Induction Generator - 100255K
-
Upload
chamath-kirinde -
Category
Documents
-
view
85 -
download
2
description
Transcript of Induction Generator - 100255K
EE 2192 Laboratory Practice IV
INDUCTION GENERATOR
Name
Index No.
Field
Group
Date of Performance
Date of Submission
: W.M.C.N.S.Kirinde
: 100255K
: Electrical Engineering
: G6
: 2012/11/15
: 2012/11/29
Instructed by : K.L.J..Jayaranga
OBSERVATION SHEET
PRACTICAL
NAME
INDEX NO.
FIELD
GROUP
DATE OF PERFORMANCE
DATE OF SUBMISSION
INSTRUCTED BY
: Induction Generator
: W.M.C.N.S.Kirinde
: 100255K
: Electrical Engineering
: G6
: 2012/11/15
: 2012/11/29
: K.L.J. Jayaranga
(1) Self – Excited Induction Generator
Part (a): No - load characteristics for varying capacitance and constant prime mover speed
Speed: 2500 rpm
Residual Voltage: 2.912 V
Capacitance (µF) Voltage (V) Current (A) Frequency (Hz)
50 0 0 41
55 0 0 42
60 0 0 42
62 240 2.2 41
65 250 2.4 41
70 274 2.8 41
Part (b): No load characteristics for varying prime mover speed and constant capacitance
Capacitance: 62 µF
Voltage (V) Speed (rpm) Current (A) Frequency (Hz)
200 2380 1.75 39.50
220 2432 1.95 40.35
240 2500 2.20 41.30
260 2560 2.50 42.60
270 2600 2.60 43.20
Part (c): Performance of load generator with constant speed
Speed: 2500 rpm
Capacitance: 70 µF
Voltage (V) Gen. Current (A) Load Current (A) Frequency (Hz) Torque (Nm)
270 2.80 0.0 41.40 1.7
265 2.75 0.4 41.00 2.1
262 2.70 0.8 41.10 2.6
258 2.70 1.2 41.22 2.8
245 2.60 1.5 40.90 3.2
Part (d): Performance of the loaded generator without speed regulation
No – load Speed: 2500 rpm
Speed (rpm) Voltage (V) Gen. Current (A) Load Current (A) Frequency (Hz) Torque (Nm)
2500 270 2.80 0.00 41.40 1.6
2426 266 2.50 0.38 40.05 2.0
2373 224 2.25 0.70 39.10 2.2
2339 205 2.10 0.96 38.40 2.3
2320 190 1.90 1.18 37.90 2.4
(2) Grid Connected Induction Generation
Current (A) Voltage (V) Power (W) Speed (rpm) Frequency (Hz) Torque (Nm)
1.6 230 0 3014 50.10 1.4
1.6 230 40 3025 50.20 1.6
1.7 230 240 3050 50.20 2.3
1.9 230 420 3073 50.10 2.9
2.1 230 480 3086 50.25 3.1
CALCULATIONS
| | | |
(1) Self – Excited Induction Generator
Part (a): No - load characteristics for varying capacitance and constant prime mover speed
From the graph Line Voltage vs. Magnetizing Current,
Magnetizing Current at the voltage 240V, Im = 2.2A
Frequency at the voltage 240V, f = 41.30 Hz
From the graph Line Voltage vs. Magnetizing Current,
Magnetizing Current at the voltage 240V, Im = 2.2A
⁄
⁄
√
√
(2) Grid Connected Induction Generator
Efficiency
Specimen Calculation
Wattmeter Reading = 24W
Multiplication Factor = 20
Hence,
output power =
Torque = 3.1 Nm
Angular Speed = 3086 rpm
Power Factor
Specimen Calculation
GRAPHS
1) (a) No-Load characteristics for varying capacitance and constant prime mover speed
Line Voltage vs. Magnetizing Current
Line Voltage vs. Capacitance
(b) No-Load characteristics for varying prime mover speed and constant capacitance
Voltage vs. Speed
Frequency vs. Speed
Magnetizing Current vs. Speed
(c) Performance of the loaded generator with constant speed
Voltage vs. Load Current
Frequency vs. Load Current
Generator Current vs. Load Current
(d) Performance of the load generator without speed regulation
Voltage vs. Load Current
Frequency vs. Current
Torque vs. Speed of the prime mover
2) Grid Connected Induction Generator
Power Output vs. Speed
Line Current vs. Speed
Efficiency vs. Speed
Power Factor vs. Speed
DISCUSSION
Comment why the no-load test was designed to result in a lower frequency than the
rated frequency of 50 Hz.
In this no-load test we need to obtain parameters for a wide range of line voltage like
from 200V to 280V for better results. In order to do that, we need to keep the operating point
of the induction generator to be in the non-linear region. If the operating point lies on the
linear region, then the range of the voltage won’t be considerably large enough to do the
practical over a wide range. When the frequency increases and reaches a value like 50Hz,
the gradient increases and operating point lies on the linear region then. Thus, the no-load
test is designed to result in a lower frequency than the rated frequency of 50Hz.
Discuss the importance of induction generators both self-excited and grid connected in
power generation of Sri Lanka.
Induction generators have the ability to produce useful power at varying rotor speeds.
Hence, they are really important for the usage in wind turbines and mini and micro hydro
installations. In Sri Lanka, we can find a lot of small waterfalls, especially in the central
parts. Induction generators can play a vital role in the mini and micro hydro power stations
because of their simplicity in electrical and mechanical aspects. Induction generators are not
appropriate for high power applications. Because of the coastal areas all around Sri Lanka,
wind power stations can be installed. These induction generators are more rugged than other
types and require no brushes or commutators. Thus, inductions generators are really
important for windmills too. They usually require no regulation process and the power factor
correction also can be easily provided by capacitor banks. Induction generators are
comparatively cheap and compact in size making them ideal for small scale generation in Sri
Lanka.
Self-Excited Induction Generators are really useful in isolated power generation in Sri
Lanka. They do not need an external power supply to produce the magnetic field. It makes
them the ideal choice for the wind power generation in remote areas. The magnetic field
does not deteriorate with the time which causes a drop in generated voltage in these
generators unlike the other generators with permanent magnets. The synchronous alternator s
in standalone power generation is being replaced gradually by these generators due to their
advantages over the alternators.
In grid connected systems, the frequency and the voltage at the machine are governed
by the electric grid. Grid connected systems are usually between 10 kW and 100 kW. The
power should be normally conditioned using an inverter before fed to the grid. Self-
commutated inverters need a reference from the utility grid to hold synchronization. This
can be easily done with induction generators.
Discuss about each graph plotted.
1. Self-excited Induction Generator
Part (a):- No Load characteristics for varying capacitance and constant prime mover speed
Line Voltage vs. Magnetizing Current
When the magnetizing current increases, the line voltage also increases. But after some time,
the line voltage tends to saturate with the further increment of magnetizing current. The
relation between the two parameters as follows where E, Im, ω, Lm indicates Line voltage,
magnetizing current, angular frequency and inductance of the equivalent magnetic circuit of
the machine respectively.
| | | |
Line Voltage vs. Magnetizing Current
With the increment of capacitance, the line voltage increases drastically. Further, line
voltage tends to saturate in lower capacitance conditions when the prime mover speed is at a
constant.
Part (b):- No Load characteristics for varying prime mover speed and constant capacitance
Voltage vs. Speed
With the speed of the prime mover, voltage increases linearly.
Frequency vs. Speed
With the speed of the prime mover, frequency increases linearly.
Magnetizing Current vs. Speed
With the speed of the prime mover, magnetizing current increases linearly.
Part (c):- Performance of the loaded generator with constant speed
Voltage vs. Load Current
Voltage decreases when the load current increases. At lower load currents the decrement of
the voltage is very low. However with the load current, voltage decreases drastically.
Frequency vs. Load Current
According to the results obtained, it is significant that frequency remains constant while load
current is being increased. Hence, it is found that at constant speeds, the frequency of the
loaded generator does not depend on load current.
Generator Current vs. Load Current
Generator current is being decreased with the load current.
Part (d):- Performance of the load generator without speed regulation
Voltage vs. Load Current
The voltage decreases with the load current in this case too. But in numbers, the decrement
of voltage is dramatically large when there’s no speed regulation.
Frequency vs. Load Current
Frequency decreases with the load current in the absence of speed regulation unlike in the
earlier case, the speed regulated scenario. It is tend to remain constant for very low load
currents for a moment; but drastically decreases then.
Torque vs. Speed of the prime mover
Torque, speed relationship here is somewhat linear and torque decreases uniformly with the
speed of the prime mover.
2. Grid Connected Induction Generator
Power Output vs. Speed
The increment of power output with respect to the speed of the grid connected induction
generator is somewhat linear.
Line Current vs. Speed
Line current increases with the speed in a linear manner.
Efficieny vs. Speed
Efficiency increases with the speed. However it is tend to reach a maximum at more speeds
because the gradient is decreasing. Then after reaching its maximum, the efficiency will
decrease again at very high speeds.
Power factor vs. Speed
Power factor shows a non-linear relationship with the increment of speed. At lower speeds
close to 3000rpm the increment is very low and when it reaches a values like 3030, 3040
rpm it tends to show a linear relationship. Then again at higher speeds close to like 3100rpm
the power factor tends to reach a maximum point and then decreases with further increment.
REFERENCES
http://en.wikipedia.org/wiki/Induction_generator
http://autonopedia.org/renewable_energy/Generators/motors_as_generators.html
http://www.ijcee.org/papers/278-E747.pdf