This document provides information about synchronous machines. It discusses:
- Synchronous generators are used to generate electrical power from steam, gas, or hydraulic turbines. They are the primary source of power generation.
- Synchronous machines can operate as generators or motors. Large synchronous motors are commonly used for constant speed industrial drives.
- The document describes the construction, types, operation, and testing of synchronous machines. It provides equations to calculate parameters like voltage, frequency, reactance, and regulation from test data.
- Parallel operation and synchronization of generators is discussed. Concepts like the infinite bus and power-angle characteristics are introduced.
DC motors
Torque & Speed Equations
Torque -Armature current Characteristics
Speed - Armature current Characteristics
Torque-speed characteristics
Applications
Speed Control
DC motors
Torque & Speed Equations
Torque -Armature current Characteristics
Speed - Armature current Characteristics
Torque-speed characteristics
Applications
Speed Control
Part of Lecture series on EEE-413, Electrical Drives (DC Drives) delivered by me to students of VIII Semester B.E. (Electrical), Session 2018-19.
Z. H. College of Engg. & Technology, Aligarh Muslim University, Aligarh.
Missing materials will be uploaded shortly.
Please comment and feel free to ask anything related. Thanks!
Permanent Magnet Synchronous motor (PMSM) or Permanent Magnet AC motor:
Introduction to PMSM motor.
Types of PMSM Motor.
Mathematical modelling of PMSM motor.
Advantages and dis Advantages of PMSM motor
Includes Introduction, Derivation of power flow through transmission line, Single line diagram of three phase transmission, methods of finding the performance of transmission line. 1.Analytical Method 2.Graphical method (circle diagram)., circle diagram of receiving end side and sending end side.
Generalized network constants and equivalent circuits of short, medium, long transmission line. Line performance: regulation and efficiency, Ferranti effect.
Physical Description
Mathematical Model
Park's "dqo" transportation
Steady-state Analysis
phasor representation in d-q coordinates
link with network equations
Definition of "rotor angle"
Representation of Synchronous Machines in Stability Studies
neglect of stator transients
magnetic saturation
Simplified Models
Synchronous Machine Parameters
Reactive Capability Limits
Consists of two sets of windings:
3 phase armature winding on the stator distributed with centres 120° apart in space
field winding on the rotor supplied by DC
Two basic rotor structures used:
salient or projecting pole structure for hydraulic units (low speed)
round rotor structure for thermal units (high speed)
Salient poles have concentrated field windings; usually also carry damper windings on the pole face.Round rotors have solid steel rotors with distributed windings
Nearly sinusoidal space distribution of flux wave shape obtained by:
distributing stator windings and field windings in many slots (round rotor);
shaping pole faces (salient pole)
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Part of Lecture series on EEE-413, Electrical Drives (DC Drives) delivered by me to students of VIII Semester B.E. (Electrical), Session 2018-19.
Z. H. College of Engg. & Technology, Aligarh Muslim University, Aligarh.
Missing materials will be uploaded shortly.
Please comment and feel free to ask anything related. Thanks!
Permanent Magnet Synchronous motor (PMSM) or Permanent Magnet AC motor:
Introduction to PMSM motor.
Types of PMSM Motor.
Mathematical modelling of PMSM motor.
Advantages and dis Advantages of PMSM motor
Includes Introduction, Derivation of power flow through transmission line, Single line diagram of three phase transmission, methods of finding the performance of transmission line. 1.Analytical Method 2.Graphical method (circle diagram)., circle diagram of receiving end side and sending end side.
Generalized network constants and equivalent circuits of short, medium, long transmission line. Line performance: regulation and efficiency, Ferranti effect.
Physical Description
Mathematical Model
Park's "dqo" transportation
Steady-state Analysis
phasor representation in d-q coordinates
link with network equations
Definition of "rotor angle"
Representation of Synchronous Machines in Stability Studies
neglect of stator transients
magnetic saturation
Simplified Models
Synchronous Machine Parameters
Reactive Capability Limits
Consists of two sets of windings:
3 phase armature winding on the stator distributed with centres 120° apart in space
field winding on the rotor supplied by DC
Two basic rotor structures used:
salient or projecting pole structure for hydraulic units (low speed)
round rotor structure for thermal units (high speed)
Salient poles have concentrated field windings; usually also carry damper windings on the pole face.Round rotors have solid steel rotors with distributed windings
Nearly sinusoidal space distribution of flux wave shape obtained by:
distributing stator windings and field windings in many slots (round rotor);
shaping pole faces (salient pole)
Water Purifiers and RO Plant By Valency Enterprises Pvt. Ltd, Nagpur indiamartsupplier
Established in the year 2014, Valency Enterprises Pvt. Ltd. is considered amongst the praiseworthy manufacturer, supplier and service provider of an exceptional quality collection of Water Purifiers, RO Plant, RO Spare Parts, Water Chiller, DM Plant, Air Freezer, Water Softener Plant, Water Cooler, Bottling Plant, RO Repairing Service, RO Installation Service and RO AMC Service.
Practical Arc Flash Protection for Electrical Safety ProfessionalsLiving Online
Electrical safety is an important issue for those working on electrical facilities in utility networks and large industrial installations. A number of serious accidents including fatalities occur every year due to accidents involving electricity resulting in huge financial losses and wasted man-hours. Arc flashes in electrical equipment are now considered one of the major causes of electrical accidents even surpassing the well known hazards of electric shock. Avoiding arc flash incidents and the resulting injuries is one of major challenges today facing electrical workers and requires adequate attention in the stages of system planning, design, installation, operation and maintenance.
Injuries due to arc flash can depend on many factors, one of which is the incident thermal energy on a worker exposed to a flash. Today, a considerable body of knowledge exists as a result of research efforts and is available to designers and maintenance engineers in the form of standards such as IEEE 1584 and NFPA 70E. This workshop will detail the basis of this approach and also about the major advances that have been made in the area of PPE made of FR fabrics and rated for different levels of thermal exposure.
Prevention however still remains the best form of protection and switchgear manufacturers have made considerable design advances to ensure that the effect of arc flash incidents is contained within the enclosure of switchgear (often called arc flash resistant switchgear) and methods of testing such switchgear have also evolved simultaneously. Another important factor is the approach to avoid arc incidents within the switchgear by proper design and maintenance and techniques to reduce the severity of the flash should such incidents occur.
These would form the key focus areas of this workshop.
MORE INFORMATION: http://www.idc-online.com/content/practical-arc-flash-protection-electrical-safety-professionals-22
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How Reverse Osmosis Water Purification Systems WorkAlisha Roy
Reverse Osmosis is a process in which dissolved inorganic solids (such as salts) are removed from a solution (such as water). This is accomplished by household water pressure pushing the tap water through a semi permeable membrane. The membrane (which is about as thick as cellophane) allows only the water to pass through, not the impurities or contaminates. http://catalogs.indiamart.com/products/reverse-osmosis-systems.html
Main equipment in the power plant is Generator. It's cost is much higher than any other equipment so we will have to protect the generator from all the possible faults and errors.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
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Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Cosmetic shop management system project report.pdfKamal Acharya
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3. Synchronous Machines
Synchronous generators or alternators are used to convert mechanical
power to ac electric power derived from steam, gas, or hydraulic-turbine
Synchronous generators are the primary source of generation of electrical
energy we consume today generate at power stations
Big ac power networks (generating stations) rely almost exclusively on
synchronous generators
Synchronous motors of large ratings and size are preferred over induction
motors (Induction motors are cheaper for smaller ratings) and used for
constant speed industrial drives
4. Construction
Basic parts of a synchronous generator:
Rotor - dc excited winding
Stator - 3-phase winding in which the ac emf is generated
Cooling of different parts of synchronous generator depends
upon the operation of active parts.
6. 1. Most hydraulic turbines have to turn at low speeds
(between 50 and 300 r/min)
2. A large number of poles are required on the rotor
Hydro generator
Turbine
Hydro (water)
D 10 m
Non-uniform
air-gap
N
S S
N
d-axis
q-axis
Salient-Pole Synchronous Generator
8. L 10 m
D 1 mTurbine
Steam
Stator
Uniform air-gap
Stator winding
Rotor
Rotor winding
N
S
High speed
3600 r/min 2-pole
1800 r/min 4-pole
Direct-conductor cooling (using
hydrogen or water as coolant)
Rating up to 2000 MVA
Turbogenerator
d-axis
q-axis
Cylindrical-Rotor Synchronous Generator
10. Operation Principle
The rotor of the generator is driven by a prime-mover
A rotating magnetic field within the machine is produced
by a dc current in the rotor winding
It(The rotating magnetic field) induces a three-phase
voltage in the stator winding of the generator
11. Electrical Frequency
Electrical frequency produced is dependent on the
mechanical speed of rotation of a synchronous
generator and is locked or synchronized :
wheref = electrical frequency in Hz
P = number of poles
n= mechanical speed of the rotor, in r/min
12. Generated Voltage
The generated voltage of a synchronous generator is given by:
Where f = flux in the machine (function of If)
fe = electrical frequency
Kc= synchronous machine constant
If
E
Saturation characteristic of a synchronous generator
13. Voltage Regulation
Voltage Regulation (VR) is a convenient way to compare the
voltage behaviour of two different generators. At a given load,
power factor, and at rated speed to calculate the VR, the below
formula can be used
%
V
VE
VR
fl
flnl
100
Where Vfl = the full-load terminal voltage
Enl = no-load terminal voltage (internal voltage) at rated
speed .
when the load is removed without changing the field current.
For :
Lagging power factor (PF)=VR is fairly positive
unity PF=VR is small positive and
leading PF=VR is negative.
14. Equivalent Circuit_1
o The internal voltage Ef is not equal to the terminal voltage of
the generator.
o When there is no armature current flowing in the generator then
only Ef is same as the output voltage of a phase is machine.
o There are a number of factors that cause the difference between
Ef and Vt:
Armature reaction
The self-inductance of the armature coils.
The resistance of the armature coils.
The effect of salient-pole rotor shapes.
16. Phasor Diagram
Phasor diagram of a cylindrical-rotor synchronous generator,
for the case of lagging power factor
Lagging PF: |Vt|<|Ef| for overexcited condition
Leading PF: |Vt|>|Ef| for underexcited condition
17. Three-phase equivalent circuit of a cylindrical-rotor
synchronous machine
The voltages and currents of the three phases are 120o apart in angle,
but otherwise the three phases are identical.
+
Ia1
Ef1 jXs Ra+
VL-L
VL-L =3Vt
Vt
18. Determination of the parameters of the equivalent circuit
We need to calculate three main quantities in order to describe
completely from the equivalent circuit of a synchronous generator :
The saturation characteristic: relationship between If and f (and
therefore between If and Ef)
The synchronous reactance, Xs
The armature resistance, Ra
The above three quantities could be determined by performing the
following three tests:
Open-circuit test
Short-circuit test
DC test
19. Open-circuit test
The generator is turned at the rated speed
The terminals are disconnected from all loads, and the field current is
set to zero.
Then the field current is gradually increased in steps, and the
terminal voltage is measured at each step along the way.
It is thus possible to obtain an open-circuit characteristic of a
generator (Ef or Vt versus If) from this information
+
Vdc
If
Vt
20. Short-circuit test
Adjust the field current to zero and short-circuit the terminals of
the generator through a set of ammeters.
Record the armature current Isc as the field current is increased.
Such a plot is called short-circuit characteristic.
A
A+
Vdc
If
Isc
21. – then
– If the stator is Y-connected, the per phase stator resistance is
– If the stator is delta-connected, the per phase stator resistance is
DC Test
The purpose of the DC test is to determine Ra. A variable DC voltage
source is connected between two stator terminals.
The DC source is adjusted to provide approximately rated stator current,
and the resistance between the two stator leads is determined from the
voltmeter and ammeter readings
DCa RR
2
3
DC
DC
DC
V
R
I
2
DC
a
R
R
22. Determination of Xs
For a particular field current IfA, the internal voltage Ef (=VA) could
be found from the occ and the short-circuit current flow Isc,A could be
found from the scc.
Then the synchronous reactance Xs could be obtained using
IfA
Ef or Vt (V) Air-gap line
OCC Isc (A)
SCC
If (A)
Vrated
VA
Isc,B
Isc, A
IfB
scA
fA
unsat,saunsat,s
I
EV
XRZ
22
22
aunsat,sunsat,s RZX
scA
oc,t
scA
f
unsat,s
I
V
I
E
X
: Ra is known from the DC test.
Since Xs,unsat>>Ra,
23. Xs under saturated condition
Ia
Ef Vt=0
jXs Ra
+
+
EfVt=0
jIaXs
IaRa
Ia
scB
frated
sat,sasat,s
I
EV
XRZ
22
At V = Vrated,
22
asat,ssat,s RZX : Ra is known from the DC test.
Equivalent circuit and phasor diagram under condition
IfA
Ef or Vt (V) Air-gap line
OCC Isc (A)
SCC
If (A)
Vrated
VA
Isc,B
Isc, A
IfB
24. Short-circuit Ratio
Another parameter used to describe synchronous generators is the
short-circuit ratio (SCR). The SCR of a generator defined as the
ratio of the field current required for the rated voltage at open
circuit to the field current required for the rated armature current
at short circuit. SCR is just the reciprocal of the per unit value of
the saturated synchronous reactance calculated by
.u.pinX
I
I
SCR
sat_s
Iscrated_f
Vrated_f
1
Ef or Vt (V) Air-gap line
OCC
Isc (A)
SCC
If (A)
Vrated
Isc,rated
If_V rated If_Isc rated
25. Example 1
A 200 kVA, 480-V, 60-Hz, 4-pole, Y-Connected synchronous
generator with a rated field current of 5 A was tested and the
following data was taken.
a) from OC test – terminal voltage = 540 V at rated field
current
b) from SC test – line current = 300A at rated field current
c) from Dc test – DC voltage of 10 V applied to two terminals,
a current of 25 A was measured.
1. Calculate the speed of rotation in r/min
2. Calculate the generated emf and saturated equivalent circuit
parameters (armature resistance and synchronous reactance)
26. Solution to Example 1
1.
fe = electrical frequency = Pnm/120
fe = 60Hz
P = number of poles = 4
nm = mechanical speed of rotation in r/min.
So, speed of rotation nm = 120 fe / P
= (120 x 60)/4 = 1800 r/min
2. In open-circuit test, Ia = 0 and Ef =Vt
Ef = 540/1.732
= 311.8 V (as the machine is Y-connected)
In short-circuit test, terminals are shorted, Vt = 0
Ef = IaZs or Zs = Ef /Ia =311.8/300=1.04 ohm
From the DC test, Ra=VDC/(2IDC)
= 10/(2X25) = 0.2 ohm
Synchronous reactance 2
,
2
, satsasats XRZ
02.12.004.1 2222
,, asatssats RZX
Ia
Ef
Vt
j1.02 0.2
+
+
27. Parallel operation of synchronous generators
There are several major advantages to operate generators in
parallel:
Several generators can supply a bigger load than one machine
by itself.
Having many generators increases the reliability of the power
system.
It allows one or more generators to be removed for shutdown
or preventive maintenance.
28. Before connecting a generator in parallel with another
generator, it must be synchronized. A generator is said to be
synchronized when it meets all the following conditions:
The rms line voltages of the two generators must be
equal.
The two generators must have the same phase sequence.
The phase angles of the two a phases must be equal.
The oncoming generator frequency is equal to the
running system frequency.
Synchronization
Load
Generator 2
Generator 1
Switch
a
b
c
a/
b/
c/
29. Concept of the infinite bus
When a synchronous generator is connected to a power system,
the power system is often so large that nothing the operator of the
generator does will have much of an effect on the power system.
An example of this situation is the connection of a single
generator to the Canadian power grid. Our Canadian power grid
is so large that no reasonable action on the part of one generator
can cause an observable change in overall grid frequency. This
idea is idealized in the concept of an infinite bus. An infinite bus
is a power system so large that its voltage and frequency do not
vary regardless of how much real or reactive power is drawn
from or supplied to it.
30. Active and reactive power-angle characteristics
P>0: generator operation
P<0: motor operation
Positive Q: delivering inductive vars for a generator action or
receiving inductive vars for a motor action
Negative Q: delivering capacitive vars for a generator action or
receiving capacitive vars for a motor action
Pm
Pe, Qe
Vt
Fig. Synchronous generator connected to an infinite bus.
31. Active and reactive power-angle characteristics
The real and reactive power delivered by a synchronous
generator or consumed by a synchronous motor can be
expressed in terms of the terminal voltage Vt, generated voltage
Ef, synchronous impedance Zs, and the power angle or torque
angle d.
Referring to Fig. 8, it is convenient to adopt a convention that
makes positive real power P and positive reactive power Q
delivered by an overexcited generator.
The generator action corresponds to positive value of d, while
the motor action corresponds to negative value of d.
Pm
Pe, Qe
Vt
32. The complex power output of the generator in volt-
amperes per phase is given by
*
at
_
IVjQPS
where:
Vt = terminal voltage per phase
Ia
* = complex conjugate of the armature current per phase
Taking the terminal voltage as reference
0jVV tt
_
the excitation or the generated voltage,
dd sinjcosEE ff
_
Active and reactive power-angle characteristics
Pm
Pe, Qe
Vt
33. Active and reactive power-angle characteristics
Pm
Pe, Qe
Vt
and the armature current,
s
ftf
s
t
_
f
_
a
_
jX
sinjEVcosE
jX
VE
I
dd
where Xs is the synchronous reactance per phase.
s
tft
s
ft
s
tft
s
ft
s
ftf
t
*
a
_
t
_
X
VcosEV
Q
&
X
sinEV
P
X
VcosEV
j
X
sinEV
jX
sinjEVcosE
VIVjQPS
2
2
d
d
d
d
dd
34. Active and reactive power-angle characteristics
The above two equations for active and reactive powers hold good
for cylindrical-rotor synchronous machines for negligible
resistance
To obtain the total power for a three-phase generator, the above
equations should be multiplied by 3 when the voltages are line-to-
neutral
If the line-to-line magnitudes are used for the voltages, however,
these equations give the total three-phase power
Pm
Pe, Qe
Vt
s
tft
s
ft
X
VcosEV
Q&
X
sinEV
P
2
d
d
35. Steady-state power-angle or torque-angle characteristic of a
cylindrical-rotor synchronous machine (with negligible armature
resistance).
d
Real power or torque
generator
motor
pp/2
p/2
0
p
Pull-out torque
as a generator
Pull-out torque
as a motor
d
36. Steady-state stability limit
Total three-phase power: d sin
X
EV
P
s
ft3
The above equation shows that the power produced by a synchronous
generator depends on the angle d between the Vt and Ef. The maximum
power that the generator can supply occurs when d=90o.
s
ft
X
EV
P
3
The maximum power indicated by this equation is called steady-state stability
limit of the generator. If we try to exceed this limit (such as by admitting
more steam to the turbine), the rotor will accelerate and lose synchronism
with the infinite bus. In practice, this condition is never reached because the
circuit breakers trip as soon as synchronism is lost. We have to resynchronize
the generator before it can again pick up the load. Normally, real generators
never even come close to the limit. Full-load torque angle of 15o to 20o are
more typical of real machines.
37. Pull-out torque
The maximum torque or pull-out torque per phase that a two-pole
round-rotor synchronous motor can develop is
p
60
2 s
max
m
max
max
n
PP
T
where ns is the synchronous speed of the motor in rpm
P
d
P or Q
Q
Fig. Active and reactive power as a function of the internal angle
38. Synchronous Motors
A synchronous motor is the same physical machine as a
generator, except that the direction of real power flow is
reversed
Synchronous motors are used to convert electric power to
mechanical power
Most synchronous motors are rated between 150 kW (200 hp)
and 15 MW (20,000 hp) and turn at speed ranging from 150
to 1800 r/min. Consequently, these machines are used in
heavy industry
At the other end of the power spectrum, we find tiny single-
phase synchronous motors used in control devices and electric
clocks
P, Q
Vt
Motor
39. Operation Principle
The field current of a synchronous motor produces a steady-state
magnetic field BR
A three-phase set of voltages is applied to the stator windings of
the motor, which produces a three-phase current flow in the
windings. This three-phase set of currents in the armature
winding produces a uniform rotating magnetic field of Bs
Therefore, there are two magnetic fields present in the machine,
and the rotor field will tend to line up with the stator field, just as
two bar magnets will tend to line up if placed near each other.
Since the stator magnetic field is rotating, the rotor magnetic
field (and the rotor itself) will try to catch up
The larger the angle between the two magnetic fields (up to
certain maximum), the greater the torque on the rotor of the
machine
40. Vector Diagram
The equivalent circuit of a synchronous motor is exactly same as
the equivalent circuit of a synchronous generator, except that the
reference direction of Ia is reversed.
The basic difference between motor and generator operation in
synchronous machines can be seen either in the magnetic field
diagram or in the phasor diagram.
In a generator, Ef lies ahead of Vt, and BR lies ahead of Bnet . In a
motor, Ef lies behind Vt, and BR lies behind Bnet.
In a motor the induced torque is in the direction of motion, and in a
generator the induced torque is a counter torque opposing the
direction of motion
41. Vector Diagram
d
Ia
Vt
Ef
jIa Xs
d
Ia
Vt
Ef
jIa Xs
d
Bs
Bnet
BR
sync
Fig. The phasor diagram (leading PF: overexcited and |Vt|<|Ef|) and
the corresponding magnetic field diagram of a synchronous motor.
Fig. The phasor diagram of an underexcited synchronous
motor (lagging PF and |Vt|>|Ef|).
42. Application of Synchronous Motors
Synchronous motors are usually used in large sizes because in small sizes
they are costlier as compared with induction machines. The principal
advantages of using synchronous machine are as follows:
Power factor of synchronous machine can be controlled very easily by
controlling the field current.
It has very high operating efficiency and constant speed.
For operating speed less than about 500 rpm and for high-power
requirements (above 600KW) synchronous motor is cheaper than
induction motor.
In view of these advantages, synchronous motors are preferred for driving
the loads requiring high power at low speed; e.g; reciprocating pumps and
compressor, crushers, rolling mills, pulp grinders etc.