Automatic Voltage Regulator


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This article is closely related to the article on the excitation system because the working principle of the AVR is to regulate the flow of reinforcement on the exciter.
Units operating system AVR (Automatic Voltage Regulator) function to keep the generator voltage remains constant in other words, the generator will remain stable release tension that always is not affected at the expense of change was always changing, because the load affects the voltage output of the generator.

AVR is the working principle of strengthening the current set on the exciter. If the generator output voltage below the nominal voltage of the generator voltage, the AVR will improve the flow of reinforcement on the exciter. And vice versa if the generator output voltage exceeds the nominal voltage generator AVR will reduce the flow of reinforcement on the exciter. Thus, if the generator output voltage changes can be stabilized by the AVR will automatically due equipped with equipment such as tools used for the minimum or maximum limitation of the amplifier that works automatically.






AVR is operated with a power supply of the permanent magnet generator (PMG) is an example AVR voltage 110V, 20A, 400Hz. And got the sensor from potential transformer (PT) and current transformers (CT).





The sections on AVR unit

a. Sensing circuit
Three-phase generator voltage sensing circuit is given in the PT and 90R past the first, three-phase current and voltage output is derived from the 90R and then rectified by diode circuit, and flattened by a series of capacitors and resistors and voltage can be adjusted by VR (variable resistance). The advantage of the sensing circuit is to have a fast response to the generator output voltage.

Output voltage response is proportional to the generator output voltage is directly proportional as shown in the picture.





b. Comparative amplifier
Comparative amplifier circuit is used as a comparison between the sensing circuit with the set voltage. Sensing voltage with a large set of voltage does not have the same value, thus the difference / voltage range is large. Voltage difference is called the error voltage. This will be eliminated by setting a VR (variable resistance) on the set of voltage and voltage sensing.

c. Amplifier circuit
Current flow from the D11, D12, and R34 is the main amplifier circuit or the strengthening of the lowest levels. Comparative output from the amplifier and the output from over-excitation limiter (OEL) is a negative voltage and the negative voltage then the input OP201. When over-excitation limiter (OEL) or the minimum excitation limiter (MEL) is not operating, the output of the amplifier was confirmed by comparative OP201 and OP301 OP301 summed with the input of the output from dumping circuit. Amplifier OP401 is to balance the relationship between the voltage meter entrance and the output voltage of OP201 and OP401 are shown in the chart below.





d. Automatic and manual change over the mixer circuit
The circuit is arranged in Auto-manual shifting relationships and a circuit for controlling voltage generators penguatanmedan. Auto-manual change over and mixer circuit voltage settings on manual operation performed by the strengthening of the generator field 70E, and at the automatic and manual change over manually operate the mixer circuit AVR (automatic voltage Rregulator) can not operate. And if this series on the AVR auto condition should be working to arrange a large generator field current.

e. Limited circuit
Limited circuit is to determine more restrictions and less reinforcement (excitation) for setting the output voltage on the system excitacy, VR125 to bookmark more than the output terminal C6 and VR126 for a minimum of limiting the output terminal C6.

f. Syncronizing phase circuit
Thyristors are used to control the unit output voltage thyristors by using control signals provided at the gates of thyristors by altering the angle signal at the gate of thyristors. Phase synchronization circuit is used to change the angle of the gate thyristors in accordance with the voltage output from the boundary of synchronization and control signals are also provided on the thyristors below the image synchronization.

g. Thyristor firing circuit
This series of complementary thyristors to provide control signals to the gates of thyristors.

h. Dumping circuit
Dumping the sensor circuit will provide the reinforcement of the AC voltage applied to the exciter and amplifier to be used as feed back circuit with an input terminal OP301.

i. Thyristors Unit
An array of thyristors and diodes. And also use a fuse (fuse) is used as a safety melting and is also equipped with indicators to monitor the working of thyristors are mounted on the front of thyristors for each phase are given two parallel arranged fuse and when mistakes or broken one is still able to operate.

j. MEL (minimum excitacy limiter)
MEL (minimum excitation limiter) is to prevent excessive output on the generator and the addition of reinforcement (excitacy) to increase the generator terminal voltage at a constant level. This circuit is used to detect the operation of the generator that is by detecting the output voltage and current in the generator. Inijuga circuit used for comparing the output voltage of the generator with minimum excitation that has been setup. This circuit will give a signal in the circuit limit the AVR when the excitation exceeds the minimum, and then from the MEL output (Minimum Excitation Limiter) upheld by the amplifier.





k. Automatic follower
The working principle of this tool is to complement the strengthening of the settings manually by 70E. To adjust the operation of generators in the benchmarking of the terminal voltage fluctuations by the error signal. This enabled them to maintain the stability of the voltage on the generator. This operation is used for manual setting (70E) to accuracy levels which have been adjusted excitacy. Operating conditions and comparing the fluctuations of the generator terminal voltage by an error voltage signal. It is used as the handle to maintain stability of the voltage on the generator with the change of load.
Automatic Follower is used to detect the signal output from the voltage regulator error and automatic operation with manual adjuster makes a zero value. The circuit is to increase the signal and reduce signal controlled by 70E. By rotating 70E for controlling the signal on this circuit.



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Transformer Tap Changer


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Tap-changer is a device changes the voltage ratio of transformation to get a better secondary operations (desired) of the network voltage / primary fickle.

To meet the voltage quality of service according to customer needs (electricity distribution), the voltage output (secondary) transformer must be changed as desired. To meet this, then on one or on both sides of the transformer winding is made tap (bugs) to change the transformation ratio (ratio) transformer.





There are two methods tap changer:
  1. Changing the taps in the transformer no-load conditions. Tap changer which can only operate to move the transformer tap transformer in a state does not load, called "Off Load Tap Changer" and can only be operated manually.
  2. Changing the load transformer tap-in condition. Tap changer which can operate to move the tap-transformer, the transformer load condition, called "On Load Tap Changer (OLTC)," and can be operated manually or automatically




Transformers installed in substations typically use tap changer can be operated in a state loaded and installed in a transformer primary side. While peppery voltage transformer in a transformer plant, or in a small capacity, typically using a tap changer is operated only during power transformers without load.

OLTC consists of:
1. Selector Switch
2. deverter switch
3. transition resistor

To isolate the transformer from the body (ground) and reduce the heat transfer process at the tap, the OLTC immersed in insulating oil which is usually separate from the main transformer insulating oil (there are several transformers that compartment become one with the main tank).

Because the process of switching tap relations phenomenon occurred in the oil-electric, mechanical, chemical and heat, the OLTC insulation oil quality will quickly decline. depending on the number of works and the presence of abnormalities in OLTC.


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Standardization of Electric Motors


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Electric motors are commonly used in industrial world is asynchronous electric motor, with the two global standards IEC and NEMA. Asynchronous motor based IEC metric (millimeters), while the NEMA electric motors based Imperial (inch), in applications there is the unit of power in horsepower (hp) or kilowatt (kW).

Electric motors in IEC standards are divided into several classes according to its efficiency. As a standard in the European Union, the division of this class become EFF1, EFF2 and EFF3. For EFF1 class is the most efficient electric motors, at least waste of energy, while EFF3 already may not be used within the EU, because wasting fuel in power stations and will automatically generate the largest carbon sink, thus further polluting the environment.

Applicable IEC standard is IEC 34-1, this is a standard governing the rotating electric-powered equipment. There are plenty of electric motor manufacturers, but only in part truly follow the directives and IEC 34-1 efficiency levels also follow directives from the European Union.

Many producers of electric motors that do not follow IEC standards and European Union so that their products become cheaper and more were sold, many developing countries manjdi market for these products, which in the long-term users of financial squandering, because of the higher electricity bills each year.

Institutions that regulate and ensure the efficiency level is CEMEP, a European consortium set up by the factories are well-known electric motor, with a view to saving the environment by reducing carbon pollution globally, because a lot of wasted power in the use of electrical load.
For example, in an average industrial electricity consumption for electric motors is approximately 65-70% of total electricity costs, so using an efficient electric motor that will reduce overhead costs of production, thus raising product competitiveness, especially with the increase in electricity tariff every year , hence the use of electric motors EFF1 it was time to become mandatory.
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Universal Motor


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Universal motors including single phase motors using stator winding and the winding rotor. Universal motors used on the sewing machine, hand drill motor. Routine maintenance is done by replacing the carbon brush or it spring. Its Construction is simple, reliable, easy to operate, small power, big torque universal motor is used for domestic appliances.



Universal shape of the motor stator comprises two stator poles. Winding rotor having twelve winding grooves and comes commutator and carbon brushes which connect in series between the stator winding with a winding rotor. High-speed universal motor has about 3000 rpm. Figure below shows the rotor and stator.



Example of using a universal motor is on the sewing machine.


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Shaded Pole Motor


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Shaded Pole Motor include motor single phase small power, and is widely used for household appliances as the motor of the fan, blender. Construction is very simple, at both ends of the stator there are two wires attached and connected shorted function as shaded phase.

Winding wound around the stator core to form such transformer winding. Rotor shaped squirrel cage and stator axis is placed at the house sustained two bearing.



Shaded pole motor-sectional slices show two parts, namely the stator winding and stator with two wires shaded pole. Parts of the rotor cage is placed in the middle of the stator, see picture




Swivel torque generated by the cleavage phase shaded pole by a wire. Simple construction, small power, reliable, easy to operate, maintenance-free and adequate supply with AC voltage of 220 V, type shaded pole motors are widely used for small household appliances.

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Capacitor Motor


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Single phase capacitor motors are widely used in household appliances such as water pump , washing machine, freezer, air conditioning . Simple construction with small resources and working with electricity supply voltage 220 V, therefore making the capacitor motor is widely used in household appliances.




Stator winding consists of the main winding terminals U1-U2 notation, with the notation and auxiliary winding terminals Z1-Z2-mesh nets connected to the terminals L1 and U1, and the neutral wire connected to the terminal N U2. Capacitors work function to the main winding phase angle difference with the auxiliary winding approaching 90 °.
Setting the direction of motor rotation can be done with a capacitor (see figure):
• To produce rotation to the left (counterclockwise) working capacitor CB connected to the terminals U1 Z1 and Z2 and the terminal is coupled with the terminal.
• Round to the right (clockwise) a capacitor connected to the terminal work Z1 and Z2 terminals U1 and U1 is coupled with the terminal.





Capacitor motors with power above 1 kW is equipped with two capacitors and one centrifugal switch. U1-U2 primary winding is connected with the netting L1 and Neutral N. Z1-Z2 auxiliary winding connected in series with the capacitor CB job, and a starting capacitor CA serial with contacts normally close (NC) of the centrifugal switch, see figure .

Initially the main winding, and auxiliary winding voltage gain from the netting L1 and Neutral. Then two capacitors CB and CA, both of which form a closed loop so that the rotor began to spin, and when the rotation approaches 70% nominal speed, the centrifugal switch contacts will open and close normally decided auxiliary capacitor CA.




The function of the two capacitors are connected parallel, CA + CB, was to increase the initial torque value to lift the load. After reaching 70% of motor rotation, the centrifugal switch is disconnected so that only the working capacitor CB are still working. If the two capacitors is damaged then the motor torque will decrease drastically, see figure





Examples of the use of motor capacitor is on the electric water pump and compressor.


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AC Motors


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Based on the characteristics of an electric current flowing, the AC motor consist of two types, namely:

1. AC electric motor / ac 1 phase
2. AC electric motor / ac 3 phase



The working principle of AC Single Phase Motor

Single phase AC motor different is how it works with three-phase AC motor, where the three-phase AC motors for winding stator there are three turns of the play and the resulting field in the rotor cage induction and interactions occur which generate rotation torque. Whereas on single phase motor has two stator winding, which is the main phase winding (winding U1-U2) and the auxiliary phase winding (winding Z1-Z2), see figure.
















The main turns of copper wire using a larger cross section, so have the impedance is smaller. While the auxiliary winding is made of copper coil with small diameter, so the impedance is bigger than the main winding impedance.

Auxiliary winding currents I auxiliary graphs and the main winding currents I main different phases of φ, this was due to differences in the two turns of the impedance magnitude. This phase shift between the current difference causes the total current, is the vector sum of the main flow and auxiliary flow. The main magnetic field produced by the main winding phase is also different for φ with the help of magnetic field.
















Z1-Z2 auxiliary winding energized first I auxiliary produce perpendicular magnetic flux Φ, moments later the main winding U1-U2 I main energized primary. which has positive value. The result is a magnetic field shifted by 45 ° with counterclockwise direction. This went on until one cycle sinusoid, resulting in a rotating magnetic field on entanglement stator.
Rotor single phase motors with three phase motor rotor is shaped wire rods which are connected shorted edges and resembles the form of a squirrel cage, hence often called squirrel cage.






Cut by the rotor winding turn the stator field, resulting induced voltage, the interaction between the field and turn the stator magnetic rotor will rotate in the rotor produces torque.
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