2. What are electrical machines?What are its types?
In electrical engineering, electric machine is a general term
for machines using electromagnetic forces, such as electric motors, electric
generators, and others. They are electromechanical energy converters: an
electric motor converts electricity to mechanical power while an electric
generator converts mechanical power to electricity. The moving parts in a
machine can be rotating (rotating machines) or linear (linear machines).
Besides motors and generators, a third category often included is transformers,
which although they do not have any moving parts are also energy converters,
changing the voltage level of an alternating current.
How popular are they?
The industrial sector, in developed countries, uses more than 30% of the
electrical energy. More than 60% of the electrical energy is consumed by
electric motor drives
Why do we need advancements in them?
Replacing all distribution transformers by energy efficient types could save
200 TWh a year, equivalent to 130 million tonnes of CO2 emissions. An advantage
large enough to justify the effort.
4. History of transformers:
In 1831,Faraday's first transformer: Twocoilswound
on an irontoroid
The Next Fifty Years,1832-1882
Henry's Coils:
5. Zipernowski-Deri transformer: One of the bestof
the early ring-shaped transformer was presented
by Messrs Karoly Zipernowski and Miksa Deri in
1885.
First Transformers with closed
circuit: shows the core type
transformer developed by Gaulard
and Gibbs and used byWestinghouse
in 1885.
6. Aspects that can be considered as
advancement in the transformer:
Design modelling
Material used
Added features
Manufacturing methodologies
7. Modern Trends in Design,
Modelling, and Analysis of the Core
The performance parameters of thecoredepend on
both its material anddesign.
Thedesign of thecore-jointsand corners has a
significant impact on itsperformance.
An accurate prediction of nonlinear, hysteretic,and
dynamic core characteristics and their numerical
implementation is still a challenging task to the
researchers.
8. The field equation in two-dimensional (2-D)
problems using magnetic vector potential
formulation can be written as
An Finite Element Method modelling of the core with its
nonlinear, hystereticand dynamiccharacteristics is given:
Geometric FEM model Flux linesplot Dynamichysteresis
loop at pointP
9. Effects of Manufacturing Practices on the Core
Performance:
Handling process
Handling cutting and slitting:
•Core materials are very sensitive to manufacturing processes such as
handling, cutting and slitting. They should be handled with care during
storing and processing; elasticand plasticstressescan be induced and the
losses will behigher.
•Stressesare induced adjacent toedges byslitting, shearing and stamping
operations .
Slitting process
10. Use of inner peripheral guard plate
Corecoil handling (a) with innerguard plate (b) without
inner guard plate
The present case study shows the effect of handing process on
CRGO materials. The loss increases while the inner peripheral
guard plate is not used to keep coils of CRGO laminations.
11. The losses measured using Single Sheet Tester (SST) in
two cases with and without inner peripheral guard plate
as shown in Figs. (a) and (b), respectively. The results are
given table-I for the two above mentioned cases for core
material (M5, 0.3mm).
12. Effect of Surface Insulation on No-
load Losses
Core materials (a) with lower SIR value (8 ohm-cm2) (b)
with higher SIR value (60ohm-cm2)
The no-load test of two core materials with different surface insulation
resistance (SIR) values is performed. Thecore lossesare higher in thecaseof
thecore material with lowersurface insulation resistance.
13. The higher losses in case of lower surface insulation resistance can be
attributed to occurrence of short-circuit on its surface. The results have been
observed fora 400 kVAdistribution transformercore. Twocore materialswith
lower and higher SIR values are shown in Figs. 5(a) and 5(b), respectively. The
results have been given in tableII.
14. Transformer With ABB BIOTEMP
Dielectric Insulating Fluid.
Disadvantages of typically used mineraloil.
Highly inflammable.
Environmental contamination.
Poor moisture tolerance.
.
15. Characteristics of BIOTEMP
BIOTEMP is made from high-oleicoils, such as sunflower,
containing
more than 75 percent mono-unsaturated fattyacids.
97% biodegradable within 21days.
BIOTEMP is an inhibitedoil.
BIOTEMP is verified as abiodegradable.
BIOTEMP exhibits excellent dielectric characteristics with
high temperaturestabilityand flash and fire resistanceof
330°C and 360°C, respectively, compared with 145°C and
160°C for mineraloil.
‘less flammable’ and less hazardous.
BIOTEMP is not affected by reactionswith other materials.
High capacity of absorption.
16. Advancement in conservator tank
A conservator tank of transformer provides adequate space to this
expanded transformeroil. Italsoacts as a reservoirfortransformer
insulating oil.
Thereare two types of conservatortank
• Atmoseal TypeConservator
• Diaphragm Sealed Conservator
17. 1. Atmoseal TypeConservator
In this type conservator of transformer, an air cell made of NBR
material is fitted inside the conservator reservoir. The silica gel
breatheris connected at the topof thisaircell.
18. 2. Diaphragm Sealed Conservator
Herediaphragm is used as a barrierbetween transformeroil and
atmosphericair
19. Self-dehydrating air breather(SDB)
– No silica gel salt maintenance required
– Continuous and safer control and monitoring ofthe
silicagel salt hydration as well as regeneration
20. Main Benefits for End Userare:
Increase transformerreliability
Continuous moisture absorption ensured by two
independant silicagel tanks workingalternatively.
Operational costsavings
Automatic silicagel regeneration processdrastically
reduce expensive maintenanceactivities
Easy toinstall
Suitable for new installationand retrofit
case.
21. Dry Type Transformer
Dry type transformer never uses any
insulating liquid where its winding with core be
immerged. Ratherwindingswith coreare kept
within a sealed tank that is pressurized withair.
Type of Dry TypeTransformer.
Thedry type transformer is of two types.
1. They areCast Resin DryType Transformer ( CRT)
2. Vacuum pressure Impregnated Transformer (VPI)
23. Advantages of Dry TypeTransformer
The main advantages of dry type transformer are given
Below.
Safety for people and property.
Maintenance and pollution-freesolution.
Easy installation.
Side clearance isless.
Environmentally friendly.
Excellent capacity to supportoverloads.
Reduced cost on civil installationworks and fire protection
systems.
Excellent performance in caseof seismicevents.
No fire hazard.
Excellentresistance toshortcircuitcurrents.
Long lasting due to low thermaland dielectric heating.
Suited for damp and contaminatedareas.
24. Disadvantages of Dry TypeTransformer:
But there are some disadvantages of dry type transformer. They are-Dry
type transformer is long lasting and with less chance of winding failure.
But once it fails whole set up is to changed, i.e. complete change of high
voltageand lowvoltagewinding with limb.
For same power and voltage rating, dry type transformer is costlier than
oil cooled transformer.
Application of Dry TypeTransformer:
Dry type transformerarewidely used in-Chemical, oil and gas industry
Environmentallysensitiveareas (e.g. waterprotection areas)
Fire-risk areas (e.g. forests)
Inner-citysubstations
Indoor and undergroundsubstations
Renewable generation (e.g. off-shore windturbines)
25. Nitrogen Injection Fire Prevention and Extinguishing
System for Oil Filled Transformers
The “Nitrogen injection and drain method” is one of the best fire
prevention and extinguishing system for oil filled transformers for
indoor/outdooruse. This system is fullyautomaticand unattended,
Maintenance freeand lowcostcompare toothersystems.
26. Advantage of Nitrogen Injection & Drain Method of FireProtection
Low investmentcostas compared tootherconventional system.
Very low post fireand nosecondarydamages.
Minimum maintenance and runningcost.
No climaticeffects.
Suitable for indoor/ outdoorinstallation.
Minimum spacerequirement.
Multi signals foractivation, eliminates false alarms.
Allows system testing on operational transformernot possible
with conventional firesystem.
No moistureabsorbing in inside the transformerdue topresence of.
nitrogen.
Greatsaving in cost, due toabsenceof moisture.
Fullyautomatic, unattended and a fool proof system.
Itcan beoperated manually / automatically, local / remotecontrol.
Nowaterreservoiror majorcivil work required.
Prevents transformerexplosionensuring system remains functioning.
Prevention of unplannedoutages.
Considerablesavings.
Improves overall power systemreliability.
27. Gas insulated
transformers (GITs)
• SF6 gas is used as insulation
media with relatively low gas
pressure.
• Top gas temperature limit of 110 C
instead of the maximum
conventional 95 C top oil
temperature for oil-immersed
transformers.
• GIT have the following
advantageous:
• Non-inflammable and
nonexplosive.
• Moisture resistant and dust
resistant.
• Clean as there are no
contaminations to surroundings
since these transformers are
sealed with non-poisonous,
odourless SF6 gas, even if the SF6
gas leaks unlike mineral oil-
immersed transformers.
28. Core
Materials
Early cores were made from bundles of soft-iron wire.
The first transformers manufactures in the 1880s had
cores made from high grade wrought iron.
Cold rolled grain oriented steels (CRGO).
High permeability grain oriented silicon sheet steels.
Laser irradiated super oriented steels.
Amorphous steels.
29. Developments in terms of
manufacturing
• Power transformers make use of grain orientated steel materials
for the core.
• Developments are ongoing and moving towards even thinner
material thickness (from 0,23 mm to 0,18 mm) to reduce losses.
• Laser scribing of decreases the eddy current losses by refining
the magnetic domains in the steel. Stresses are introduced in the
rolling and coating processes, which increase the losses in the
material, by affecting the grain boundaries and domains.
• Coating is applied to reduce eddy currents. Laser scribing of lines
in the direction of the grain orientation reduces the stresses and
improves the grain boundaries.
30. Amorphous core transformers
Further increase in transformer efficiency is possible to reach by replacement silicon steel
cores with new types of magnetic core materials, e.g. amorphous ribbons. These materials
are produced by rapid solidification of a liquid alloy, what gives specific magnetic properties,
especially very low energy loss
Amorphous cores are usually produced as wounded, one-side cutting ones, due to
mechanical properties of amorphous ribbons to add text
This solution ensures the correct location of air gaps inside a core and simplifies electric
windings assembling
The cross-section of amorphous cores is larger in comparison to silicon steel ones, due to
lower saturation induction of amorphous ribbons
31. The multiple step lap (MSL) configuration, where overlap occurs at multiple different
positions, has been developed to reduce reluctance even further. This leads to a higher
manufacturing cost offset by savings in losses.
32. Digital
transformers
• With multiple generators, prosumers and
decentralised generation sources, the grid
needs to handle power flows in different
directions, 24×7
• Energy utilities are responding to these
challenges by adopting digital technologies
with the aim of helping users get
actionable information and insights that
enable better decision-making and asset
management
• Transformers are the immediate candidates
for the integration of digital and smart grid
technologies
33.
34. • Digital transformer solutions largely have three blocks – hardware,
software and services – that work seamlessly to deliver reliability,
efficiency and future-readiness to utilities.
• Built-in components like digital sensors, dissolved gas analysers and
digital safety devices collect data for monitoring, diagnostics and
control at the local level.
• The same data can also be monitored and used for control, and
preventive and predictive maintenance at the station control level via
the cloud
• Submersible transformer inspection robots are making inroads in the
market. These wireless robots can be manueuvred through a liquid-
filled power transformer to perform fast, safe and cost-effective
internal inspection, which can be shared remotely, in close to real time,
with experts
• New digital transformers also address customers’ cybersecurity
concerns
• The traditional cooling controls of power transformers are moving
towards digitisation
35. Micro gas sensors
• Nano structures have proved
capable of detecting and measuring
gases dissolved in transformer oil
such as hydrogen and methane, both
of which are indicative of failure.
• The absorption of hydrogen by
palladium alloy nanoparticles-based
sensor for the detection of hydrogen
gas dissolved in power transformer
oil results in changes in the sensor’s
physical, electrical and optical
properties.
• The sensor, which was tested for
different hydrogen concentrations at
different temperatures in
transformer oil, exhibited suitable
sensitivity and short reaction time.
36. Use of Nanotechnology
in transformers
• Addition of nano particles to the oil has
been proposed as a means of
improving the heat transfer and
resistivity.
• Use of nanotechnology to manufacture
micro gas detectors, which can be
placed permanently in the oil, is also
being developed.
• The addition of nanoparticles at a
concentration of up to 8% increased
the heat transfer capabilities of mineral
oil by up to 80%. The nano structure
used was Hexagonal boron nitride (h-
BN) particles, about 600 nm wide and
up to five atomic layers thick. There
was no change to the mechanical
properties of the oil.
This Photo by Unknown author is licensed under CC BY-SA-NC.
38. What are motors?
• An electric motor is an electrical machine that
converts electrical energy into mechanical energy.
Most electric motors operate through the
interaction between the motor's magnetic
field and electric current in a wire winding to
generate force in the form of rotation of a shaft.
Electric motors can be powered by direct
current (DC) sources, such as from batteries,
motor vehicles or rectifiers, or by alternating
current (AC) sources, such as a power
grid, inverters or electrical generators. An electric
generator is mechanically identical to an electric
motor, but operates in the reverse direction,
converting mechanical energy into electrical
energy.
39. PROGRESS IN
ELECTRIC
MOTORS
TECHNOLOGY
• Electric motors are the most
popular machines of
everyday life and the number
of their types increases with
the development of science
and technology.
• Examples are SRMs,
piezoelectric motors,
transverse flux motors,
written pole motors, various
hybrid motors, smart motors,
linear motors.
• Impact of power electronics:
variable speed drives,
switched reluctance motor
drives impact of new control
strategies: self tuning
electromechanical drives,
‘intelligent’ drives ,fuzzy
control, senserless control.
40. Contd.
• new areas of applications e.g.
robotics, electric cars ,
aerospace, vacuum, high
pressure liquids , harsh
environment, nuclear
technology, mechatronics,
microelectromechanical
systems(MEMS)
41. MATERIAL
ENGINEERING
• Owing to the invention of high
energy SmCo PM magnets in the
1960s and NdFeB in the 1980s, a
revolutionary progress has been
made in construction of high
efficiency and high power density
PM machines
• No electrical energy is absorbed
by the excitation system and thus
there are no excitation losses
• Higher torque or output power
per volume than when using
electromagnetic excitation,
42. Soft magnetic powder composites
• New soft powder
materials which
are competitive to
traditional steel
laminations have
recently been
developed
• Powder materials
are recommended
for 3D magnetic
circuits e.g. claw-
pole, transverse
flux and disk type
motors.
43. High saturation ferromagnetic
alloys
• Cobalt-iron alloys have the highest
known saturation magnetic flux
density, about 2.4 T. They are the
natural choice for applications where
mass and space saving are of prime
importance
• The nominal composition e.g. for
HiSat50 is up to 50% cobalt, 2%
vanadium and the rest is iron.
44. Present status of
electrical motors
A.c. motors
• Cage induction motors
have been the most
popular electric motors in
the 20th century.
• Recently, owing to the
dynamic progress made in
the field of
power electronics and
control technology, their
application to
electromechanical drives
has increased.
• The rated output power
ranges from 70 W to 500
kW, with 75% of them
designed with four pole
stators.
45. Disadvantages
Over 10% of applications
use some type of electronic
controller either in the form
of solid state soft starters or
frequency inverters.
• small air gap
• the torque
proportional to
the voltage
squared
• the possibility of
cracking the
rotor bars due to
hot spots at
plugging and
• lower efficiency
and power factor
than those of
synchronous
motors.
46. Synchronous motors
• Synchronous motors have several advantages
in Comparison with induction motors such as
controllable,
• Power factor, proportionality between the torque, and
• Input voltage,
• Speed dependent only on the input Frequency and
number of poles,
• Larger air gap, and
• Better adaptation to pulsating load torque than
induction motors.
47. Contd.
• Synchronous motors
can operate with unity
power factor and even
deliver the reactive
power to the supply
system (power factor
correction).
• Synchronous motors
with PM excitation are
the most efficient.
• Have the highest
power density.
• Disadvantage
• Drawback is much
higher price
48. Brushless PM motors
• Rare earth PMs improve the output
power-to-mass ratio, efficiency,
dynamic performance, and reliability.
• A brushless PM motor has the magnets
mounted on the rotor and the
armature winding mounted on the
stator.
• In PM brushless motors the power
losses are practically all in the stator
where heat can be easily transferred
through the ribbed frame or, in
larger machines, water cooling systems
can be used.
• In a hybrid brushless PM motor an
auxiliary d.c. field winding helps to
increase the speed range over
constant power region.
49. Stepping Motors
• The stepping motor is a singly-excited motor converting
electric pulses into angular displacements.
• It has salient poles both on the stator and rotor
and polyphase stator winding.
• A two-phase hybrid stepping motor performing 200
steps per revolution is nowadays a popular motor in
factory automation systems.
• Very High resolution can be achieved.
• Micro-stepping mode in which the basic motor step
is Subdivided by proportioning the current in the two
phase Winding.
50. Switched Reluctance Motors
• The SRM is a polyphase
doubly-salient electric motor
with no winding and no
excitation system on the rotor.
• The electromagnetic torque is
very sensitive to the turn-on
angle and turn-off angle of the
stator phase current.
• Thus, the SRM controller
requires information about
the rotor position.
• Needs rotor position sensors.
• Have perspectives of
applications in energy efficient
drives, high speed drives or
fault tolerant drives.
51. • Power electronics
converters for SRMs are
similar to inverters;
however, the switching
frequency is lower and
current sharing between
solid state devices is
better.
52. Servo motors
• Servo motor technology has changed in recent years
from conventional d.c. or two-phase a.c. servo motor
drives to new maintenance-free brushless three
phase vector-controlled a.c. drives for all motor
applications
53. PM transverse flux
motor
• Transverse flux machines have shorter flux
paths than traditional longitudinal flux
machines.
• Torque and power density is high.
• Has a toroidal armature winding
embraced by U shaped ferromagnetic
cores.
• Motors are high torque and power density,
simple stator winding consisting of a single
ring-shaped coil.
• Modular construction.
• The more the poles the less the torque
pulsation.
• The stator core uses large number of
“transverse flux” magnetic circuits and
good quality powders materials to make
the construction economical.
54. PM disc type
motors
• Disc type or axial flux motors
provide better heat transfer
and allow for higher line
current densities than
standard cylindrical motors.
• Direct water cooling system
and hollow armature
conductors can provide the
most efficient heat transfer.
• Disc type motors can totally be
iron free motors provided that
PMs are arranged such.
55. WRITTEN POLE
MOTORS
• A written pole motor has a special
coil that `writes’ poles onto a ring of
magnetic material attached to the
Rotor.
• The number of poles and their
positions can be
• Continuously varied while the
machine in operating
• Since the starting current is only
about 30% of that of an equivalent
cage induction motor, a written pole
motor can start directly with high
inertia load without any solid state
starter.
• Written pole motors and generators
can be used very effectively as
machines integrated with flywheel
energy storage systems
56. PIEZOELECTRIC
MOTORS
• Piezoelectric motors, also called ultrasonic motors
operate on the principle of piezoelectric effect which
produces mechanical vibrations in the ultrasonic range.
• The most popular motors are travelling wave
piezoelectric motors, invented in Japan in 1982.
• Stator has electrodes arranged in two-phase
configuration and is fed from a two phase inverter at the
frequency above 20 kHz (not audible).
• The rotor turns in the opposite direction to the
travelling wave due to friction between the stator and
rotor.
• Typical applications include auto-focus lenses,
timepieces, window blinds, x-y positioning stages,
robotics, automobile industry and consumer goods.
57. References :
• IEEE
• SPRINGER
• WIKIPEDIA
• RECENT DEVELOPMENTS IN ELECTRICAL MOTORS AND
DRIVES Jacek F. Gieras* Izabella A. Gieras**e-mail:
jgieras@snet.net e-mail: igieras@bsc-rscservices.com*United
Technologies Research Center, East Hartford, CT, U.S.A.**
Beaumont Services Company, Royal Oak, MI ,U.S.A.
• Jacek F. GierasFIEEE, UTC Hamilton Sundstrand Fello Applied
Research, Rockford, Illinois, USA Proffessor of Electrical
Eng.University of Technology and Life SciencesBydgoszcz, Poland
• ELECTRICALINDIA.IN
• SCRIBD.COM
