Tap changers are devices fitted to power transformers that regulate output voltage levels by altering the transformer turn ratios (paragraph 1). On-load tap-changers (OLTCs) are commonly used in power grids and industries to continuously regulate voltage during operation (paragraph 2). OLTCs offer variable control to maintain supply voltage within specified limits by selecting different transformer taps, which correspond to different turn ratios and voltage outputs (paragraphs 3-5). Modern OLTCs are designed to change taps while energized since off-load tap changers interrupt power supply (paragraph 6).
Automatic generation control (AGC) is a system for adjusting the power output of multiple generators at different power plants, in response to changes in the load. Since a power grid requires that generation and load closely balance moment by moment, frequent adjustments to the output of generators are necessary. The balance can be judged by measuring the system frequency; if it is increasing, more power is being generated than used, which causes all the machines in the system to accelerate. If the system frequency is decreasing, more load is on the system than the instantaneous generation can provide, which causes all generators to slow down.
The inverter is a static device. It can convert one form of electrical power into other forms of electrical power. But it cannot generate electrical power. Hence the inverter is a converter, not a generator.
Nowadays, it is very important to maintain voltage level. Controlling of that voltage is also important. This Presentation contains methods of voltage control.
A synchronous motor is electrically identical with an alternator or AC generator.
A given alternator ( or synchronous machine) can be used as a motor, when driven electrically.
Some characteristic features of a synchronous motor are as follows:
1. It runs either at synchronous speed or not at all i.e. while running it maintains a constant speed. The only way to change its speed is to vary the supply frequency (because NS=120f/P).
2. It is not inherently self-starting. It has to be run up to synchronous (or near synchronous) speed by some means, before it can be synchronized to the supply.
3. It is capable of being operated under a wide range of power factors, both lagging and leading. Hence, it can be used for power correction purposes, in addition to supplying torque to drive loads.
On Load Tap Changer (OLTC) is used in "High Power Transformers" to control output voltage, when electric load on transformers get increase the output voltage get decrease due to internal voltage drop inside winding, change in tap is required to maintain output voltage. OLTC is a device which perform tap changing in High Power Transformers during On Load conditions and is powered by a motor.
Chokeless welding transformer with load series motoreSAT Journals
Abstract
Welding is a materials-joining process that produces coalescence of materials by heating them to the welding temperature with or
without the application of pressure or by the application of pressure alone, and with or without filler metal. It is used to make
welds. It is observed that the welding transformer with choke or movable core is having large size, so to reduce the size we are
replacing the choke with one coil. This coil functions same as the choke. This coil helps to reduce the size as well as the cost of the
welding transformer. The forced air cooled transformer consists of an exhaust fan which rotates at a constant speed whether the
welding work is going or not. So, the more energy will be wasted there. To avoid this, the load series motor is used. The load
series motor as the name suggests is a motor, which is to be connected in series with a load. The load series motor, which shaded
pole motor but designed in such a way that if connected in series with load, it will run and speed of such motor will be
proportional to the load current. The ordinary exhaust fan motor can be, easily replaced by the load series motor.
Keywords: Rotary Switch, and Load Series Motor.
Automatic generation control (AGC) is a system for adjusting the power output of multiple generators at different power plants, in response to changes in the load. Since a power grid requires that generation and load closely balance moment by moment, frequent adjustments to the output of generators are necessary. The balance can be judged by measuring the system frequency; if it is increasing, more power is being generated than used, which causes all the machines in the system to accelerate. If the system frequency is decreasing, more load is on the system than the instantaneous generation can provide, which causes all generators to slow down.
The inverter is a static device. It can convert one form of electrical power into other forms of electrical power. But it cannot generate electrical power. Hence the inverter is a converter, not a generator.
Nowadays, it is very important to maintain voltage level. Controlling of that voltage is also important. This Presentation contains methods of voltage control.
A synchronous motor is electrically identical with an alternator or AC generator.
A given alternator ( or synchronous machine) can be used as a motor, when driven electrically.
Some characteristic features of a synchronous motor are as follows:
1. It runs either at synchronous speed or not at all i.e. while running it maintains a constant speed. The only way to change its speed is to vary the supply frequency (because NS=120f/P).
2. It is not inherently self-starting. It has to be run up to synchronous (or near synchronous) speed by some means, before it can be synchronized to the supply.
3. It is capable of being operated under a wide range of power factors, both lagging and leading. Hence, it can be used for power correction purposes, in addition to supplying torque to drive loads.
On Load Tap Changer (OLTC) is used in "High Power Transformers" to control output voltage, when electric load on transformers get increase the output voltage get decrease due to internal voltage drop inside winding, change in tap is required to maintain output voltage. OLTC is a device which perform tap changing in High Power Transformers during On Load conditions and is powered by a motor.
Chokeless welding transformer with load series motoreSAT Journals
Abstract
Welding is a materials-joining process that produces coalescence of materials by heating them to the welding temperature with or
without the application of pressure or by the application of pressure alone, and with or without filler metal. It is used to make
welds. It is observed that the welding transformer with choke or movable core is having large size, so to reduce the size we are
replacing the choke with one coil. This coil functions same as the choke. This coil helps to reduce the size as well as the cost of the
welding transformer. The forced air cooled transformer consists of an exhaust fan which rotates at a constant speed whether the
welding work is going or not. So, the more energy will be wasted there. To avoid this, the load series motor is used. The load
series motor as the name suggests is a motor, which is to be connected in series with a load. The load series motor, which shaded
pole motor but designed in such a way that if connected in series with load, it will run and speed of such motor will be
proportional to the load current. The ordinary exhaust fan motor can be, easily replaced by the load series motor.
Keywords: Rotary Switch, and Load Series Motor.
The present-day electrical power system is A.C. i.e. electric power is generated, transmitted and distributed in the form of alternating current. The electric power is produced at the power stations which are located at favourable places, generally quite away from the consumers. It is delivered to the consumers through a large network of transmission and distribution
Automatic voltage regulator(avr)/voltage boosterJestem Zhou
Farady Automatic voltage regulator technical specfication. we can install a voltage regulator in the place that the voltage drop is too large than normal range, to ensure the electric equipment working ordinarily.
1. A tap changer is a device fitted to power
transformers for regulation of the output
voltage to required levels.
On-load tap-changers (OLTCs) are
indispensable in regulating power
transformers used in electrical energy
networks and industrial applications
2. Tap changer alters the turn
ratios of the transformer on the
system by altering the number
of turns in one winding of the
appropriate transformer.
Tap changers offer variable
control to keep the supply
voltage within these limits.
Tap changers are of two types
◦ Off load
◦ On load
However since the offload tap
changer causes interruption in
the supply on load tap
changers are more preferred
in in today power system.
3. By the transformation
ratio
V1/V2= N1/N2
V2=N2/N1×V1
From the above equation
by altering the turn ratio
to suitable values the
secondary voltage can be
adjusted desired level.
Lets – N1=2750,
N2=100, turn ratio=
N1/N2=2750/100=27.5
why we choose this turn
ratio - V1=11 KV,
V2= 400Volt
Transformation ratio
V1/V2=
11000/400=27.5
4. Each tap corresponds to different
transformation ratio. For Initial
installation we need to choose a
suitable tap as per our voltage levels.
Tap changers provides 5 to 20 %
voltage range for voltage regulation.
5.
6. An on load tap changer
has 3 major steps
a. Tap selector- it selects
the appropriate tap
b. Fixed contact- These
contacts hold a fixed
position
c. Moving contact- This
contact moves to open/
close the appropriate
taps.
7. Based on the AVR
feedback the suitable
tap is selected fig (a) to
(c)
After the tap is selected
the moving contact
moves and it closes both
taps for a while. It
moves further and finally
completely opens to
earlier tap and closes to
the next tap fig (d) to (i)
8. The moving contact closes two taps
for a while during the tap changing,
due to which a circulating current
starts to flow. This current needs to
be minimized. For limiting this
current resistor or reactors are used.
The moving contact is operated by
charged spring tension and it
completes the process within 30 to
70ms. The spring is charged by
motor drives.
While opening and closing the
contacts sparks are produced due to
arising recovery voltage. The
contacts are kept in oil or SF6 gas ,
which work as insulation medium as
well as arc quenching.
10. Motor drive unit (MDU)- This unit has got a
motor diver and other necessary controls.
Motor charges the spring to rapidly perform
the switching. Power is transferred via shaft &
gear mechanism.
Diverter switch /Oil compartment- This has
the diverter switch, which has moving and
fixed contacts. It is filled with oil or SF6 gas
to avoid the sparking & quenching during
opening and closing of the contacts.
Tap selector- It has different tap
combinations as specified by the customer
requirements and different standards.
11.
12. Due to opening closing of contacts the sparks
produce and the oil degrades over the time. The oil
test & analysis needs to be done in lab at regular
interval
The contacts wear over the time after number of
operations.
The oil seals damage over the time and leakage
happens. Maintaining the oil level is must. For
condition monitoring its must to check for oil leak
and level regularly.
Oil dripping is dangerous for environment as well.
OLTC includes a lot of gear, spring and mechanical
parts which have a usual wear and tear, that need to
be taken care as an when required.
13. Vacuum type OLTC use the vacuum interrupters
which has some advantages over oil / SF6.
It is hermetically sealed and has no interaction
with surrounding medium despite the arc.
Contacts wear is lower than OIL/SF6.
No aging or quenching medium is required.
Its more environment friendly.
Vacuum interrupters perform up to 600000
operation with out replacement.
Has low maintenance cost and greater reliability.
15. A dual voltage transformer can be defined as
the one which is capable of providing two
types of voltage.
A dual voltage transformer has two windings
in primary and two other windings in
secondary.
By connecting the both windings either of
primary or secondary in series or parallel two
different voltages are produced.
16. From the figure two
primary windings and
two secondary
windings are
connected in series
resulting in 240 volt
input and 24 volt out
put voltage.
17. From the adjacent
figure the primary and
secondary windings are
connected in parallel,
resulting 120 volt
input and 12 volt out
put voltage.
There can be either
type of arrangements
as per requirement.
18. The details in the
adjacent figure shows
the winding arrangement
of a dual transformer. It
produces 33/7.1 and
33/11 kV voltages
according to
arrangement of winding.
The unit produces
different outputs, based
on the connections as
advised in the name plate
details.
Upon simplifying the
connection diagrams
they turn out to be series
connected winding for
33/11 kv output and
combination of series
and parallel for 33/7.1
kv output.