TN33.1003 - Taking Data on Form Wound Rotors and Generators

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Tech Note No. 33 Taking Data On Form-Wound Motors and Generators

(Update - 10/03)

TECH NOTE NO. 33 Reliable Solutions Today!

TAKING DATA ON FORM-WOUND MOTORSAND GENERATORSBy Manuel Garcia, Jr.Consultant, Electrical Rotating MachinesMiami, Florida USA

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To perform a quality rewind on a form-wound, three-phase motor or generator, it is important to take accuratewinding data. Most service centers now purchase form-wound coils rather than making their own, so they can nolonger fine tune winding machine and spreader setups toget coils to fit properly. To hold costs down, assure timelyservice for their customers and obtain coils of the highestquality, service centers must provide coil manufacturers withcomplete, precise winding data with their orders. The fol-lowing procedures explain how to accomplish this, usingEASAs AC Stator Form Coil Data sheet as a guide (seePages 6 and 7).

MEASURING TOOLS REQUIREDThe tools required to take accurate data on form-wound

coils include:

Steel ruler (12 inch or 300 mm) Steel ruler (3 foot or 1 meter) Measuring tape A combination square (12 inch or 300 mm) Adjustable parallels Vernier calipers (6 inch or 150 mm) Set of micrometers (0 to 2 inches or 0 to 100 mm)

Remember that accurate data will enable the coil manu-facturer to provide a set of coils that fit properly the firsttime.

TAKING STATOR DATANote: The following procedures are numbered to corre-

spond with the numbering scheme used on EASAs ACStator Form Coil Data sheet. Perform Steps 1 - 17 beforeburning out or stripping the stator.

1. Core bore diameter. The bore di-ameter is the distance from anypoint on the inside edge of thestator iron to a point diametricallyopposite it (i.e., 180 around theinside of the bore). To measurethis dimension, hold one end of

the tape measure stationary on the inside edge of thebore while scribing a small arc over the opposite in-side edge. Record the largest measurement (to nearest1/16 or 1 mm*).

2. Total core length. This is the length of the iron exclud-ing the finger plates (see No. 6 below). Some of thelaminations on the ends of the core may be damagedor flared, so be sure to take measurements in the bestareas. To assure an accurate dimension (to nearest1/16 or 1 mm), take measurements in several placesaround the core, being careful to measure in a straightline.

Core borediameter

2Total core length

3 Back iron

3. Back iron. This is the distance from the bottom of aslot to the outer edge of the stator iron (near the frame).Measure with the calipers at several locations alongthe length of the slot. If the back iron dimensions vary,record the maximum and minimum dimensions (tonearest 1/16 or 1 mm).

4. Number of vents. Vents are periodic breaks in the sta-tor iron that allow for air circulation. Count and recordthe number of vents.

5. Width of vents. Using a Vernier caliper, measure thewidth of one vent (i.e., the gap between two packs of

* Metric dimensions in this article represent practical tol-erances, not exact equivalents of English units.

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Tech Note No. 33Taking Data On Form-Wound Motors and Generators

(Update - 10/03

lamination). To do so, insert the jaws of the caliper intothe vent and adjust it until the jaws touch the iron onboth sides. Record this dimension (to nearest 1/16 or1 mm). If the vents vary in size, measure each one,indicating the number, width and location of each size.

5 Number and width of vents4 +

6 Finger plate width

6. Finger plate width. Finger plates are pieces of heavymetal that apply pressure to the stator laminations.Using a small ruler or Vernier caliper, measure andrecord the width (depth) of the plate from the end ofthe core (to nearest 1/16 or 1 mm). Do not include anylaminations in the measurement. If the stator has nofinger plates, indicate this on the coil data form.

7Overall coil length

7. Overall coil length. This is the overall length of a coil,measured (to nearest 1/16 or 1 mm) from the outeredge of one knuckle to outer edge of the oppositeknuckle while the coil is still in the stator. Do not in-clude the connection in this measurement.

8. Connection end extension. This is the distance fromthe stator iron to the outer edge of the coil knuckle onthe lead end. To measure this dimension, position thecombination square so that it touches the outside of

8 9

Connection end and opposite connection endextensions

10

11Straight length, top side

Straight length, bottom side

the knuckle, with the ruler facing up and perpendicularto the stator bore. Then lay the 3-foot steel ruler on theiron in the stator bore, extending it out over the coilend far enough to touch the rule on the combinationsquare. Record the dimension (to nearest 1/16 or 1mm). Be sure to measure from the end of the knuckleto the core iron (not to the finger plate).

9. Opposite connection end extension. Follow thesame procedure as above to determine the length ofthe coil extension on the end opposite leads.

10. Straight length, bottom side. The bottom side of thecoil is the one that sits in the bottom of the slot. Todetermine this dimension, place one end of the tapemeasure at the point where the straight edge of thecoil just begins to turn towards the knuckle or diamond.Now measure in the opposite direction along the in-side of the straight part of the coil to the point wherethe coil end starts turning towards the knuckle or dia-mond. Record this dimension (to nearest 1/16 or 1mm).

12 Small knuckle drop

11. Straight length, top side. Using the method describedabove, measure the straight portion of the top side ofthe coil.

12. Small knuckle drop. To determine the small knuckledrop, place the small rule perpendicular to the coil sideat the point where the knuckle (outside round nose)just begins to take shape. Then lay the 3-foot ruleagainst the iron in the stator bore as shown, extendingit over the coil extension to the small ruler. Take thereading (to nearest 1/16 or 1 mm) where the two rul-ers intersect. Measure and record the small knuckledrop on both ends of the coil.

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(Update - 10/03)

13 Large knuckle drop

13. Large knuckle drop. Place the 12-inch combinationsquare under the lowest point of the coil extension withthe rule reaching upward past the coil knuckle towardthe bore. Place the 3-foot rule against the iron in thestator bore, extending it over the coil extension to therule on the combination square. Take the reading (tonearest 1/16 or 1 mm) where the straight edge meetsthe rule. Measure the large knuckle drop on both endsof the coil.

14. Connection end support ring from core. To mea-sure this dimension, place a straight edge on thecenterline of the ring such that it is parallel to the endof the core. Then place the 3-foot ruler against thestraight edge and extend it back to the stator iron. Takethe measurement where the rulers intersect the statoriron. If there are several front support rings, sketch theirlocations on the data sheet and indicate the distanceto each one (to nearest 1/16 or 1 mm).

Connection end and opposite connection endsupport ring

14 15

15. Opposite connection end support ring from core.Follow the same instructions as given above for theconnection end.

16 & 17. Connection end and opposite connection endsupport rings inside diameter. It is often easier tomeasure the inside diameter of a support ring afterthe motor has been stripped. First, make sure the ringis in the proper position. Then hold the end of the tapemeasure against the inside of the ring on one side andextend the tape to the opposite side of the ring. Strikean arc or move tape to several points and measureeach distance. The point on the ring with the largestdiameter is the ID of the ring (to nearest 1/16 or 1mm).

Connection end and opposite connectionend support ring inside diameter 1716

18. Total slot depth. The total slot depth is the distancefrom the top of the tooth to the bottom of the slot. Tomeasure this dimension, insert the depth gauge of theVernier caliper into the center of a slot, pushing theslide down until the gauge touches the bottom. Makesure the top portion of the depth gauge is on top of thestator tooth and record the reading (accuracy .001 or0.03 mm). For accuracy, measure 5 percent of the slots.

19. Slot depth under wedge. This is the area that the coilactually occupies. To measure this dimension, first in-sert a wedge in the wedge groove. Using the insidesection of the Vernier caliper, adjust the jaws so thatthey touch the bottom of the wedge and the bottom ofthe slot. For accuracy, measure and record this dimen-sion for 5 percent of the slots. (accuracy .001 or 0.03mm).

20. Slot width. Using adjustable parallels, select the cor-rect size and loosen the set screw with a smallscrewdriver. Next, insert the parallels into the bottomof the slot and slide the two halves away from each ofother until they fill the width of the slot but can still move.Then tighten the screw and remove the parallels. Toassure accurate measurement, insert the parallels intoseveral different slots. Finally, measure the width ofparallels with a micrometer and record the dimension(accuracy .001 or 0.03 mm).

18

20

19

Slot width

Total slotdepth

Slot depthunder wedge

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(Update - 10/03

21. Lead location. Facing the connection end of the sta-tor, note where the coil leads come out and record thison the data sheet.

A or D Start and finish leads come out of the centerof the coil and the bottom nearest to the sup-port ring.

B or C Start and finish leads come out of the coilconnection end on the top and near the boreand center of the knuckle.

22. Coil type. Face the coil connection. If the top coil sideis on your left, it is a left-hand coil. If the top coil sideis on your right, it is a right-hand coil.

C

Bottom

Right-Hand Coil

B

A

Top

Left-Hand Coil

BottomD

Top

Bottom

21 22+

Coil type

23. Coil lead length and number. Indicate whether theleads come out straight or bend down. Measure andrecord the lengths of both long and short leads fromthe midpoint of the knuckle (to nearest 1/4 or 6 mm).Then count and record the number of coils with onelong lead and the number of coils with two short leads.

24. Jumper. Determine and record the internal connec-tion of the coil group (e.g., 1-4 or 1-7).

25. Connection. Determine and record the connection ofthe stator windings: Wye or Delta.

26. Number of circuits. Determine and record the num-ber of parallel circuits.

23

Leads out

23

Leads down

Long lead

Short lead

Short lead

Long lead

27. Number of slots. Count and record the number of sta-tor slots. This will also be the number of coils neededunless indicated otherwise.

28. Coil throw (pitch). This is the number of slots that acoil spans, counting from the bottom side of a coil tothe top side of the same coil. When counting the coilthrow, be sure to include the slots that actually holdthe bottom and top sides of the coil. (Span is the num-ber of teeth enclosed by the coil.)

1 2 3 4 5 6 7 8

28 Coil throw (pitch)

1 to 8 throw (pitch)

29. Turns per coil. Turns per coil describes the number oftimes the wire is looped in a coil conductor. To deter-mine this, cut through the coil extension of a good coil(near the slot or the knuckle) on end opposite the con-nection and count the wires in the cross section. Thencount the wires in parallel (or in hand) in one of thecoil leads. To get the turns per coil, divide the numberof wires in the cross section by the number of wires inparallel.

Follow the same procedure on several consecutivecoils, since some windings have coils with differentnumbers of turns per coil. (Note: Verify the wire size inthe coils with different turns; the wire sizes in such coilsare sometimes different from the rest.)

Turns per coil = Wires in cross sectionWires is parallel

Turns per coil

2 wires "in hand"11 turns per coil

29

30. Total wires in parallel. The wires brought out togetherin one coil lead are called wires in parallel. Some-times termed wires in hand, these wires are the totalconductors for each turn.

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(Update - 10/03)

31. Wire sizes. Wire size must be determined from thebare copper. Being careful not to distort the wire, re-move all insulation from the portion of each strand tobe measured. Once insulation has been removed, cleanthe copper with steel wool. Now measure the widthand height of each strand with a micrometer (accu-racy .001 or 0.03 mm). Strands are often differentsizes, so measure several strands of the coil and com-pare the dimensions with those obtained from othercoils to assure correct wire size.

32. Strand insulation. Determine which type of insulationis used on the wire and note this on the data form.Examples are glass, film, mica, glass-over-film andbare.

33. Coil weight. Weigh one coil (preferably with the insu-lation removed) and record the weight on the data form.

34. Groups of coils. Determine and record the number ofcoil groups and the number of coils in each group. Notethat with unequal grouping there will be two sets of coilgroups.

35. Iron skew. If the stator slots are not parallel with theshaft, the iron is skewed. To determine the amount anddirection of the skew, place a square of the appropri-ate length in the stator bore, laying it flat against thecore and at right angles to the ends of the bore. Call

Top

Bottom

35 Iron skew

Iron skew

the end where you are standing the Bottom End andthe opposite end the Top End. With the ruled edge ofthe square touching the left inside edge of the chosenslot at the Top End, measure the distance from thesame ruled edge to the left inside edge of the sameslot at the Bottom End (to nearest 1/16 or 1 mm).Record the measurement, noting whether the slots areskewed right or left.

Note: This article was first published in June 2000.

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Please mail or fax a copy to EASA Headquarters, 1331 Baur Blvd., St. Louis, MO 63132; fax (314) 993-2998. Copyright 1998. Version 0902 DP-0902

COMPANY CONTACT DATE JOB #

ADDRESS CITY STATE/PROVINCE ZIP

P. O. BOX PHONE FAX E-MAIL

MFR. HP/KVA/KW POLES RPM FRAME

MODEL VOLTS AMPS HERTZ PHASES

SERIAL # TYPE

C

Bottom

18

20

19

Right-Hand Coil

B

A

Top

Left-Hand Coil

Bottom

3

4

6

1792

10

7

12 816

1314

111

CONNECTIONEND

OPPOSITECONNECTION

END

5

D

Top

Bottom

15

21 22+

23

LEADSDOWN

LEADSOUT

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AC STATOR FORM COIL DATA

COMMENTS

1 CORE BORE DIAMETER

2 TOTAL CORE LENGTH

3 BACK IRON

4 NO. OF VENTS

5 WIDTH OF VENT(S)

6 FINGER PLATE WIDTH

7 OVERALL COIL LENGTH

8 CONN. END EXTENSION

9 OPP. CONN. END EXTENSION

10 STRAIGHT LENGTH, BOTTOM SIDE

11 STRAIGHT LENGTH, TOP SIDE

12 SMALL KNUCKLE DROP CE _____ OCE _____

13 LARGE KNUCKLE DROP CE _____ OCE _____

14 CONN. SUPPORT RING FROM CORE

15 OPP. CONN. SUPP. RING FROM CORE

16 CONN SUPPORT RING I. D.

17 OPP. CONN. SUPPORT RING I. D.

18 TOTAL SLOT DEPTH

19 SLOT DEPTH UNDER WEDGE

20 SLOT WIDTH

21 LEAD LOCATION A B C D22 COIL TYPE LEFT-HAND RIGHT-HAND23 COIL LEADS LONG # ______ LG ______

SHORT # ______ LG ______

OUT DOWN24 JUMPER (1 - 4 OR 1 - 7) 1 -

25 CONNECTION (WYE OR DELTA)

26 NO. OF CIRCUITS

27 NO. OF SLOTS

28 COIL THROW 1 -

29 TURNS PER COIL

30 TOTAL WIRES IN PARALLEL

31 BARE WIRE SIZES ( ) X

( ) X

32 STRAND INSULATION

FILM GLASS MICA BARE OTHER33 COIL WEIGHT LBS.

34 ___________ GROUPS OF __________ COILS

___________ GROUPS OF __________ COILS

35 IRON SKEWED RIGHT LEFT _______ IN.

SPECIAL FEATURES YES NO

DATA CHANGE

COIL SUPPORT RING STEEL

TERRACE WOUND

CORONA PROTECTION

RTDs

OHMS QTY

HERMETIC

SLOT PAPER USED

INSULATION CLASS B F H VPI DIP & BAKE SEALED LEADS TAPED LEADS SLEEVED

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(Update - 10/03)

Copyright 1998. Version 0902 DP-0902

GENERAL

All dimensions should be taken to the nearest 1/16 (1 mm) except18, 19, 20 and 31, which should be to the nearest .001 (0.03 mm),and 23, which should be to the nearest 1/4 (6 mm).

All items must be completed unless otherwise explained.

To make the data easier to read when the form is transmitted viafacsimile machine, use only a blue or black felt or nylon tip pen.Please press heavily and record the data in the answer column pro-vided.

1 Core Bore DiameterInside diameter of the stator iron. This is mea-sured from tooth to tooth through the center line of the machine.

2 Total Core LengthLength of the stator iron including vents butexcluding finger plates. Please make several measurements andgive the average.

3 Back IronThe distance from the outer edge of the stator iron nearthe frame to the bottom of the slot.

4 No. of VentsThe number of vents in the stator iron.

5 Width of a Vent

6 Finger Plate WidthWhen present, give the width of the plate thatapplies pressure to the stator laminations.

7 Overall Coil LengthThe overall insulated coil length measuredfrom the outer edge of one coil knuckle to the outer edge of theother knuckle.

8 Connection End ExtensionThe coil extension measured from theouter edge of the coil knuckle to the stator iron on the lead end.

9 Opposite Connection End ExtensionThe coil extension mea-sured from the outer edge of the coil knuckle to the stator iron oppo-site the lead end.

10 Straight Length, Bottom SideThe length of the straight portionof the coil in the bottom of the slot. This is measured along theinside edge of the coil from point to point where the diamonds justbegin to form.

11 Straight Length, Top SideThe length of the straight portion of thecoil in the top of the slot. See Item 10 for details.

12 Small Knuckle DropWhen extending a straight edge across thestator iron and out over the coil extension, the distance from thebottom of the straight edge to the area of the coil where the knucklestarts to form. Measure on both ends.

13 Large Knuckle DropWhen extending a straight edge across thestator iron and out over the coil extension, the distance from thebottom of straight edge to the lowest point of the coil knuckle whereit touches the support ring. Measure on both ends.

14 Connection End Support Ring from CoreThe distance from theinside edge of the insulated front support ring to the stator iron onthe lead end. If there is more than one ring on each end, note thenumber of rings and the distance between rings. Allow for ring insu-lation if it is not present when the measurements are made.

15 Opposite Connection End Support Ring from CoreThe distancefrom the inside edge of the insulated support ring to the stator ironon the opposite lead end. See Item 14 for details.

16 Connection End Support Ring Inside DiameterThe inside di-ameter of the insulated support ring on the lead end. Scribe an arcfrom the inner edge of the ring to the opposite inner edge and takethe largest measurement.

17 Opposite Connection End Support Ring Inside DiameterTheinside diameter of the insulated support ring on the opposite leadend. See Item 16 for details.

18 Total Slot DepthThe total slot depth of the stator slot measuredfrom the top of the tooth to the bottom of the slot.

19 Slot Depth Under WedgeThe distance from the bottom of theslot to the bottom of the wedge groove.

20 Slot WidthThe stator slot width measured at the bottom of theslot.

21 Lead LocationChoose one letter (A, B, C or D) to indicate whichlead arrangement is applicable.

22 Coil TypeIndicate the type of coil desired, either left-hand or right-hand. Looking from the connection end of the coil, is the right-handslot section of the coil in the top or bottom of the slot?

23 Coil Lead Length and NumberBoth long and short leads. Indi-cate if leads are down (i.e., perpendicular to the length of the coil)or straight out.

24 JumperThe internal connection of the coil group.

25 ConnectionThe connection of the stator windings: Wye or Delta.

26 No. of CircuitsNumber of parallel circuits.

27 No. of SlotsThe number of stator slots. This is also the number ofcoils unless otherwise advised.

28 Coil ThrowThe span of the stator coil. The slot that holds the bot-tom coil side is Slot #1.

29 Turns per CoilThe number of turns that the coil conductor(s) is(are) looped. Count turns on the opposite connection end.

30 Total Wires in ParallelThe number of wires in parallel. This iseasily indicated by the number of wires that make up one of the coilleads.

31 Wire SizesThis measurement is taken on the bare copper. If morethan one wire size is used, please indicate these sizes as well.

32 Strand InsulationWire insulation type. Examples are: glass, film,mica, glass over film, and bare.

33 Coil WeightThe weight of the one coil, preferably with the insula-tion removed.

34 Groups of CoilsNumber of coil groups and the number of coils ineach group.

35 Iron Skewed?If the stator slots are skewed, measure the offset ininches.

INSTRUCTIONS

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(Update - 10/03Copyright 2003Reliable Solutions Today!Version 600DP5M-1003

Electrical Apparatus Service Association, Inc.1331 Baur Boulevard St. Louis, MO 63132 U.S.A. (314) 993-2220 Fax (314) 993-1269 www.easa.comEA SA

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Documents

TN33.1003 - Taking Data on Form Wound Rotors and Generators