What are the different types of generator rotors?
Types of Generator Rotors There are two basic types of generator rotors:conventional windings (indirect-cooled) anddirect windings (conductor-cooled). Both typesand their variations are discussed.
What is a motor rotor?
What is rotor? The rotor is the rotating part of the motor and can be found inside the stator. As with the stator, also the rotor core consists of electrically laminated steel sheets. Inside the rotor slots, there are aluminum windings that are cast together with short-circuit rings.
What is the rotating part of a generator called?
Some OEMs such as GE refer to the rotating portion of the generator as the field. Others, such as Siemens refer to it as the rotor. Both are correct, but both have their limitations.
What is the difference between a stator and a rotor?
Unlike the stator, where virtually all of the windings are buried under many layers of mica and epoxy insulation, the rotor windings are open to the environment, and have minimal insulation. For this reason, rotors are particularly vulnerable to ground faults and inter-turn shorts (“shorted turns”).
What is the function of a rotor?
Rotors are the moving part in an Alternator that have permanent magnets that move around the Stator's iron plates to generate an Alternating Current (AC). Rotors require existing motion to function, so only once the engine or turbine is already running will a Rotor work with a Stator to provide a charge.
What is difference between of rotor and stator on generator?
The rotor is the rotating part of a machine. In electrical motors or generators, the whole linear synchronously rotating part of the machine is termed the rotor. The stator is the non-moving, fixed counterpart in a machine.
How do you test a generator rotor?
The AC impedance test is used to find indications of shorted rotor turns. The test is performed by means of applying an AC voltage across the field winding and raising it in 10-volt steps up to 100-120 volts, or till the current supply gets maxed out.
What happens when an AC generator rotor turns?
Whenever the TG rotor shaft rotates, an electromotive force (emf) develops across the generator or armature terminals of the pilot exciter due to the effect of the rotation of the magnetic field of the permanent magnet. The AC voltage thus produced is converted to DC voltage from DC by the rectifiers.
What is the purpose of rotor in DC generator?
The rotor is a moving component of an electromagnetic system in the electric motor, electric generator, or alternator. Its rotation is due to the interaction between the windings and magnetic fields which produces a torque around the rotor's axis.
Is the rotor inside a stator?
The rotor is placed inside the core of the stator. The three-phase is supplied to the stator winding which produces the rotating magnetic field. The rotor rotates inside the rotating magnetic field. Thus, an emf is induced because of the interaction of magnetic field of rotor and stator.
How do you fix a generator that runs but no power?
0:002:54generator runs but no electricity quick fix - YouTubeYouTubeStart of suggested clipEnd of suggested clipOff. So you can check the brushes. And such too if you want see if they're bad or making contact onMoreOff. So you can check the brushes. And such too if you want see if they're bad or making contact on ground. But try this first if you can or even if you've already checked the brushes.
How do you test a generator alternator?
0:389:05How to Test an Alternator - YouTubeYouTubeStart of suggested clipEnd of suggested clipSo 20 in this case. Here's the negative terminal. And the positive terminal on the battery. You wantMoreSo 20 in this case. Here's the negative terminal. And the positive terminal on the battery. You want to make sure these terminals are clean so that you'll get a reading when you do this test.
How do you flash a generator with a battery?
Connect F+ to the positive pole of the battery. Hold the F- lead by the insulated portion of the lead wire, touch F- to the negative pole of the battery for about 5 to 10 seconds, then remove. Reconnect F+ and F- to the regulator. Repeat the procedure if the generator fails to build voltage.
How does a rotor power a generator?
The rotor generates a moving magnetic field around the stator, which induces a voltage difference between the windings of the stator. This produces the alternating current (AC) output of the generator.
Why does a generator need an exciter?
The main purpose of exciter in a generator(alternator) is to provide stationary rotating magnetic field. Which is used to induce the e.m.f in the armature coil. So, DC power is given to exciter and the exciter is nothing but a coil, and the exciter creates a magnetic field.
What are the three basic parts of an electric generator?
No matter the type of motor, there are three basic parts: a stator, a commutator, and a rotor.
Does generator have stator and rotor?
Generator Design and Construction There are two main components in the generator, the rotor and the stator. The generator must also have a source of DC current to magnetize the rotor, called the exciter.
What is a stator on a generator?
The stator is the stationary part of a rotary system, found in electric generators, electric motors, sirens, mud motors or biological rotors. Energy flows through a stator to or from the rotating component of the system.
How do rotors and stators work?
0:091:42Difference Between stator and Rotor - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd field winding are the two parts of the rotor. The three phase supply is given to the winding ofMoreAnd field winding are the two parts of the rotor. The three phase supply is given to the winding of the stator whereas the rotor is excited by the DC supply.
How do I test my rotors and stators?
To perform a high current rotor test, you remove the rotor from the stator and apply a high current through the shaft of the rotor. Then an infrared camera will allow you to visually inspect the surface of the rotor for localized hot spots. Those localized hot spots reveal problems with the rotor bar.
What is the difference between a stator and a rotor?
The main differences between the stator and rotor include the following. Stator. Rotor. It is n inactive part of the stator. It is the rotary part of the stator. It includes a stator core, outer frame, and winding. It includes winding and core.
What is an asynchronous motor?
Similarly, asynchronous motors like induction and synchronous motors like alternators and generators include an electromagnetic system that includes a stator as well as a rotor. In an induction motor, there are two types of designs available like squirrel-cage & wound. In alternators and generators, there are two types of designs available like ...
What is the moving part of an electromagnetic system?
Definition: It is the moving part in an electromagnetic system of the motor, generator and an alternator. It is also called as the Flywheel, rotating magnetic core, an alternator. In an alternator, it includes permanent magnets that move approximately to the iron plates of the stator to produce an AC ( Alternating Current ). It uses existing motion for its function. The rotation of this can be occurred because of the interaction between magnetic fields & the windings which generate torque in the region of the axis.
How does an induction motor work?
In a three-phase induction motor, once an AC is applied to the rotor then the windings of stator strengthen to generate a rotary magnetic flux. The flux generates a magnetic field in the air gap among the stator & the rotor to induce a voltage for generating the current throughout the bars. The circuit of this can be shorted & the flow of current will be in the conductors.
What is a squirrel cage induction motor?
It is the rotary part in the squirrel cage induction motor. It is a kind of AC motor. It includes steel laminations with a cylinder shape. The conductors like copper otherwise aluminum are fixed on its surface
What is electromagnetic rotation?
The electromagnetic rotation is the first rotary machine and it was designed by “Ányos Jedlik” from 1826 to 1827 with the help of a commutator as well as electromagnets. In the motor or generator, both the parts like rotor and stator play a key role. The main disparity between these two is that the stator is an inactive part of the motor whereas the rotor is the rotary part. Similarly, asynchronous motors like induction and synchronous motors like alternators and generators include an electromagnetic system that includes a stator as well as a rotor. In an induction motor, there are two types of designs available like squirrel-cage & wound. In alternators and generators, there are two types of designs available like salient pole otherwise cylindrical. This article discusses an overview of the rotor in the motor/generator.
What is the act of the rotary flux and the current?
The act of the rotary flux & the current generates a force to generate a torque to begin the motor. The rotor in an alternator can be designed with a wire coil enclosed in the region of an iron core.
What is a rotor in a machine?
What is a Rotor? It is the rotating part of the machine. It is attached to a shaft that is connected with the key at the end as a lock. This rotating part is considered as the rotor that rotates inside a magnetic field when torque is developed.
When was the rotor invented?
The rotor was invented in the early 1800s and it was discovered by the naval officers R. P. C. Spengler and Theo A. van Hengel. Earlier it was used in Rotor dynamics for the encryption of files especially used in cryptography. The invention of this type is also supported by Gustaf de Laval who is working for the development of turbine machinery.
What are the different types of rotating parts?
There are different types of rotating parts. They are squirrel cage and slip ring type. The squirrel cage type and stator are considered as the squirrel cage induction motor whereas the slip ring type and stator together are considered as the slip ring induction motor. The slip ring motor is shown in the figure below.
How many poles does a stator have?
There is no specific number of poles for the construction it depends on the number of stator poles. If the stator has 4 poles, then the rotating part should also have 4 poles. This type of rotating part response will change automatically with the change made in the stator.
What is the supply given to a stator?
Supply given to stator is three-phase. It is self-excited by the induction principle. Frictional losses are more. It requires more insulation because of carrying the heavy current. Frictional losses are less. It requires less insulation. We had studied what is the rotor and its other parts in this discussion.
What is low starting torque?
Low starting torque as resistance is less. Starting current is more since the resistance is less. These drawbacks can be overcome by making the changes in the cross-sectional area of the rotating conductor bars. This achieved by skewing the rotating bars of the conductors.
How to increase starting torque?
To improve the starting torque, we connect external resistance in series with the machine that acts as an additional resistance helpful in increasing the starting torque. Usually, in a slip ring, the winding is wound in star in order to increase the starting torque.
What is the difference between a rotor and an armature?
The correct term from an electrical engineering standpoint is “field”, whereas the term “armature” always refers to the alternating current component whether it is stationary or rota ting. The rotor transmits its torque to the stator by means of locking or synchronizing its magnetic field rotation to that of the stator.
What is RSO in rotor?
RSO stands for Recurrent Surge Oscillography. RSO is a low-voltage test which applies a high-frequency (RF) train of pulses into one end of the rotor and detects the energy wave form coming out the other end. It is similar to the RADAR concept in that it uses a time-of-flight concept to detect electrical obstructions such as shorted turns within the winding. The test alternately injects energy in one direction and measures the energy from the other side, then switches directions. This provides two oscilloscope traces. In an ideal rotor winding with no shorted turns, the two waveforms can be superimposed perfectly over each other. If they cannot be perfectly matched up, this is an indication of shorted turns. We use the “math” function on the oscilloscope to subtract channel 1 from channel 2 to give a “difference” trace. If traces on channels 1 & 2 are identical, then CH1 – CH2 will be equal to zero.
What happens when a generator breaker is open?
If the generator breaker is open, and excitation is on, the generator will produce full rated voltage, and zero current. With the breaker open, or if the unit is on a small island grid where it is the main or only generator (isochronous mode), raising excitation will result in an immediate raise in grid voltage.
Is a rotor a field or a rotor?
Others, such as Siemens refer to it as the rotor. Both are correct, but both have their limitations. “Rotor” is convenient because it tells us that it is a rotating component. “Field” tells us that it is a DC electromagnet with multiples of two poles.
Do rotors have insulation?
Unlike the stator, where virtually all of the windings are buried under many layers of mica and epoxy insulation, the rotor windings are open to the environment, and have minimal insulation. For this reason, rotors are particularly vulnerable to ground faults and inter-turn shorts (“shorted turns”). As with all generator testing, the objectives are ...
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Shortened turns are usually detected by increased bearing vibration levels in operation. This is due to the pressure on the turn to turn insulation generated by the centrifugal force.
What is the impact of a double earth fault on the rotor?
What is the impact of Double earth fault on the rotor? If more than one earth fault occurs, a short circuit between the faulty points on the winding occurs. This may cause an unbalance magnetic field and mechanical damage may occur in the bearing of the machine.
Can a rotor be prevented from a fault?
We can’t prevent the occurrence of rotor earth faults as the rotor is continuously revolving it is prone to earth faults always but certainly, we can provide a Rotor Earth Fault Protection-64R to a generator to prevent the damage occurring to a rotor as a result of various earth faults.
Is the magnetic field produced by the rotor sinusoidally distributed?
In addition, the magnetic field then produced by the rotor might no longer be sinusoidally distributed around the periphery and it might also be asymmetric, the flux densities at corresponding points on the poles being different.
What are the problems with generator rotors?
The mostcommon problems occurring with generatorrotors are shorted turns and breakdown ingroundwall insulation. These two concerns willbe discussed in detail.
Is hydrogen cooled generator well sealed?
A hydrogen-cooled generator is well sealed and should seevery little contamination. A TEWAC (totallyenclosed water to air cooled) unit will requiresmall amounts of make-up air that can intro-duce particulates into the generator. An OV(open ventilated) generator is most likely to seelarge amounts of contamination introducedinto the field.
Can you repair an existing rotor?
It is often possible to repair/refurbish an exist-ing rotor to satisfactory working condition.However, in certain circumstances, it maybecome necessary to replace the existing rotor.The following situations are instances whenreplacement is preferable to repair:
Why does a generator rotor bow out?
Asymmetrical thermal growth of the generator rotor coils can also be caused by excessive contamination restricting cooling or ventilation pathways. As with turn-to-turn shorts, blocked ventilation can cause uneven axial expansion as some coils operate at higher temperatures than others. The rotor will bow out on the side of the most significant ventilation restriction.
What causes a bow in a generator rotor?
The main windings of a rotor must be allowed unrestricted axial thermal expansion and contraction. Improperly positioned blocking can cramp or restrict this axial growth, thus causing a bow in the rotor body. A generator rotor that demonstrates thermal sensitivity caused by creepage or distance blocking issues will bow out on the same side as the restriction.
What are the components of a generator?
A generator is comprised of several different components, e.g. rotor body forging, copper coils, steel retaining rings, insulating slot cells, turn insulation, and creepage blocks. Each is comprised of unique materials having distinctive coefficients of thermal expansion. The differences in coefficients of the two major components, the rotor body forging and the copper coils, are significant (over 30%) and the associated forces surprisingly enormous. If these forces become restricted or otherwise unequally distributed, the rotor can develop a bend or bow. The development of temperature within a rotor is predominately a by-product of the current or amperage applied to the copper coils. This current or amperage is the source of thermal expansion and any associated thermal sensitivity.
How many wedges are in a generator rotor?
Some generator rotor designs have only three, two, or even one wedge per slot. Such configurations are much more susceptible to wedge related irreversible thermal sensitivity. Additional safeguards must be employed when these rotor body wedges are removed to facilitate rewind or repairs. It is critical that each and every wedge be trial-fit into its exact position, and fine-tuned as required to assure proper fit.
What causes rotor imbalance in generator?
Generator rotor imbalance can come from a number of different sources, i.e. coupling misalignment, component non-concentricity, rubbing, oil issues, bearing, and journal issues. Each has unique characteristics. Thermal sensitivity has its own recognizable characteristics.
Does a TGR react to field current?
As stated above, a thermally sensitive TGR’s vibration will react to changes in field current. Bear in mind that a Turbine Generator’s vibration may also react to changes in megawatt loading. It is therefore important to ascertain whether excessive vibration is megawatt loading induced or field current induced.
What is a rotor core?
As with the stator, also the rotor core consists of electrically laminated steel sheets. Inside the rotor slots, there are aluminum windings that are cast together with short-circuit rings. This is done by making holes in the lamination so that when they are stacked, channels will be formed through the rotor core.
Why is there an air gap between the stator and the rotor?
There is an air gap between the stator and the rotor and since it is known that air conducts magnetic fields poorly the gap can’t be too big. The airgap cannot either be too small since metallic objects expand when heated and as the rotor gets warm there will not be enough space for it to rotate inside the stator.
What is stator?
The stator is the assembly of the fixed parts performing the function of supporting – at least partially – the motor, but fundamentally it constitutes the part of the magnetic circuit that includes the inductor windings housed in special slots made in correspondence with its internal surface.
Why do rotors have skewered cores?
The windings inside the rotor do not go straight but are skewered to reduce electrical noise and vibration. The rotor core helps to conduct the magnetic field from the stator to the rotor windings.
What are the main parts of a stator?
The three main parts of the stator include the stator core, stator winding, and the outer frame. The two main parts of the rotor include rotor core and field winding. The three-phase supply is given to the winding of the stator. DC supply. The winding arrangement of the stator is more complex.
Why is a rotor winding highly insulated?
Stator winding is highly insulated because high voltage induces in it. The rotor winding has low insulation. The friction loss of the stator is high. The friction loss of the rotor is low. The cooling system of the stator is simple. The cooling system of the rotor is complex.
Can a three phase winding be delta connected?
The three-phase stator windings can be star- or delta-connected; this can be achieved with motors equipped with a terminal box with 6 terminals so that it is possible to feed the same motor with different three-phase network voltages.
Construction
Working/Function
Types
Squirrel-Cage/Rigid Rotor
Slip Ring/Wound
Difference Between A Stator and A Rotor
- Usually, in a generator, it rotates when a conductor is rotated inside the magnetic flux it induces an emf that further produces a torque. This torque, in turn, rotates the rotating part.