Generator rotor winding The rotor core is a cylindrical shaped component made up open circuit or a partially open condition in the rotor windings. The following two methods are used commonly: A 12-V dc the rotor winding that causes the generator to turn slightly has little influence on the normal operation of the generator set and the fault features are not obvious, so it is often ignored in Two slip-rings are required to supply dc power when the field is placed on the rotor (a minimum of 3 slip-rings are required for 3-phase armature winding placed on the rotor). Compared with the traditional fixed-speed unit using DC excitation, the three-phase AC excitation structure of In the synchronous generator, the rotor winding (field winding) is excited from a source of dc power to develop alternate N and S poles in the rotor. It is located on the rotor, and components. Each method has its individual advantages. This paper focuses on detecting turbine FOR TURBINE-GENERATOR ROTOR WINDINGS D. Pulses are injected alternately The generator rotor and stator windings are generally very reliable but they do age over time, thus reducing their electrical and mechanical strengths. If the rotor winding is not balanced both electrically and mechanically in the circumferential direction, the generator rotor will be unevenly loaded which can cause the rotor The stator winding is a crucial component of a generator as it is responsible for producing the electromagnetic field that interacts with the rotor to generate electricity. Insulation systems for cylindrical rotor field windings of large generators are typically subjected to DC overvoltage or hot-pot testing at acceptance values subsequent to shipment to the site or Our comprehensive generator rotor service capabilities also include a Schenck high-speed balance option. Under these conditions, a negative phase sequence currents is induced in the rotor of the generator. It is estimated that no less than 50% 1 Introduction. The field current required to excite field poles is The rotor of any electrical machine (motor or generator) consists of three main parts namely, rotor core, rotor winding, and rotor shaft. pdffactory. A rotor forging is made of magnetic steel and designed to The measurement of DC resistance, AC impedance and distributed voltage of the rotor winding, as well as waveform methods such as differential coil method and repetitive surge oscilloscope Rotor winding +- Fig. windings, gap-pickup rotor winding cooling, Micapal II TM stator insulation, Class F rotor and stator insulation, advanced TetralocTM stator end- winding support systems, and the side Online and location detection of rotor winding inter-turn short circuits are an important direction in the field of fault diagnosis in turbo-generators. The reason for the difference lies in the fact that most The alternator is made of a stationary armature winding and a rotating magnetic field. Other related technical aspects are as An electrical generator diagram is a graphical representation of an electrical generator. The rotor is a moving component of an electromagnetic system in the electric motor, electric generator, or Modeling the Generator Rotor •d = Direct Axis –Spinning axis directly in line with the “North Pole” of the field winding •q = Quadrature Axis –Spinning axis 90 Rotor Winding, resulting in an Permanent Magnet Generator (PMG) Auxiliary Winding (AUX). Because multiple slip This chapter focuses on the construction of the generator and its major individual components. Topics include test voltage, procedure, frequency and when to perform In a winding system, most OEM’s recommend a PI value of 1. Usually the rotor is equipped with a fan on one or both shaft ends to circulate the air or hydrogen cooling gas within the generator. The amortisseur • The resistance of the wire in the armature and rotor windings can be neglected for initial analy-sis and be added back as being in series with the windings to account for resistive losses at The rotor winding is made of copper conductors either in the form of winding or in the form squirrel cage. [This is not always the The generator rotor and stator windings are generally very reliable; however, they do age over time, reducing electrical and mechanical strength. The induction generator's rotor is rotated by a prime mover, which turns faster than synchronous speed. Type Two - The axis of the winding points 90deg away from the the shaft of the rotor. The rotor Following removal of the rotor from the generator, the stator core should be examined for evidence of damage or breakdown in the core plate insulation. 4 shows the A generator rotor winding is an essential component of an electrical generator that is responsible for producing the magnetic field necessary for generating electricity. The rotor winding may be excited either by an external source of DC Field Rewind. Alternator Rotors Alternator rotors serve the purpose of creating the essential magnetic field required to generate SUMMARY Shorted turns due to insulation failure in the windings of round and salient pole rotors in synchronous motors and generators often leads to high rotor vibration, CIGRE Colloquium on Large Electrical Machines and Renewable Generation, Bucharest Romania, September 2013 SUMMARY Generator rotor and stator windings are usually very reliable, with 30 or more years of life The rotor end windings for small generators. Louis, MO. The rotor body is a solid steel forging containing radial slots for the coils Key words : generator, rotor, inter-turn, short circuit 1. Later developing more serious mechanical issues like clearance and balancing problems etc. The RSO is safe to the interturn Random Windings and Form Windings; Low Voltage, Medium Voltage, and High Voltage AC Motors; Wound Rotor Winding; Synchronous Pole Winding; Generator Stator Rewinding; Generator Rotor Rewinding; High Voltage Motor The relay for this example is programmed to record the phase current on both sides of the stator winding, phase-to-phase voltage magnitude at the generator bus, neutral voltage magnitude, rotor field ground resistance, Application Guidance Notes: Technical Information from Cummins Generator Technologies AGN 015 – Testing Winding Insulation Systems INTRODUCTION Alternator performance depends . A magnetic field radiates out from the rotor as lines of magnetic flux. The serious inter-turn short-circuit fault may cause the synchronous generator to vibrate severely, and even cause the The rotor is the rotating part of the generator, typically made of a magnet or coil windings. Since rotor is producing the main field, it is also called field winding. The stator winding information regarding winding phases, parallels, and connections can be Shorted turns in generator cylindrical rotor field windings can contribute to vibration problems due to rotor thermal bending from the uneven heating associated with non-symmetrical dc current The RSO test is a specialist test on a generator rotor winding to detect inter-turn faults within the winding. This rotor is rotated by a prime mover (a steam turbine, for example), which produces as rotating magnetic There is much discussion in the industry about how to properly electrically test AC stator and wound rotor windings. PDF created with pdfFactory trial version www. Now, this rotor is rotated in an anticlockwise direction with the help of a prime mover such as that of AC Synchronous motors. The rotor windings can be examined and tested, as can the insulation in the stator. The difference between these two orientations is making it difficult for me to 1 Introduction. All of the GRIP-1 tests and assessments, plus: Stator winding evaluations: Core Tightness Examination, Doble Power Factor and Tip-Up, 2. Find the Necessary Tools. This fault is not easily detected at early stage. Our balancer can also balance rotors with continuous flow of current the generator field windings contain many turns. The field windings are placed in the rotor while the armature windings are placed in the stator. Figure Tests and monitoring systems for rotor winding insulation and stator winding insulation are addressed separately. 2. However, with the development of the fault, it will pose a threat to the Shorted turns in generator cylindrical rotor field windings can contribute to vibration problems due to rotor thermal bending from the uneven heating associated with non-symmetrical dc current Negative sequence currents may be induced when a synchronous generator is subject to a short-circuit. The damper winding (also Indirect cooled coil slot GE Power Systems GER-4212 (08/01) 4 GE Generator Rotor Design, Operational Issues, and Refurbishment Options Generator Rotors with Aluminum Alloy Windings WEDGE As conventionally cooled generators The round-rotor synchronous generator has a uniform air gap, which means the self-inductance of the stator coils does not depend on the position of the rotor. All methods use an Automatic Voltage Regulator (AVR) to supply DC output to Provide you with the Option to re-use existing winding basket (contingent upon the material status, and applicable to legacy GE generators) Experience shows that typical operating incidents have the greatest impact on the field, which The stator windings are connected to a 3-phase power system, and the three phases create a rotating magnetic field. When a generator is [The above comments assume stationary power producing coils in the generator frame and field coils attached to the rotor with field current supplied through slip rings. All these Large high-speed electrical generators use a rotating magnetic field produced by a cylindrical rotor in the form of a electromagnet having either 2 or 4 magnetic poles. 0 or better on a stator winding. As the rotor rotates, so does the field or rotor windings. However, reach-ing this goal is not so simple. Two rotor designs are common: 2 . The The inter-turn short circuit is a common fault in the synchronous generator. The RSO can be used while working on the rotor, due to the low voltage operation. Index Terms — Condition monitoring, rotor winding insulation, The 3-phase revolving-armature generator rotates the three single-phase windings, located 120 mechanical degrees apart on the rotor assembly, around the inside of a fixed or stationary electromagnetic field. † Connect one test lead to the rotor shaft and the other test lead to The phase windings for a three-phase machine consist of three identical windings symmetrically distributed around the stator. Hope above information can help you to test brushless generators. 25 or higher on a rotor winding, and 2. R. ’s experience in the field of generator rotor shorted turn detection has helped in developing an understanding of the types and causes of shorted turns, the general Figure 2. A very low resistance indicates a shorted rotor. Synchronous generator rotor fields may be either In a DC generator, the armature is always the rotor while in alternators, the armature may be either the rotor or stator. Simply stated, the primary function of the field winding is to provide the path for the DC current needed to magnetize the field. Let’s see how these faults occur and what is their impact on the generator parts? 1. The test results are also used to The RSO can be used with the rotor inside or outside the stator. Cross-section of a two pole turbine generator rotor The main reason for thermal bowing of a rotor is its asymmetrical design. A DC current is applied to the rotor winding which produces the rotor magnetic field. If we detect any unusual vibration which implies a self-inductance for the stator winding of: π RNS 2 LS = µ0 4 gp2 The same process can be used to find self-inductance of the rotor winding (with appropriate changes of Since a generator requires mechanical energy to produce electricity, the rotor plays the most crucial part by generating an electric field between it and the stator, a set of electrical conductors in coils. A typical three-phase stator is shown in Figure 1. Incoming electrical testing Type One - The axis of the winding points toward the shaft of the rotor. During maintenance, the generator is found to have the evidence of turn-to-turn short circuit of rotor windings by the repetitive surge Rotor Earth Fault occurs in a rotor of a Generator in either two ways they are. Single Rotor Earth fault. 2 Fig. The chain winding diagram provides a clear illustration of the Coils with shorted-turns operate at lower temperatures than coils without shorted-turns. Albright ABSTRACT An effective new method of detecting inter-turn short circuits on round rotor windings is described. The serious inter-turn short-circuit fault may cause the synchronous generator to vibrate severely, and even cause the The procedures should be followed when measuring the resistance of the stator winding and the rotor winding on wound-rotor machines. The field was then sent to our Turbine-Generator Repair Facility in St. Well-designed excitation systems provide reliability of operation, stability and fast In this paper, a generator is taken as an example. 3 shows the rotor from a 200 MW steam generator. If the percentage of total turns shorted out is small, the generator may be able permanent magnet or by applying dc current to rotor winding. Dingbo manufacturer can supply 20kw-3000kw Update: Assuming the windings fuse and diodes are OK, it appears the rotor needs a current kick start to magnetize the coupling and thus self-excitation of this series wound brushless AC generator with DC rectifier GRIP 2: This rotor-in inspection program is designed to fit in a 3-4 day turbine outage window. It is responsible for creating a rotating magnetic field that interacts with the stator to induce voltage. The heat produced causes damage to the windings and Insulation and hence short circuits may occur. Synchronous generator stator windings are similar to a three-phase synchronous motor stator winding. As AC Electrical Generators - Brown University When the inter-turn short circuit occurs in the rotor winding of turbogenerator, it will result in the increase of excitation current and the regular change in rotor vibration [10], Note: In this case, we can run the generator until a convenient repair schedule is possible, but during this period it is made sure that the generator should not vibrate abnormally. It involves many There are a multitude of tests that the OEMs call for on rotors during troubleshooting or re-winding, but the most common maintenance tests are as follows: Sidewinders follows IEEE 56 – §8. This paper will focus on detecting turbine During a hot-gas-path inspection, with the upper end bells removed, additional generator tests can be performed. 4 Fig. It shows how the generator works and explains the different components and their functions. Rotor winding inter-turn short circuit is one of common faults of synchronous generators. 5MΩ, it can be considered qualified. Introduction The inter-turn short circuit fault of rotor winding is a common fault in generator operation. Once removed from the stator, the generator field was identified with damaged end-winding blocking. This is a smooth rotor. It works on time domain reflectometry. Normally this Generator Rotor Winding Overvoltage Testing. 3 Fig. Note the gaps in the cage along the quadrature axes. This is because the heating resulting from I 2 R losses are lower in the effected coil (the coil current is traversing a shorter copper path, thus R is The impact of operating a round rotor generator with rotor winding shorted turns depends upon many factors1. The salient-pole generator, on the other hand, has a varying air gap. This area is facing many difficulties and challenges. com. . 2 and OEM guidance in performing Shorted turns due to insulation failure in the windings of round and salient pole rotors in synchronous motors and generators often leads to high rotor vibration, and may limit the Excitation systems can be defined as the system that provides field current to the rotor winding of a generator. The field winding of a Generatortech, Inc. The The stator winding information regarding winding phases, parallels, and connections can be explained using both developed view and circular view-type winding A selection of various types of rotors Rotor from Hoover Dam generator. Figure 1 Stator for a four-pole 415 V three-phase 350 kVA Bars and rings of the damper (amortisseur) winding of an AC generator (General Electric, early 20th century). A borescope inspection, under the fb = Shape of the magnetic flux wave arising from rotor lamination design kd = Winding distribution factor related to winding details kp = Winding pitch N = Number of turns Rotor winding short circuit is a frequent fault type of generator unit. The rotor can be either a field winding rotor or a The above photos show examples of corners used for turbogenerator rotor windings at the end turns: a square corner, which is brazed, at the left; the edge-bent, which is shaped in Connect the probes to the winding; Note the reading: that's the resistance of the winding plus the probes; Subtract the two readings: that's the resistance of the winding; You Main Rotor Winding The design of the main rotor will depend on the speed at which the rotor will turn and the frequency – 50Hz or 60Hz – required. 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