secondary side of the transformer is short circuited.
Short-circuit impedance of a transformer Z T = U CC. U S N U : No
load phase-to-phase voltage S N : Transformer kVA rating For
information : Transformer of 630 kVA U CC = 4% Transformer of 2500
kVA U CC = 6% Transformers Main parameters
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December 2009 V1 I1 V2 I2 Z2 E2 + n1 n2 Transformer impedance
Voltage on secondary side to be adjusted when transformer is loaded
(tapping points: -5%, -2.5%, 0, +2.5%, +5%). Transformers Main
parameters
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December 2009 Manufacturer plate Example 1: Transformers Main
parameters
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December 2009 Manufacturer plate Example 2: Transformers Main
parameters
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Transformers requirements
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December 2009 Design of transformers (BV rules) Transformers,
except those for motor starting, are to be double wound (two or
more separate windings). Transformers are normally to be of the dry
type. When a forced air cooling system is used, an alarm is to be
activated in the event of its failure. Liquid-cooled transformers
are accepted with some conditions (non toxic liquid, temperature
and pressure alarm, liquid gauge,....). Transformers
Requirements
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December 2009 System design with transformer (BV rules) Where
transformers, converters or similar appliances constitute an
essential part of the electrical supply system, the system is to be
so arranged as to ensure a continuity of supply. This may be
achieved by arranging at least two three-phase or three
single-phase transformers At the secondary side: Delta connection
or star connection with a spare part. Each transformer required is
to be located as a separate unit with separate enclosure or
equivalent, and is to be served by separate circuits on the primary
and secondary sides. Suitable interlocks or a warning label are to
be provided in order to prevent maintenance or repair of one
single-phase transformer unless both switchgears are opened on
their primary and secondary sides. Transformers Requirements
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December 2009 System design with transformer (BV rules)
Transformers Requirements
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December 2009 Primary side Secondary side Three single-phase
transformers Arrangement diagram Transformers Requirements
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December 2009 Transformers working in parallel The voltage ratio
are to be identical. The time index are to be identical. The Ucc%
are to be identical (ratio between 0.9 and 1.1) Provisions are to
be provided to trip the switch on secondary winding side when the
corresponding switch on the primary side is open. Transformers
Requirements
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December 2009 Transformer working in parallel 630 kVA 400V / 230V
Dyn11 Ucc: 6% I 400 V 230 V 630 kVA 400V / 230V Dyn11 Ucc: 6% I
Transformers Requirements
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December 2009 Generalities The tests and, if appropriate,
manufacture of transformers of 100 kVA and over (60 kVA when single
phase) intended for essential services are to be attended by a
Surveyor of the Society. Transformers of 5 kVA up to the limit
specified above are approved on a case by case basis, at the
discretion of the Society, subject to the submission of adequate
documentation and routine tests. Transformers Requirements
Slide 105
105 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Document to be submitted For the case by case
certification of power transformers, following documents are to be
submitted to LPO for examination. Drawings are to be approved and
all comments cleared before inspection at works. Technical data
sheet General arrangement/main dimensions diagram Auxilaries
connection diagram (e.g. temperature sensors, protection device for
oil immersed type transformer) Test procedure For transformer with
a forced cooling system Cooling circuit arrangement + BV
certificate of main auxiliaries (heat exchanger, electrical motor
of pump) For breathing transformers Justifications that precautions
have been considered to prevent oil spillages Transformers
Requirements
Slide 106
106 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Test of transformers On new transformers intended for
essential services tests are to be carried out. The manufacturer is
to issue a test report giving technical information and the results
of the tests required. Such test reports are to be made available
to the Society. In the case of transformers which are completely
identical in rating and in all other constructional details, it
will be acceptable for the temperature rise test to be performed on
only one transformer. Transformers Requirements
Slide 107
107 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 High voltage test Transformers are to be subjected to
a high voltage test. Test intended to verify the AC withstand
strength of the line and neutral terminals and their connected
windings to earth and other windings. The r.m.s value of the test
voltage defined by BV rules is to be equal to 2 x U + 1000 (minimum
2500 V). Repeated dielectric tests are to be carried at 80% of the
test voltage required for new machine. IEC 60076 requires to test
the low voltage transformer at 3000 V. For high voltage
transformer, BV rules refer to IEC 60076 (for a 6.6 kV transformer,
the test voltage is 20 kV). Full voltage is to be maintained for 1
minute. Test is successful if no collapse of the test voltage
occurs. Transformers Requirements
Slide 108
108 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 High voltage test Test description Repeated
dielectric: For transformers which have been already been in
service and have been refurbished or serviced, the dielectric test
shall be repeated at test levels of 80 %. Transformers
Requirements
Slide 109
109 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Induced voltage test Test intended to verify the
insulation between windings and between phases. Weakness in
dielectric design during manufacturing may cause partial discharge
activity during induced voltage test. Internal insulation is to be
checked by applying 2 times the rated voltage of the transformers.
In order not to exceed the usual induction, this test can be made
with a voltage source having a frequency of at least twice the
rated frequency. The test time at full test voltage is to be 1
minute for any test frequency up to 2 x F rated. When the test
frequency exceeds twice the rated frequency, the test time can be
reduced to 120 x F rated / F test (but not less than 15 sec).
Transformers Requirements
Slide 110
110 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Induced voltage test Test description VV U TEST = U N
x 2 Duration of test : (at least 15 s) 120 x F N F TEST
Transformers Requirements
Slide 111
111 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Temperature rise test Transformers are to be
submitted to a test under the rated load current. This test is to
last long enough for temperature stabilising (2 K per hour). The
permissible limits of temperature rise with an ambient air
temperature of 45C for (natural or forced) air-cooled transformers
are given next page. The temperature rises shown for windings refer
to measurement by the resistance method while those for the core
refer to the thermometer method. Transformers Requirements
Slide 112
112 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 I 2N I 1N U % xU N12 U % xU N23 U % xU N13 U 12 U 23
U N13 Temperature rise test The test is to be carried out at rated
power. The test can also be split in 2 parts : nominal voltage and
nominal current. The temperature rise is then calculated.
Transformers Requirements
Slide 113
113 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009 Classification Rules requirements to be studied
Transformers Requirements
Slide 114
114 Bureau Veritas S.A. internal use only BVN TM ELEC3 V0
December 2009