https://www.generatortech.com/shorted-turn-theory daily 0.75 2026-03-31 https://www.generatortech.com/shorted-turn-theory/blog-post-one-66xrw monthly 0.5 2026-01-02 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/13f99de9-e820-484b-b1cc-803aabfe9777/Rotor+x-section+-+6+coils%2C+with+probe.jpg Shorted Turn Theory - Overview of Shorted Turn Theory & Flux Probe Testing - Make it stand out Rotor Cross-section - shows a two-pole rotor with 6 coils/pole and a single short in Coil 5-Pole A (Coil 5A, 20 total turns). The change in the heat produced by each coil due to that short is also displayed. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/1f78151f-7782-4a86-9172-529b5c8b1009/Annotated+waveform+-+6+coils.jpg Shorted Turn Theory - Overview of Shorted Turn Theory & Flux Probe Testing - Make it stand out Analysis Graph - from a rotor with 6 coils/pole and a Coil 5A turn short. Labels on the graphs identify features of interest. Compare with the rotor cross-section to understand how the waveform ‘s peaks correlate with the coil slots. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/9e9043f6-81f4-4bee-ad0d-5f465593819a/AG+with+Power+Angle+Anim+-+copyright.gif Shorted Turn Theory - Overview of Shorted Turn Theory & Flux Probe Testing Analysis Graph Animation - FDZC position (green line) moves to right toward the smaller coils (Coils 1 and 2) as real load increases. Reducing field current (negative MVARS) also moves the FDZC to the right. The FDZC position is determined by the Rotor Power Angle. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/9deb6b30-d9c8-4ce1-a315-da5e23cabfa5/LSO+Coil+5A+TS+anim-+copyright.gif Shorted Turn Theory - Overview of Shorted Turn Theory & Flux Probe Testing - Make it stand out Lead Slot Overlay Graph Animation - a pole-to-pole comparison of peaks shows the Coil 5A short is only detectable at low loads (when FDZC position is close to alignment with the #5 coils). Testing at just full load would have missed this turn short. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/6b0fbfc9-8d6b-4c25-a393-ee64725b55e1/Trend+curve.jpg Shorted Turn Theory - Overview of Shorted Turn Theory & Flux Probe Testing - Make it stand out Shorted Turn Indication Trend Curve - the indication for a true short will be optimized when the waveform’s FDZC position is closely aligned with that coil. https://www.generatortech.com/shorted-turn-theory/shorted-turns-cause-effect-bn9ch-x9at5-k8yst monthly 0.5 2026-03-31 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/44df9b13-4c3c-4c7e-82ed-488c3882b23a/Alsthom+Rotor+with+current+flow+diagram.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 1 - Rotor with 6 Coils/Pole and both retaining rings and the rotor wedges removed. The #1 coils have 17 turns and Coils 2-6 have 22 turns, producing 254 total turns in the winding. The average length of a turn is about 7.2 m (24 ft). The entire length of the rotor winding is about 1.8 km (1.1 miles). A schematic of the current flow through the turns in Pole A shows where coil-to-coil and pole-to-pole connectors are needed (the connectors are not visible in photograph). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/63c8a944-72eb-4db5-9840-1a8d0b160b45/Rotor+x-section%2C+with+end-turns+pic.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 2 - Rotor cross-section with 7 Coils/Pole and a rotor showing end-turns of winding after the retaining ring was removed. Note the blocking used between the coil stacks to maintain coil separation. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/d8b62aac-196a-42d2-88e8-270c62866dee/Two-pole+rotor+with+descriptions.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 3 - Large two-pole rotor with a collector rings. Current flows from one collector ring down the shaft (Figure 6) to where it connects to the bottom turn of Coil 1A. The current traverses all the turns used in each coil in Pole A and then passes through a pole-to-pole connector to get to Pole B, where it travels through each turn in that pole before heading back up the shaft to the other collector ring. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/f6ec035b-8399-4269-89d6-e49af13e8b06/Shaft+copper+picture.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 4 - A rotor shaft opened to see the copper conductors (axial leads) that carry current between the collector rings and starting turn of the #1 coils. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/06e51369-4ae3-4526-94cb-8866c5bcadda/Main+lead+j-strap+to+Coil+1.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 5 - Main lead connection from shaft copper to bottom turn of Coil 1. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/e8f1d9c5-f0cc-4306-9441-30aad9b48121/Two-pole+7-coil+diagram.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 6 - Diagram showing how coil-to-coil and pole-to-pole connectors link the coils into one series loop. In this case, the coil-to-coil connectors between Coils 1-2, Coils 3-4 and Coil 5-6 are between the top turns of those coils and are visible when the retaining ring is removed (Figure 7). Not shown in this diagram: for each turn in each coil, the turn travels down the rotor body to the turbine-end area in one coil slot and makes a u-turn to return to the collector-ring area in the other coil slot (see Figure 1 above). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/d07a5a1c-63b1-4912-afae-040c4de5054c/Coil-to-coil+connectors.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 7 - Coil-to-coil connections in a 7 Coil/Pole rotor winding where the connection from the shaft copper axial leads was to the bottom turns of the #1 coils. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/2c14eb11-9c25-4e2f-954f-4df954729e83/Coil+Diagrram+-+5+turns%2C+short+animation.gif Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 8 - Coil winding schematic with five total turns - The short between Turn 3 and Turn 4 allows current to bypass a complete turn (gray) in the coil, leaving 4 active turns and reducing the magnetic field produced by the coil. It doesn’t matter where the short is located along the two turns since the short will always bypass a complete turn and have the same effect in reducing the magnetic field. Therefore, while a flux probe test can determine the number of shorts in a coil, it cannot tell where the shorts developed along the affected turns. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/5524d80d-f216-4161-8017-d30b1bd8a644/Extended+Coil+3A+TS.gif Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 9 - Alternate diagram illustrating a turn-to-turn short in Coil 3A. The short contact (red T-T) carries the full excitation current, bypassing a complete turn in that coil. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/99f607cd-9fb4-4a4c-af9b-07434ce9bd9d/Turn+short+damage+-+insulation+holes+and+melted+copper.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 10 - Examples of damage at turn short locations. Three turn short locations are shown in three strips of interturn insulation. Melted copper damage at the contact point between two turns is shown for one of the turns. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/11d6a97e-6d3a-4280-a1f4-190a1c6330ff/Coil+2B-Coil+3B+short+LSO.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 11 - Lead Slot Overlay Graph that shows the Coil 2B-Coil 3B short. Higher loads would have shown the coil-to-coil short much better than this, but rotor vibration was limiting load to less than 50% full load. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/aaba78b1-a3e0-4391-8a62-6e2f4ed37356/Rotor+x-section+-+8+Coils%2C+Coil-to-coil+26+TS.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 12 - Rotor cross-section showing location of the 26 total turns bypassed due to Coil 2B-to-Coil 3B short. The combination of a thermal rotor bow and rotor magnetic asymmetry produced severe vibration that limited the unit to less that 50% of rated load. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/2aa95653-ffe7-4882-bfe9-54ee1726c7a5/Coil-to-coil+short+-+Coil+2B+to+Coil+3B.jpg Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 13 - After the retaining ring was removed, the flux probe test prediction was confirmed. Top turn distortion in Coils 2B and 3B made contact between those two turns, allowing current to bypass all of the turns used in those two coils (Figures 13 and 14). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/98301c6b-6285-4673-9425-4d7179a6dab3/Coil-to-coil+short+-+Coil+2B+to+Coil+3B.gif Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 14 - Diagram showing how contact between top turns of Coil 2B and Coil 3B allowed current to bypass all 26 turns used in those two coils. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/6c4956c2-d3d8-40dd-a207-1c4652539ecf/Extended+coil+B%2C+C-C.gif Shorted Turn Theory - Rotor Winding Description and Types of Turn Shorts - Make it stand out Figure 15 - Alternate diagram illustrating how a coil-to-coil short between top turns of Coil 2B and Coil 3B allows current to bypass all the turns in those two coils. https://www.generatortech.com/shorted-turn-theory/the-data-acquisition-amp-analysis-program monthly 0.5 2025-12-20 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/166bdc51-790c-4b2a-838a-92e839cb6fcf/Raw.jpg Shorted Turn Theory - The Data Acquisition & Analysis Program Raw Flux Probe Graph - shows the raw data recorded from the flux probe. This is a 110 MVA generator with a two-pole rotor, 6 coils/pole using 18 turns in Coil 1 and 20 turns in Coils 2-6. The winding has a single turn short in Coil 5A. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/4af6f15d-e3fc-4757-9a98-0206bd082ddd/AG.jpg Shorted Turn Theory - The Data Acquisition & Analysis Program - Make it stand out Analysis Graph - shows the raw data (red) with the flux density curve (dotted blue) overlaid. Each numbered peak correlates to a coil slot in the rotor body. The flux density zero-crossing (FDZC) position is marked with a green vertical line in all graphs other than the Raw Data Graph. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/97103dd8-f890-4f4a-b3af-4f5b16c9826d/ASO.jpg Shorted Turn Theory - The Data Acquisition & Analysis Program - Make it stand out All Slots Overlay Graph - shows an overlay graph with both the leading and lagging coil slots. For a synchronous generator, the FDZC position will always be in the leading slot region, which means the lagging coil slots are far from the FDZC. As a result, turn short indications in the lagging slot region are normally not well resolved and false indications are much more common. For example, the Coil 5A turn short indication is clearly detectable in the leading slots peaks (close to the FDZC), but not in the lagging slot peaks of Coil 5. For this reason, we normally display turn shorts using the Lead Slots Overlay Graph. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/9944b0f4-a6f6-4990-894a-474bc1642d93/LSO.jpg Shorted Turn Theory - The Data Acquisition & Analysis Program - Make it stand out Lead Slots Overlay Graph - shows an overlay of each pole’s leading slots. The short in Coil 5-Pole A (1 short with 20 total turns) is clearly displayed at this lower load whose FDZC position is well aligned with Coil 5. At higher loads, when the FDZC position is close to the smaller coils (Coils 1-3), the Coil 5A short is not detectable (see Lead Slots Overlay Graph animation in Overview of Shorted Turn Theory). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/b2ca727d-696e-4f58-889b-569ef5c10eab/Summary.jpg Shorted Turn Theory - The Data Acquisition & Analysis Program - Make it stand out Summery Sheet Printout - shows four graphs, plus the Shorted Turn Data Table. The percentage decrease is printed for the smaller pole of each coil. A turn short indication is printed if its calculated magnitude exceeds the default threshold of 0.50 turn shorts. At higher loads, when the FDZC position is close to the smaller coils (Coils 1-3), the Coil 5A indications drops below the 0.50 threshold. https://www.generatortech.com/shorted-turn-theory/blog-post-four-dx328 monthly 0.5 2026-03-04 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/581cdc82-cebf-4543-a6ac-821254132859/MWS+VS+FDZC+-+Two-Pole+example.gif Shorted Turn Theory - Need for Recording a Wide Range of Loads - Make it stand out Figure 1 - MWS Load vs FDZC Position Graph - shows how the FDZC position depends upon both real and reactive power. Startup test data recorded at 0 MVARS until full load was reached. At full MWS load (112.5 MWS), reactive load was varied in both the negative and positive direction. An optimum test would record a set of waveforms whose FDZC positions closely aligned with each rotor coil (red filled data points). Negative MVARs are often needed at full real load to align the FDZC position with the smallest rotor coils (Coils 1 and 2). Generatortech software automatically records these optimized waveforms as load is changing. The inset shows a waveform that produced a FDZC of 4.0 (55.1 MWS, 0.0 MVARS). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/089471bf-2240-4a7c-a2ee-70f8fc8d6aa3/M9+x-section.jpg Shorted Turn Theory - Need for Recording a Wide Range of Loads - Make it stand out Case 1: Rotor Cross-Section of a 2-pole rotor with 8 Coils/Pole showing the location of a true short in Coil 8A. Competitor’s testing at full load falsely claimed the rotor was free of turn shorts. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/c62aa3e0-43f2-4dcd-8162-25579f15e4e1/M9+animate%2C+Coil+8A+TS%2C+copyright.gif Shorted Turn Theory - Need for Recording a Wide Range of Loads - Make it stand out Case 1: Lead Slots Overlay Graph Animation - the single short in Coil 8A was not detectable at loads higher than about 25% of full load. However, the short was obvious in low load waveforms. True turn short indications are maximized in waveforms whose FDZC positions are close to alignment with the affected coil. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/4a321352-ee79-479a-90d0-0d644d41c7e2/M5+x-section.jpg Shorted Turn Theory - Need for Recording a Wide Range of Loads - Make it stand out Case 2: Rotor cross-section showing no true shorts. The false turn short indications seen in Coils 4 and 5 at both low and high loads are modulation artifacts and will not impact normal operation. Competitor’s testing at full load falsely claimed the rotor winding had two shorts. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/7a66e90a-9b61-46c0-81db-1489629a4c10/M5+animate%2C+False+TS%2C+copyright.gif Shorted Turn Theory - Need for Recording a Wide Range of Loads - Make it stand out Case 2: Lead Slots Overlay Graph Animation - the false short indications in Coil 4 and Coil 5 were seen in both low and high loads. In medium loads, where the FDZC positions were closer to alignment with those coils, the false indications disappeared. False indications are minimized in waveforms whose FDZC positions are close to alignment with the affected coil. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/7ead587f-f417-4a2b-a57c-05386002972d/Flux+Modulation+Effects+on+Peak+Heights+Animation.gif Shorted Turn Theory - Need for Recording a Wide Range of Loads - Make it stand out Modulation Effects on Peak Heights - This test was performed with a temporary flux probe intentionally adjusted to be too close to the rotor surface in order to emphasize modulation effects on coil slot peak heights. For a given coil, the peak size will be at a minimum when the FDZC (vertical green line) is aligned with that coil slot since that condition minimizes the modulation effects for that coil. The peak size of coils far from the FDZC are almost entirely due to modulation effects, reducing detection sensitivity for true shorts. https://www.generatortech.com/shorted-turn-theory/shorted-turns-cause-effect-bn9ch-x9at5 monthly 0.5 2026-02-26 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/06cf6c55-e3bb-4da4-9b6e-ba57154cd16b/Insulation+strips+with+burn+holes.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Three separate strips of inter-turn insulation showing holes that resulted in turn shorts. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/5cf996b0-ec34-42b9-abbb-cd942fa8d9ce/Melted+copper+at+TS.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out The high current density from the initial point contact between turns produced a spot weld that provided a low resistance short. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/055fd37e-bcba-4ae0-a7f2-f0821719b164/insulation+and+copper+turn+damage+-+small.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Example showing both the hole in the insulation and the copper damage at a shorted turn contact. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/9e5e1a47-20f8-4908-8b1e-803e2e81625b/Serious+turn+distortion+under+RR.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Distortion of the top turns under the retaining ring is fairly common. This pictures shows gross distortion of multiple turns, which resulted in multiple turn shorts. A coil-to-coil short appeared to be imminent. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/6382aa61-a3e3-46ce-ae77-738305b5145a/Shear+force+insulation+damage+animation.gif Shorted Turn Theory - Causes of Shorted Turns - Make it stand out When turn-to-turn movement occurs, tremendous shear forces act on the thin insulation layer, This can create tears or displace insulation to produce contact that allows current to bypass a turn. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/ac64c8e3-b641-42ac-9986-61b68d635877/Insulation+migration+chart.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Insulation migration led to a rapid increase in turn shorts in the two gas turbine rotors. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/597b997a-917b-496d-b6e6-ffb52fa80740/Bump+insulation+damage+animation.gif Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Whatever it is, the way you tell your story online can make all the difference. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/d673e9b0-3857-4b8a-af59-ab28c55a93f8/Overspeed+event+-+Coil+6B+TS+animation.gif Shorted Turn Theory - Causes of Shorted Turns - Make it stand out A large 800 MVA generator had tested free of shorts. Six months later, an overspeed event raised rotor speed to 3960 RPM, which results in a new Coil 6B short. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/a32b3923-1631-4ff9-818a-7624226e31ee/Misplaced+block+-+Coil-to-coil+short%2C+LSO+graph.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out A large jump in vibration was investigated with a flux probe test, which clearly showed a coil-to-coil short between Coils 3A and 4A. The contact was unusual in that it was between the bottom turns of the two coils and it bypassed 20 total turns in the winding. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/8a69a90f-2896-4b96-89c0-229922f6566b/Misplaced+block+-+Coil-to-coil+short.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out The misplaced block in this image was originally located at the top of the stacks, but it slid down to the corners of end-turns. This allows the turns in Coil 3A to tilt over, allowing contact between the bottom turns of Coil 3A and 4A, bypassing all turns in those two coils (20 total turns). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/95d8a312-777f-4d6e-bc88-99dfc130ea46/Misplaced+block+-+Coil-to-coil+short+diagram.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Diagram of how current could bypass all turns in Coils 3A and 4A after the coil-to-coil short between their bottom turns. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/7571b436-b861-4b12-a5f5-27e7b52c277a/Overheating+-+before+baffle+damage+-animation.gif Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Rotor was tested over a wide range of loads and the rotor winding was free of turn shorts. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/2354ff69-1c1c-4593-8456-2e920f42982f/Overheating+-+after+baffle+damage+-animation.gif Shorted Turn Theory - Causes of Shorted Turns - Make it stand out About six months after the previous test, rotor vibration and field current both increased significantly. The flux probe test showed at least 30-35 new turn shorts. A failed rotor cooling system created hot spots in the winding that damaged insulation and distorted turns, resulting in many new shorts. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/476cd8e7-acdb-41ad-b268-2c1f7faa346f/coil+to+coil+short%2C+with+burnt+block.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Coil-to-Coil Short: A lead-carbonate film formed over a blocking wedge that allowed significant current to flow between Coils 6A and 7A. The heat burned off over an inch of material from the wedge (right image). The heat burned a large hole in the retaining ring insulation and damaged the top turns of those coils (left image). A coil-to-coil short involving the retaining ring bypassed all 18 turns used in Coil 6A and Coil 7A. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/f4a5fad4-29bd-4148-b5ef-66262c4cf169/LSO%2C+Coil+6A-to-Coil+7A+short.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Lead Slots Overlay Graph - shows Coils 6A and Coil 7A completely shorted out of the rotor winding. Also, note the effect of using magnetic rotor wedges on peak size (Coil 1). Magnetic rotor wedges shunt the magnetic field through themselves and reduce the field the flux probe measures in the air-gap above a magnetic wedge. As a result, peaks from magnetic wedge slots are much smaller than normal. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/0a6c2cb7-4043-49e3-a7cc-1c416b13734d/Rotor+x-section+-+Coil+6A-to-Coil+7A+short.jpg Shorted Turn Theory - Causes of Shorted Turns - Make it stand out Rotor cross-section - shows all 18 turns in Coils 6A and 7A bypassed by a coil-to-coil short involving the top turns of Coils 6A and 7A. Because the bypassed turns were in the two largest coils of Pole A, the temperature-gradient across the rotor body remained modest and vibration remained below trip level. The field increase raised heat production in the coils without turn shorts more than 37.6% above normal levels. https://www.generatortech.com/shorted-turn-theory/shorted-turns-cause-effect-bn9ch monthly 0.5 2025-12-22 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/f5ff1fef-4696-4221-a8d9-7a79f1a91567/Effect+of+TS+placement+on+rotor+bow.jpg Shorted Turn Theory - Effects of Running with Turn Shorts Figure 1 - Rotor bow as function of turn short location The worst location for a turn short is in Coil 1 (left image) since this placement produces the strongest temperature gradient across the rotor and the largest rotor bow. A turn short in one of the largest rotor coils (Coil 5A in this case, right image) produces a small temperature gradient and very little rotor bow. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/cf8488dc-6f33-4348-ba5b-9d72e83b25c0/2-pole+with+no+TS.jpg Shorted Turn Theory - Effects of Running with Turn Shorts Figure 2A - Two-Pole rotor with no turn shorts. The magnetic field around the rotor due to the field current is symmetric. All of the magnetic flux that exits the North pole face will enter the South pole face. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/a16a36f5-9276-4427-95ac-7eeacb6739db/2-pole+with+Coil+3A+TS.jpg Shorted Turn Theory - Effects of Running with Turn Shorts - Make it stand out Figure 2B - Two-Pole Rotor with a Coil 3A turn short The Coil 3A short initially reduces the magnetic field around rotor, but the symmetry of field is not greatly perturbed. The magnetic field strength of the rotor will quickly be restored by the Automatic Voltage Regulator (AVR). The AVR will increase field current until the stator voltage is returned to the set point. Magnetic asymmetry in two-pole rotors is not normally significant enough to cause rotor vibration unless the shorted turn condition is severe and affecting the smaller coils on one pole. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/2582a481-43a4-4c26-af6e-f438826c30b1/4-pole+with+no+TS.jpg Shorted Turn Theory - Effects of Running with Turn Shorts - Make it stand out Figure 2C - Four-Pole rotor with no turn shorts With no shorts, the magnetic field around rotor dure to the field current is symmetric, with flux exiting the two North Poles (A and C) and entering the two South Poles (B and D). Flux from each pole is shared with the two adjacent poles. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/de1486f3-309c-4415-ac64-44c7a5e39d08/4-pole+with+Coil+3A+TS.jpg Shorted Turn Theory - Effects of Running with Turn Shorts - Make it stand out Figure 2D - Four-Pole Rotor with Coil 3A Turn Short The Coil 3A short produce a magnetic field asymmetry, with Pole A’s field being weaker than Pole C. Pole C will pull on the stator core stronger than Pole A, producing a Once/Revolution vibration directly affecting both the rotor and the stator body. The vibration will change instantaneously with changes in field current. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/5cad0e29-1bcd-4f32-bc29-9816759e0fa0/MWS+Load+vs+Field+Currrent+Comparison.jpg Shorted Turn Theory - Effects of Running with Turn Shorts - Make it stand out Whatever it is, the way you tell your story online can make all the difference. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/2fd542ac-bff6-4b2f-999c-254ff52bdf14/Rotor+Cross-section+-+21+TS.jpg Shorted Turn Theory - Effects of Running with Turn Shorts - Make it stand out Whatever it is, the way you tell your story online can make all the difference. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/cca10bee-d1b2-472c-a8ee-faa0382b8298/Visious+Cycle+of+TS+development+-+animation%2C+CR.gif Shorted Turn Theory - Effects of Running with Turn Shorts - Make it stand out Animation of the Turn Shorts Over Time and the corresponding rotor cross-sections shows the locations of the turn shorts detected during each test before the rotor rewind. When the Coil 1B short first developed, it eliminated the vibration due to the Coil 1A short. The Coil 1B short cleared and re-developed. Note how the symmetry of turn short patterns strongly affects vibration. https://www.generatortech.com/shorted-turn-theory/blog-post-three-8mey8 monthly 0.5 2026-03-04 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/94f1bf39-b0a6-4fc2-aefa-926a995be179/Testing+Comparison+Table.jpg Shorted Turn Theory - Benefits of Testing Online and in High-Speed Balance Pits https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/5c8b0aa2-b591-4c60-9090-28b0c6200904/Spin+pit%2C+1250+RPM%2C+no+shorts%2C+CR.jpg Shorted Turn Theory - Benefits of Testing Online and in High-Speed Balance Pits - Make it stand out Case 1A - High Speed Balance Pit Flux Probe Test In balancing pits, flux probe data is often recorded at different rotor speeds. In this example, at 1250 RPM, the rotor was free of turn shorts. At this speed, the compressive force on the coil stacks was not enough to develop any shorts. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/e3065561-a6fc-4428-abc2-4e97a9e31c76/Spin+pit%2C+3600+RPM%2C+3+turn+shorts%2C+CR.jpg Shorted Turn Theory - Benefits of Testing Online and in High-Speed Balance Pits - Make it stand out Case 1 B- High Speed Balance Pit Flux Probe Test At 3600 RPM, three speed-dependent turn shorts were detected. Each turn short developed at a different rotor speed. Tests performed at stand-still would have missed these three shorts. All three speed-dependent shorts were fixed before the rotor was shipped. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/1e96539f-00d6-43be-98b3-efb8d9249689/Impedance+curve+and+Coil+8B+speed-dependent+TS%2C+CR.jpg Shorted Turn Theory - Benefits of Testing Online and in High-Speed Balance Pits - Make it stand out Case 2 - High Speed Balance Pit - Running Impedance and Flux Probe Tests A 60-Hz AC running impedance test showed a short developing as rotor speed rose above 2800-RPM and then clearing when the speed dropped below about 2200-RPM. A spin-pit flux probe test showed the speed-dependent short was located in Coil 8B. The short in Coil 8B was fixed before the rotor was shipped. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/2c5e122d-f9ba-4666-a504-4b1384970ab8/Case+3A+-+3000+RPM%2C+no+TS%2C+CR.jpg Shorted Turn Theory - Benefits of Testing Online and in High-Speed Balance Pits - Make it stand out Case 3A - High Speed Balance Pit Flux Probe Test At 3000 RPM, the rotor winding was free of turn shorts (rated speed was 3600 RPM). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/de7869a7-1c26-449c-9a15-acd573b902af/Case+3B+-+3600+RPM%2C+Speed-depend+TS+in+Coil+6A%2C+CR.jpg Shorted Turn Theory - Benefits of Testing Online and in High-Speed Balance Pits - Make it stand out Case 3B - High Speed Balance Pit Flux Probe Test At 3600 RPM, the rotor developed a speed-dependent short in Coil 6A https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/6c15ec4d-f604-41d1-a49c-26356349db59/Case+3C+-+3600+RPM%2C+Heat+Run%2C+Coil+6A+and+7A+TS%2C+CR.jpg Shorted Turn Theory - Benefits of Testing Online and in High-Speed Balance Pits - Make it stand out Case 3C - High Speed Balance Pit Flux Probe Test After a heat run where the rotor winding was raised to 150 F, the rotor winding developed a temperature-dependent short in Coil 7A when running at 3600-RPM. The Coil 7A short was most likely due to the thermal expansion of the turns . The speed-dependent short in Coil 6A was also detected again. https://www.generatortech.com/shorted-turn-theory/technical-considerations monthly 0.5 2026-03-02 https://www.generatortech.com/shorted-turn-theory/case-studies-fp3ln monthly 0.5 2026-03-04 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/fb9dd101-2a46-457d-844b-d5e37ccb7f76/LSO%2C+F3.0%2C+Coils+3A%2C+3B+and+4B+TS.jpg Shorted Turn Theory - Rapidly Increasing Magnetization (RIM) Waveforms - Make it stand out Figure 1 - Lead Slots Overlay Graph - Online waveform at 15 MWS, 0 MVARS had near optimum detection sensitivity in the #3 coils. The waveform shows a possible symmetrical short condition in the #3 coils, but we couldn’t be sure using just this waveform. A turn short in Coil 4B is evident in this waveform, but lower loads with the FDZC aligned with the #4 coils showed larger turn short indications (not shown). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/fc566cbd-9044-46b2-9ffc-82b32a04f31b/LSO%2C+RIM%2C+Coils+3A%2C+3B+and+4B+TS.jpg Shorted Turn Theory - Rapidly Increasing Magnetization (RIM) Waveforms - Make it stand out Figure 2 - Lead Slots Overlay Graph - RIM waveform recorded during the initial excitation period when the rotor magnetic field was rapidly increasing. The much larger decrease in peak heights in RIM waveforms made the symmetrical shorts in Coils 3A and 3B obvious. The short in Coil 4B shows the same large decrease as the shorts in Coils 3A and 3B. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/e3ebc863-4b7c-47af-a220-130b9d54bfb5/ASO%2C+RIM%2C+Coils+3A%2C+3B+and+4B+TS.jpg Shorted Turn Theory - Rapidly Increasing Magnetization (RIM) Waveforms - Make it stand out Figure 3 -All Slots Overlay Graph -turn shorts in RIM waveforms show equal indications in both the lagging and leading slots (NOTE: curve lines swap colors in the lagging slot region). https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/5aac29f5-401c-40d8-87ff-85ab30468f8d/Four+pole+animation%2C+development+of+Coil+1A+TS.gif Shorted Turn Theory - Rapidly Increasing Magnetization (RIM) Waveforms - Make it stand out Figure 4 - Rotor cross-section animation. The rotor initially had two shorts, with single shorts in Coil 2C and 4A. Being in opposite poles, the magnetic unbalance was very small and vibration was not an issue. In 2009, a new short developed in Coil 1A. With two shorts in Pole A and one in Pole C, the magnetic asymmetry created a vibration issue. After a rotor rewind, the rotor tested short free and had no vibration problems. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/3155783d-ebc1-4353-a74b-ef06aa9cc7e8/ASO%2C+F1.9%2C+4-pole%2C+Coil+1A%2C+2C+and+4A+TS.jpg Shorted Turn Theory - Rapidly Increasing Magnetization (RIM) Waveforms - Make it stand out On-line Near Full Load Waveform- All Slots Overlay Graph - the turn shorts in Coil 1A and Coil 2C are easily detectable in the leading coil slots, but because of magnetic saturation and modulation effects, the short in Coil 4A is not detectable. For the same reasons, none of the shorts are detectable in the lagging coil slots. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/7810d0c0-69a3-4f6d-9387-caf4653ba02f/ASO%2C+RIM%2C+4-pole%2C+Coil+1A%2C+2C+and+4A+TS.jpg Shorted Turn Theory - Rapidly Increasing Magnetization (RIM) Waveforms - Make it stand out RIM Waveform - All Slots Overlay Graph - shows strongly amplified turn short indications in all three coils, with equal detection sensitivity in the leading and lagging slots. This waveform confirmed the location of the three shorts seen in the on-line data, but it cannot be used by itself to quantify the number of shorts in each coil. https://www.generatortech.com/shorted-turn-theory/setting-up-a-shorted-turn-conditionnbspmonitoring-program monthly 0.5 2025-12-18 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/ab1407e5-5c50-4c96-9eb7-e5d67c5b7493/Initial+placement+of+probe.JPG Shorted Turn Theory - Setting Up a Shorted-Turn Condition Monitoring Program - Make it stand out Initial placement of flux probe on stator wedge, Probes are normally installed on the turbine-end of stator, using a 3:00 or 9:00 slot position to accommodate rotor removals and installations. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/82df2e86-2350-4134-b2c4-9fc4f34ef497/Probe+on+wedge+after+cable+is+glued+down.jpg Shorted Turn Theory - Setting Up a Shorted-Turn Condition Monitoring Program - Make it stand out Flux Probe glued and doweled onto stator wedge. The flux probe cable is routed out of the stator core along the wedges, then transitions to a pressure plate between the stator bars get through the stator end-windings. The probe cable is routed to the inside of the the generator casing along solid surface and is then epoxied from start-to-finish. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/f23e23ff-14e3-42d6-a11e-c12d81c113ce/Casing+gland+with+plasitc+PVC+protection+off+and+on.jpg Shorted Turn Theory - Setting Up a Shorted-Turn Condition Monitoring Program - Make it stand out Welded-on casing gland with BNC connection that is suitable for both hydrogen- and air-cooled generators. The flux probe cable is spliced and soldered to the casing gland leads on the inside of the generator. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/9538dfca-99cb-4ab4-a55b-0f57d9a89394/NEMA+4+Box+for+Termination+of+Flux+Probe+-+outside+and+insidejpg.jpg Shorted Turn Theory - Setting Up a Shorted-Turn Condition Monitoring Program - Make it stand out NEMA-4 Termination Box is suitable for air-cooled units. The flux probe cable is connected to the BNC assembly inside this termination box. https://www.generatortech.com/shorted-turn-theory/case-studies monthly 0.5 2026-03-26 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/0a08cb06-cbe4-4c22-99de-cec47f433c4f/Coils+1A%2C+3B+and+6B+TS+Animation.gif Shorted Turn Theory - Case Studies - Make it stand out Lead Slots Overlay Graph Animation - The turn shorts in Coil 1A and Coil 3B are not detectable in the lower load waveforms and the short in Coil 6B is not detectable in the higher load waveforms. The need for recording a wide range of loads is clearly demonstrated. The inset graphs show the same rotor after a rewind successfully repaired all three turn shorts. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/d92338a3-e95a-4816-a6a6-808c1283b634/Coil+8A+TS+and+false+short+animation.gif Shorted Turn Theory - Case Studies - Make it stand out Lead Slots Overlay Graph Animation - shows true and false turn short indication variation with load. At higher loads in this case, false indications in some coils were larger than the indication of the true short in Coil 8B, demonstrating the need to record data over a wide range of loads. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/cd6f600f-132f-4419-88ef-2c9dc315858f/Four+pole+-+Coil+4A+TS+x-section.jpg Shorted Turn Theory - Case Studies Rotor cross-section - showing location of the Coil 4A slots with a single turn short out of 7 total turns. The short created a magnetic asymmetry about the rotor, with Pole C being stronger than Pole A. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/6b8e847a-1a37-4174-a6b8-f96806557267/Four+pole+-+Coil+4A+TS+anim.gif Shorted Turn Theory - Case Studies - Make it stand out Lead Slots Overlay Graph Animation - large nuclear 4-pole generator with a single short in Coil 4-Pole A. The short is not well detectable at high loads, but is easily detectable at low loads. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/2b61b047-38af-46cb-8516-a588aa3ce25b/High+load+before+and+after.jpg Shorted Turn Theory - Case Studies - Make it stand out High Load Data - the Coil 8A turn short was not clearly detectable at high loads. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/1ed8b11f-4cd6-4738-9480-dbdba55328b5/Low+load+before+and+after.jpg Shorted Turn Theory - Case Studies - Make it stand out Low Load Data - clearly shows that the Coil 8A turn short was successfully repaired during the rotor rewind. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/56c57ffb-660d-4b97-953d-672c45034f2f/Rotor+x-section%2C+Coil+6A-Coil+6B+Short.jpg Shorted Turn Theory - Case Studies - Make it stand out Rotor cross-section showing the location of the 58 bypassed turns caused by the coil-to-coil short (29 turns in both Coils 6A and 6B). The short resulted from contact between the top turns of the two #6 rotor coils. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/aeb00410-a554-43dc-86d8-a68585ad96bd/Picture+of+turn+distortion.jpg Shorted Turn Theory - Case Studies - Make it stand out After the retaining rings were removed, the turn distortion responsible for the coil-to-coil short became obvious. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/e93c741d-89fa-4a3c-9beb-76c8e59a5500/Coil+6A-to-Coil+6B+short+anim.gif Shorted Turn Theory - Case Studies - Make it stand out The animation shows the All Slot Overlay Graphs from the test because it clearly show the symmetrical nature of the coil-to-coil short. Even though 58 turns were being bypassed, the high load waveforms were not showing a coil-to-coil short. However, at low loads, the coil-to-coil short was obvious. https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/5e77adc3-76da-43f8-be73-3723f18e0add/Winding+diagram+of+Coil+6A-6B+short.jpg Shorted Turn Theory - Case Studies - Make it stand out A winding diagram indicating current flow shows how contact between the top turns of the #6 coils (red) will allow current to bypass all turns used in those two coils (normal pole-to-pole connector is located between the bottom turns of the two coils). https://www.generatortech.com/about daily 0.75 2025-12-03 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/a782693c-b559-48ac-b334-8713f6547c22/Generatortech+Logo+-+oval+2020%2C+white+on+transparent.gif https://www.generatortech.com/probes daily 0.75 2025-12-12 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/1606511500952-XIN6H9P0ILKFF9ITDWY4/Probe+types+-+Generatortech.jpg https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/68b6537c-42c8-42bc-8bfc-be8941ffb7a5/probe+in+ball+valve+-+closeup3.jpg https://www.generatortech.com/home daily 1.0 2026-04-02 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/a782693c-b559-48ac-b334-8713f6547c22/Generatortech+Logo+-+oval+2020%2C+white+on+transparent.gif https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/1ac19711-6659-4e5e-b398-993c539cd588/Rotor+animation+with+waveform.gif https://www.generatortech.com/history daily 0.75 2025-12-08 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/9a2aa6f0-93d9-48d1-8a17-fad6ff0cdae9/Don+Albright+in+front+of+stator2+-+web.jpg https://www.generatortech.com/contact-us daily 0.75 2025-11-26 https://www.generatortech.com/privacy daily 0.75 2025-12-03 https://www.generatortech.com/service-links daily 0.75 2025-12-03 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/c70ae82f-a723-4ba1-8a42-cee373be2db1/Flux+Pattern+-+2+pole+rotor%2C+transparent.gif https://www.generatortech.com/data-systems daily 0.75 2025-12-03 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/c76c61ba-66c2-4db9-b1b1-7c10b8b60891/portable+system+for+brochure2.jpg https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/05cf4c8b-4db5-46c7-a174-ad4f5adb9cea/G50+Front+View%2C+with+lights+2.jpg https://www.generatortech.com/field-service daily 0.75 2025-12-03 https://images.squarespace-cdn.com/content/v1/5fbda4ac5e8e827d4279354f/f986d1c9-95d3-411d-9027-03ebac6e7f79/typical+installation.jpg https://www.generatortech.com/new-page daily 0.75 2026-02-20 https://www.generatortech.com/navigation-test daily 0.75 2025-12-03