Introduction. 1. PMG scheme. Permanent magnet generator consists of the following:

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2 Introduction This manual focuses on describing the process of building a permanent magnet generator (PMG) in an elaborative manner. PMG can also be referred to as an alternator as it functions towards generating alternating current (AC). It will not generate utility power or mains voltage but generates low voltage or three phase AC & converts it into direct current or (DC) to facilitate charging of a 12 volt battery. 1. PMG scheme Permanent magnet generator consists of the following: - A steel spine - A steel shaft - A stator with coils of wire - Two magnet rotors - A rectifier. 2

3 Stator The stator accommodates six coils of copper wire. These are cast in fiber glass resin. The casting is mounted on to the spine to prevent it from moving. Rectifier It changes the AC to DC in order to facilitate battery charging. It is mounted on an aluminum heat sink. This helps in keeping it cool. Magnet rotors These are mounted on bearings & turn on the shaft. The rear rotor is situated behind the stator. The front rotor is situated on the outside & fixed to the rear one with the help of long studs that pass through a hole in to the stator. The wind turbine rotor blades would be fixed on to the same studs. These function towards turning the magnet rotors & move magnets past the coils. The magnetic flux passes from rotor to rotor with the help of stator. Electric power is is actually produced by this moving magnetic flux. Construction of PMG This manual focuses on detailed description of how to build the PMG. Going through this process prior to building PMG will be of great help. Captures 2 is information based on the list of materials & tools required for building the PMG. Chapter 3 elaborates the process of building of special tools or jigs and moulds required for PMG construction. It is possible to build more than one PMG with these tools & moulds. Chapter 4 focuses on the stator. It describes the process of winding the enameled copper wire coils & casting them in resin via using jigs and moulds. Chapter 5 elucidates the process of building of magnet rotors via using magnet blocks in conjunction with steel disks set in different resin casting. Chapter 6 emphasizes on the process of assembling of the parts in to a whole PMG. It also describes the process of building of the mechanical parts, rotors balancing mechanism and specific requirements for connecting the wiring from the stator. 3

4 Chapter 7 is about testing of PMG. It consists of the procedures related to checking of correct balancing of PMG & its usage. It also describes various options for connection of electrical output. It also elucidates the process of connection of the PMG to the battery. Chapter 8 provides additional information on the usage of polyester resins and usage of PMG for hydro power. Benefits of PMG PMG is specially designed for small wind generators. If you want to build a complete wind generator, you would also require the following. (1). A tower or a steel pip supported with guy ropes. (II). A yaw head swiveling on the tower top. (III). A tail in order to keep it facing towards the wind. (IV). A set of blades in order to turn it. The PMG spine bolts on to the yaw head. The assembly of blade fits on to the front part of the PMG. The yaw head & fail is required to be constructed in a manner to let the wind generator turn from strong winds & enjoy self protection. 2. Wind turbine 4

5 Chapter-2 List of tools & materials The PMG functions well at low rotational speed. It works towards generating 180 watts at 420 rpm. This is equivalent to 15 amps at 12 volts. The PMG can easily generate more power at higher speed. However, high currents can be a cause of heated coils which decreases the efficiency of the PMG. It would be great to change the stator coils for higher speed. These can be changed via utilizing different size wire or altering the way in which they are connected. Usage of thicker wire is better for using PMG at higher speeds. Thicker wire is capable of carrying more current without getting excessively heater up. The wire also results in fewer turns on the coils which indicate that the PMG will not function at low speed. Changing the connections will let you utilize the same PMG for 10 was well as high speeds. These connections can be changed is two different ways. This is described in chapter 7. Precautions to take It is recommended to take special care during the construction & assembling of PMG. This will avoid magnets coming loose which happens under extreme conditions. The rubbing of loose magnets on the strator can damage PMG. - Follow the instructions for casting the magnet rotors carefully. - Avoid hitting the magnet rotors with hammers when assembling the parts. - There should be at least 1 mm gap clearance between the strator & the magnets on both sides. You can go for larger gap for higher speed or heavy duty usage. - Make sure you do not run the PMG at speeds faster than 800 rpm on a wind turbine. - Strictly avoid mounting the rotor blade assembly directly on the front magnet rotor disk also avoid the assembly at any point away from the studs. Just mount the rotor blade on to the studs & nuts them selves, which come through the disk. - Make sure that the box section spine of the PMG is vertically upright when mounting the PMG on the wind turbine yaw mount. 5

6 Materials & tools required for building PMG I. Fiber glass supplies. II. Polyester resin premixed grams III. Catalyst (peroxide)- 50 grams IV. Talcum filler powder grams V. Fiber glass mat (1 ounce/ square foot)- 300 grams VI. Coloring pigment resin- 50 grams VII. Putty or plasticene VIII. Stainless steel wire- 200 grams IX. Grade 3 ferrite magnet blocks (pre magnetized) grams X. Enameled winding wire grams. XI. Flexible wire XII. Solder & s leaving for connections XIII. Y2 inch masking tape XIV. Bridge rectifiers. XV. Heat sink for rectifiers- 250 grams XVI. Box section tube (RHS) for spire grams. XVII. Magnet disk or octagonal plates grams. XVIII. 10 mm threaded rod (studding) grams. XIX. 10 mm nuts- 300 grams. XX. 10 mm washers XXI. 8 mm threaded rod- 125 grams. XXII. 8 mm nuts- 50 grams. XXIII. 5 mm nuts & both for rectifiers XXIV. Shaft- 500 grams Materials required for moulds & jigs - Composite floorboards - Wood glue - Sand paper - Wax polish - Polyurethane varnish - PVA releases agent - Paint brushes - Thinners - 13mm plywood - Formers - Stator mould centre - Steel rod/ pipe - Small pieces of steel plate/ thick sheet metal - 2 bolts with butterfly nuts measuring 6 mm diameter & 60 mm in length. - 4 bolts measuring 10 mm in diameter and 25 mm in length. - 1 bolt measuring 12mm in diameter and 150 mm in length. 6

7 Essential tools - Safety goggles - Face mask - Gloves - Workbench with vice welder - Angle grinder - Hack saw - Hammer - Punch - Chisel - Compasses - Tape measure - Angle gauge - Two spanners measuring - Angle gauge - Two spanners measuring 8,10,13,17 & 19 mm each. - Tap wrench - M 10 taps - Brass wire - Pillar drill press - Drill bits measuring 6,8,10, & 12mm - Hole saws measuring 25mm & 65 mm - Wood lathe - Chisel for wood lathe - Jigsaw for cutting wood - Scales - Dispenser - Plastic buckets - Scissors - Wire cutters - Sharp knife - Soldering iron - Resin cored solder. 7

8 Chapter: 3 All about jigs & moulds Acquiring knowledge about making jigs & moulds is necessary for building PMG. These jigs can be reused to build more PMGS as desired. Coil winding machine 4. The coil The stator of PMG consists of 6 copper wire coils. The coils are wound on plywood coil-former. The former is monted on the crankshaft end between cheek pieces. You need to create a crankshaft turned by a handle as described in the diagram 5 given below. 5. Crankshaft 8

9 Cut a small flat steel plate measuring 60x30x6mm. Fix & weld it toward the crankshaft end as shown in diagram6. 6.Steel plate Cut out three pieces of plywood measuring 13mm each as illustrated in diagram7. 7. Coil former and cheek The coil former measures 50mmx50mx13 thick. It consists of rounded corners. The 2 cheek pieces measures 125mmx125mm & there are 20mm wide notches top & bottom in each. The notches help in securing masking tape under the coil to tape up prior to removing it from the notches. Stack the cheek pieces with the notches in line. Drill holes for mounting bolts. These holes should be 16mm in diameter & at least 40mm apart. You need to make use of a drill press in order to drill the holes square to the plywood. 9

10 8. Drilling the holes (stack three pieces like this) Focus on passing 2 bolts through the holes in the flat plate. Also past bolt on cheek pies with coil former in between. Try using butterfly nuts. 9. Fitting coil former and cheek pieces 10

11 Jigs for the rotors The magnet rotors are securely mounted on a fearing hub. The hub consists of a flange. This flange has holes in it. The number holes in it. The number of holes and the diameter will depend on the type of hub you decide on. Here, we are focusing on an arrangement of 102mm PCD. The PCD jig will be utilized to drill holes in the rotors & balancing them. It is important to mark & drill accurately. 10. PCD bearing hub - You need to cut out a square piece of steel plate measuring 125mmx125mm. - Draw diagonal lines between the corners. You need to mark the precise centre with a punch. - The compasses need to be set at 51 mm radius. - Draw a circle. - The circle diameter is the PCD of the holes present in the hub. - Focus on punching both places where one line meets the circle. - Set compasses at 72mm. - Make sure you mark 2 points at 72mm distance from the first two present on the circle. - Drill 4 holes at 72mm apart on the circle. You need to use a small drill initially & then a larger one. 11

12 11. Drilling the PCD jig Magnet positioning jig This jig helps in placing all the magnet blocks at correct places on the steel disks. Remember, that just one jig is required. You need to create the jig from a 250x250mm aluminum sheet or plywood. 12. Magnet positioning jig - Mark the central position of the work piece. - Now draw 3 circles consisting of diameters 50mm, 102mm & 200mm on the marked centre. - You need to draw pair parallel straight lines as tangents to the 50mm circle. - Draw 3 additional Paris of straight lines at 45 & 90 degree angles to the first Pair. 12

13 - Mark the magnet positions via using these parallel lines. - Cut out the jig along the bold lines. - You need to draw a line that connects 2 opposite magnet centers. - Place the PCD jig on the top of the circle measuring 102mm circle in line with the magnet centers. - Drill 4 holes. These holes should match the 4 holes on the steel disks perfectly. How to make moulds Moulds are very important for the strator & rotor castings. These can be easily turned from aluminum or wood. There is another method wherein you can create clay plugs on a wheel. The shape of the plug will be the shape of the outer portion of the strator. Now create a fiberglass mould on the plug. Make sure that surface of the moulds is flat. The moulds need to be very sturdy & smooth. Remember that the stator casting cannot be separated from the moulds easily. You would require hammer btous. Here is a description of one method of creating moulds from composite wooden floorboard sheets via utilizing wood turning. Stator outer mould 13. Disk - You require cutting out many disks of flooring sheet of about 500mm diameter. - Take all learning one of the disks & cut circular hole in each. The hole should be approximately 360mm in diameter. This process will form many rings. - Now draw a circle measuring 360mm diameter on the disk that was left out initially. - The centre of this disk should be drilled with a 12mm hole in order to facilitate with centering. - All the rings need to be glued on top of the remaining disk. This will create as tack with a hole measuring 60mm deep. You need to use loads of glue on the insides of the rings. 13

14 14. Ring - A small disk of 15mm plywood needs to be cut out. The disk should be around 140mm in diameter. New drill a hole measuring 12mm towards its centre. - Glue the small disk in to the centre of the hollow via placing a 12mm bolt. The edge of the disk must be laced with a lot of glue. - Make sure you mount another piece of wood or board on the lathe & a motor or the wheel hub of a vehicle. This will be the faceplate. - You must spin the faceplate & utilize a pencil in order to create small circle towards the centre. - Drill a 12mm hole at the centre & hold the drill parallel to the shaft. 15. Stack - The glue stack needs to be screwed on to the faceplate via using a 12mm bolt to centre it. You need to utilize 4 wooden screws through the disk & in to the faceplate. - Make sure the face of the mould runs well. You may also try this via holding a pencil & closing it when it spines. - The face is high just where the pencil makes marks. Now loosen the screws & insert paper pieces between the faceplate $ the stack on the opposite side from the pencil marks. Now tighten the screws & check. 14

15 16. Turning the mould Now you can easily give shape to the mould with a chisel. Put on a mask to cover your mouth. This will avoid inhaling dust. Do not wear loose clothing as these can get caught in the rotating mould. - Cut a smooth surface towards inner stack edges. - The surface must taper at about 7 degrees. - The diameter of the outer edge must measure 380mm. - The flat face diameter should be 360mm. - The corner inside need to be smooth with slight radius. 15

16 17. Shape of the stator mould - You must turn the inner disk down to about 130mm diameter of the face with the help of a taper. The corner needs to be rounded. 18. Center disk - Now place a coil against mould face check if it fits properly. In case, not then either the centre disk is smaller or the hollow is a little larger. Remember that the centre of the coil needs to be at 250mm from the centre of the mould. - Remove the mould from the motor or lathe. 16

17 19. Holes in the mould - Drill 4 holes in the central portion. These holes are used to separate moulds. Small plywood pieces must be screwed on the underside of mould. This helps in creating feet. Stator inner mould - Cut out disks measuring 370mm in diameter. - At the centre of each disk, drill a 12mm hole. 20. Inner mould 17

18 - Glue these disks into a stack via using a bolt measuring 12mm at the centre. This stack needs to be at least 45mm thick. - Now turn a 20 degree taper on the rim. Round off the corner to reduce the diameter from 368mm to 325mm. - The outer mould must fit properly over the inner mould. The gap between the two must be about 6mm around the edge. Also remove the inner mould from the face plate. - Draw two lines on the larger face of the mould. - Cut out 2 flat faces as shown in diagram Cutting faces. Inear Electrical testing - These faces are meant to build a thick casting around the mounting studs. 18

19 Magnet rotor moulds The PMG requires 2 magnet rotors. Usually one mould will make it function well but two moulds can make the production easier & two rotors can be efficiently produced at one time. The outer mould is quite similar to the stator outer mold but simpler in design as depicted in diagram Rotor mould The PCG jig must be utilized to drill 4 holes that match the holes in magnet disks. An inner disk mould is necessary for each magnet rotor. The disk needs to carry the same pattern of 4 holes. 23. Magnet rotor. Inner disks All moulds are sanded down to a smooth surface. These are given a final finishing touch with wax polish and varnish. Avoid using ordinary paint on the moulds. The resin process will make the paints wrinkle and spoil the whole appearance of casting. Jigs for the stator Stator studs jig Four 8mm supporting studs must be properly cast in to the stator. A jig is also required to hold these studs in place until the resin is set. This jig is constructed from wood measurement must be accurate otherwise the studs cannot be fit in to the spine in the later stages. 19

20 - At first, create a punch mark at the centre of the largest face. - Mark arcs at a radius of 178mm from the punch mark via using compasses and dividers. - Punch 4 marks on these racks. These. These marks must be 30mm apart & 10mm from the edge. - Using an 8mm drill, make a hole. A drill press will provide accurately square holes. Refer to the diagram 24 to get a better understanding of the whole procedure. 24. Stator studs jig 20

21 Paper temp later. Chopped strand mat (CSM) made of fiber glass is used in the stator. You can easily lay the template on CSM later. Use a felt pen to draw around them. Cut the pieces out. Refer to the diagram Paper templates for CSM 21

22 Chapter: 4 Construction of stator This chapter focuses on how to build a stator via using jigs & moulds. It would be great to wind a coil prior to making the stator moulds. This will help in easy checking of mould for proper fit. Winding the coils - Mount the winding wire reel on an axle behind you aligned with coil former. The wire must form an s shaped bend as it winds on to the coil. See the diagram Correct and incorrect wire feed - Bend the tail of wire 90 degrees at a point 100mm from the end. Avoid handling the bend on any other part of the wire. Just leave it straight. Remember that bent wire does not create a compact coil. - Place this bend in the notch in a way that the tail hangs out. - Twist the tail loosely around a butterfly bolt. - Focus on gripping the wire between the reel & the winder in a piece of rag. This will help in keeping it tight. - Wind the crankshaft handle carefully. The first turn lies secure against the cheek piece on the side just where the tail come out. The other turns lie against each other in a neat form. There is no crossing over between the turns. You need to build the coil in even layers. You need to count the number of turns carefully. These will. - Once the coil is complete pass a sticky tape piece just under the coil on both sides. Bind it in a tight manner. Avoid cutting off the winding wire until it is done or the coil may spring out & loosen. You need to cut the wire tail 100mm away from the coil. - Remove the coil from the tail & wind 5 more coils in the similar manner. 22

23 - Place the coils on a table to make them exactly the same way up. Refer to diagram 27. The starting tail must be on the upper surface. Make sure it is n to hidden under the coil. 27. Coils must be the same way-up - Allot numbers to the coils as 1-6.Write the numbers on a masking tape. - You need to scrape the enamel off the last 20mm of each tail of enameled wire. Do it until it attains bright copper texture. Using a hacksaw blade will be ideal especially when the edge is sharpened with a grinder. - Solder flexible wire tails as shown in diagram Soldering the tails 23

24 The lengths of flexible tails should be as mentioned below: Coils 1 & 6- Coils 2 & 5- Coils 3 & 4-800mm flex 600mm flex 400mm flex. - You need to cover the soldered joints with cleaning. Make sure you do not leave bare copper. - Label all the tails with coil number in conjunction with letter A or B. A is for the coil start point & B is for coil finish. Make sure you do not mix these up. You may use 2 colors, namely black flex for the starts & white for the finishes. - You need to lay the coil out in the outer mould. - Check carefully that these fit comfortably & the tails are long. The tails should remain within the mould until the exit point between the coils 3 & 4. make doubly sure that all the coils are laid the same way up. 29. The coils in mould 24

25 How to prepare for stator casting The stator casting will consist of the following: I. Six coils II. Polyester resin III. Talcum powder IV. Pigment V. Fiberglass mat (CSM) VI. 4 threaded rod studs. Measuring 8mmx100mm. Make doubly sure that the moulds are prepared in a proper manner. Focus on sanding, sealing and polishing them properly. In case, PVA release is available use it. Use templates and cut out fiberglass CSM pieces. You will get two circular disks for laying flat in the outer mould. Curved the inner portion of the outer mould in a double CSM thickness. Overlap 23mm between pieces. Once you are sure that you have all in hand, initiate the process of resin casting. It is a fabulous idea to read through the whole procedure initially. Make sure you understand it prior to starting. The process of stator casting The diagram 30 show below describe the process for weighing out the resin & talcum powder. The talcum powder is used only for bulk nixes. This will prevent over heating & thicken the mix. Different weights are used for different mixes. You need to follow all the instructions step by step. 30. Mixing polyester 25

26 Step one Mix resin with catalyst slowly so that there is no churning in air bubbles. If you want to add talcum powder, do it only once the catalyst is mixed. Once the resin is mixed used it immediately. It will heat up and begin to set once it remains in the mixing bucket for a few minutes. Step two Use the correct amount of catalyst. Remember that resin requires less catalyst as compared to normal fiberglass work. Put in less catalyst once the works shop is hot. Step three Do not wipe the polish off the mould with brash strokes. Use a prodding action with the resin. Step four Place the outer mould on a news paper spread on a work bench. Step five Mix about 200 grams of resin with 3cc of catalyst. Do not use talcum powder in the first two mixes. Step six You need to paints resin all over the inner side of the outer mould. Avoid painting on top of the island. Step seven Just apply a single layer of fiberglass mat (CSM). Pain some more resin over it, use poking motion to eliminate bubbles. You need to work the resin in to CSM. Step eight Now apply a second layer of CSM to the wall. Keep one disk for later. Step nine Put the coils in to the mould. The wire tails come out in one place between coils 3 & 4. 26

27 Step ten Mix another 100 grams of resin with 2cc catalyst. You need to pour this over coils wires in order to let soak in strictly avoid making pools of resin. Step eleven Make a mixture of 600 grams of resin with 9cc catalyst & 600 grams of talcum powder. Pour the mixture in to spaces available between the coils. Step twelve Remove air bubbles via shaking the mould vigorously. Resin gets settled with the help of vibration & rotary motion. Step thirteen Make a mixture out of 200 grams resin, 100 grams of talk & 3cc catalyst. Put the second CSM disk over the coils. Now paint it with these mixtures. Use thinners &wash out the paint brush thoroughly. Step fourteen Place the inner mould down in the outer mould. Fit the 12 mm bolt through the centre of both the moulds. You need to tuck space between the moulds. A flat spot on the inner mould settles over the portion where the wires emerge out of stator. The resin is helpful in rising up the sides. Step fifteen Pour resin gently in to the gap available between the moulds until it rises to near the top of the female mould. Create a mixture of 100 grams of resin with 1.5cc of catalyst. Step sixteen You need to place the jig over the mould as shown in diagram 24. One end of the mould should be over the tails of wire. Step seventeen Tighten 12mm bolt with a nut. You need to insert 48mm stud in to the holes. The nuts should be on top. Immerse the studs in resin for half of their length. The process of casting is now accomplished. It will become warm & harden with some hours. Place it in a warm place in case, it does not begin to set in a few hours. 27

28 Once the resin is hardened, eliminate the casting from the mould. Exercise patience. Separate jig from the studs. You need to tap the two moulds apart via utilizing a bolt in each hole around the central hole. Also knock the casting out of the outer mould via turning it over. 31. Stator elements 28

29 Chapter 5 How to build Rotor The magnet rotor can also be referred to as casting. You also require following a procedure for assembling parts. First, focus on collecting all the magnet blocks, magnet plates, stainless wire rope etc. together. Magnet Plates: Each magnet rotor is built on a stainless 6mm steel disk. Avoid using aluminum or stainless steel for the disk. It is crucial for these disks to be made of magnetic material. The disk contains holes in order to mount it to the hub. Here we will have 4 holes each of 10mm in diameter on a circle at 4 inches PCD. In case, you choose a different hub, then moulds and jigs need to match this hub. There is a hole at the centre of the disk measuring 65mm diameter. Four hoes need to be taped and drilled for M10 rod between the magnet positions at 220mm PCD. You must screw 4 pieces of M10 rod, 20mm long in to these holes. These will easily bind to the resin and facilitate better holding of the casting on to the disk. 32. Magnet rotor disc. Make sure that the magnet plates are flat and not warped. It is not very possible to cut the outer circle without plate warping. Another method can be utilized to build the rotor disk. You need to cut a square and then draw circle on it. Now cut off the corners at 45 degrees. Make sure that the length of each edge is about 116mm. 29

30 33. Alternative shape of an octagon The magnets will be positioned on the octagon corners. The hole at the centre is made with the help of a hole-saw. Grind the steel disks until they are clean and bright. This should be done just before putting them in the mould for casting of resin. You must remove grease carefully with spirits. Magnet Blocks: There are about eight magnet blocks on each rotor. Each block consists of a north pole and a south pole as depicted in diagram Poles of the magnets You need to take special care while magnet handling. This is because magnets can result in damage of music tapes, floppy disks, credit cards and other types of magnetic media. Separate these magnets from each other via sliding them sideways. They can attract each other through strong forces. You must provide extra attention on not to let them fly together. Strictly avoid using hammer to assemble the PMG. The magnet blocks on the disk need to display alternate N-S-N-S on the top faces. You can check whether the procedure you are carrying out is correct wherein you need to hold the magnet each time it is placed in a way that it repels the one before as shown in the diagram

31 35. Placing the magnets Now place it without turning it over. Check with another magnet when they are all in. It will be attracted, repelled, attracted, and repelled by each magnet in the circle. It is important for the two magnets to attract each other once the mounting holes are lined up. Check thoroughly that the magnets next to the holes on one rotor are dissimilar from the ones present on the other rotor. 36. These rotors are not the same Stainless Steel Wire: The magnets will try to fly off the rotors while the PMG turns. Embed the magnets in the resin casting. Remember that the resin alone is not capable of holding the magnets. The resin need to be reinforced via warping wire around outside of the magnet rotors in order to hold the magnets in. Steel wires are strong but can take the magnetism from the magnet blocks. Use stainless steel to avoid any damage on the magnet. Assemble all the parts dry prior to using any resin. You must put the stainless steel rope around outside the magnet at least 5 times. Cut it off with a grinder or chisel. Now tape it in several places to keep it in a coil. Now the magnet is ready to drop in to other places. 31

32 The Rotor Casting Formula: Prior to starting, check that everything is ready. Things should be as mentioned below: The moulds are fully prepared with release agent or polish. The magnets in conjunction with the magnet disks are clean and bright without any traces of grease. Sixteen strips of CSM are ready to fit between the magnets. The wire made of stainless steel is cut to length and taped. The magnet positioning jig is ready. 37. Magnet rotor mould assembly Place 4 bolts through the holes in the holes in the outer mould. You need to lay a steel disk in the outer mould. Now place the inner mould on top. Make sure the taper and place the smaller face down so that it can be eliminated easily after casting. Make a mixture of 200 grams of resin with 3cc catalyst. Paint it all over the disk. Put in 20 grams of pigment if required. Also mix 100 grams of talcum powder with the rest of the resin. Pour the mixture around the disk edge until it fills the gap. Lastly level it with steel disk top. Position the magnet positioning jig on the bolts. Place the blocks of magnet on the steel disk inside the positioning jig. Take special care that the magnetic poles alternate as north, south, north, south. Prior to placing the magnet on the disk. Once all the magnets are in, just remove the positioning jig. Utilize this for the two rotors attract each other. 32

33 Fit nuts to the 4 bolts and tighten the central disk on to the steel disk. Create a mixture of 500 grams of resin and 7cc of catalyst. Now add 300 grams of talcum powder. Arrange small strips of CSM between the magnets and into the gap at the edge. Add resin until the CSM is soaked. Poke it or vibrate it to remove bubbles. Arrange the stainless steel wire loosely around the outside of the magnets. Lets it sit on the CSM. You need to take special care that the magnets do not move around. Create a mixture of 500 grams of resin and 7cc of catalyst. Again add 300 grams of talcum powder. You must fill the spaces between the magnets until the mixture of resin reaches mould top. The rotor castings must be left undisturbed for several hours to set hard prior to removing them from the moulds. Exercise plenty of patience when separating the rotors from the moulds. Do not use violent hammer blows which may risk them. Take special care the mould and not the rotor. Assembly Chapter 6 Rotor Balancing: Each rotor should be in a placed in a proper balanced position. In case you do not take care on this the PMG will shake when it is turning. The whole PMG needs to be balanced again at the end as the rotors may not be mounted in the central position as required. The final balancing is carried out by a different procedure. 38. The balancing jig and spike The first step to balance a magnet rotor is to attach the PCD jig via using 4 bolts. Balance the rotor accurately on the spike as shown in the diagram 38. If you see the rotor sitting in level, it is balanced 33

34 properly. If this is not the case, you require adding small weights to it. You may even drill out some of the resin between magnets until it sits in a leveled position. Turn the PCD jig around on the rotor. Check again. Also replace any weights with M10 threaded rod pieces. These rod pieces should be screwed in to holes in the resin between the magnets. PMG Spine and Bearing Hub: Create a spine of PMG via using a 380mm long box section tube measuring 50x25x4mm. You need to mark the exact centre of a large face and mark four 8mm holes. You may utilize the stator studs jig to facilitate drilling of the holes. The central hole is 25mm. Use a saw to drill this hole. Now weld the shaft in the 25mm hole. Take special care to hold the shaft as square as possible towards the spine while welding it. 39. The box section The bearing hub perfectly fits on the shaft. It also consists of 50x25 mm deep groove ballraces in it. It also has a spacer between them A plastic cap is required over the end in order to keep the dirt away from the bearings. 34

35 40. The bearing hub Greasing the bearings is very important. You must pack them within grease half of their circumference. Do not cover them with grease fully. Final assembly of PMG: Step one: Cut about four pieces of M10 threaded rod. These rods must be 200 inches long. They are better used as studs to facilitate better holding of magnet rotors to the hub. 41. Studs Step two: Place six nuts on each stud. Step three: Now fit the studs through the holes in the bearing hub. Step four: Place the rear magnet rotor on to the stud ends. Step five: Place a nut on the stud ends and then carefully tighten other studs down in a way that rear magnet rotor is attached to the hub flange back. Step six: Put the spine in a vice with the shaft in upwards position. The hub should be placed on the shaft. Avoid hammering the magnet rotor while fitting. Step seven: The hub should be carefully fastened to the shaft with a nut and split pin. Avoid over tightening the nut. Do not forget to fit a dust cover over the bearing hub end. Step eight: Now rotate the magnet rotor past a brass piece of wire. Avoid using steel wire as it is attracted to the magnets. All the magnet faces should share the same height. Step nine: Adjust the spine in the vice via using a spirit level until the magnet rotor is level. Step ten: Take the stator and fit one 8mm nut on to each support stud. Screw them down. Step eleven: Put the stator over the rear magnet rotor. Fit support studs in to spine holes. 35

36 Step twelve: Lower the stator gradually and rotate the rear magnet rotor. You need to focus on keeping the level of stator in both directions. You will be able to hear a sound as soon as the highest magnet touches the stator. Step thirteen: Use the nuts in order to raise the stator equally 1mm on all 4 studs. Step fourteen: Fit a few washers on each stud. A total of about 6 nuts and washers and 2 washers are adequate. Now it is time to fit the front magnet rotor. Step fourteen: In case, the front magnet rotor is less than 1mm from the stator, add more washers. Step fifteen: Fit more number of nuts on top as soon as the front rotor is 1mm from the stator. Tighten these in a secure manner. Electrical Parts: Block connectors are very useful for connecting the wires from the stator. Performing and crimping alternatively would be fine. You need to use solder or crimped receptacle connectors in order to connect the wires to the rectifiers. Do not overheat the rectifiers while soldering. The rectifiers need to be bolted on to the heat sink. 42. Rectifiers Make sure you keep all the connections under a weatherproof cover. 36

37 Chapter 7 Testing & connecting of PMG Check the PMG thoroughly for any faults prior to putting it in to use. It would be easier for you to rectify these faults now. However, if you practice negligence, these is no other way out than to return the unit to the workshop later. Mechanical testing You need to mount the spire in vertical position in vice. Magnet rotors can move freely. The shaft is horizontal as it is placed inside a wind generator. Check thoroughly that the wires do not touch each other. In case, they do, a short circuit is created which in turn, makes the PMG harder to turn. The rotor should spin freely. Check this by spinning the rotor & listen for any sound. No scuffing or brushing of the rotor should be heard when it turns. The rotor should spine freely for some seconds & come to a half in a slow fashion. There may be an electrical fault if it slows down in a rapid motion. This could happen even if the bearings are over tightened. Now grasp the stator with both hands. You need to push one side backward while pulling the other forward. This should be done when the rotor spins. Make sure that the stator does not touch the rotor. In case, you hear a rubbing sound, disassemble the PMG & assemble it more space between the rotor & the stator minor adjustments can rectify the problem easily. Half the rotor with one of the studs in a position of 3 o clock as shown in diagrams 43. You need to hang an object that weighs 100 grams on this stud. This will make the rotor turn clock wise. In case not, the bearing may either be go too tight or over-greased. 43. Hanging a weight on stud 37

38 How to check the balance Once the rotor & the turbine blades are balanced, you need to check the balance of the unit again. This is important as the rotor disk may not be positioned central on the PMG half. Repeat the stating test as shown in diagram 43 with all the 4 rotor studs in 3 o clock position. You must try different weights & find out the highest weight that will start the process of rotor turning. In case, more weight is required by a stud than the other, the rotor is imbalanced keep fixing small weight until you get the correct balance. Electrical testing - This is a coil connection test which is helpful in having a multimeter during the testing of PMG. You can also conduct some basic tests via basic tests via a 3 volt touch bulb as shown in diagram Electrical testing 38

39 - You need to connect a series of wines. Wire 1B will be connected to 4A, 2B to 5A & 3B to 6A. - Try setting the multimeter to 10 VAC. - You must connect the bulb or meter between the wires marked 1A & 4B. - Now rotate PMG gradually by hand for 1 revolution per second. - The meter must provide a reading of about 2 volts. - Conduct the test again with 2 different pairs of wires namely 2A & 5B, 3A & 6B. The result will be the same in both the cases. - Check the series connections thoroughly if you get low or no reading at all. In case, all the connection are proper, a coil may have been placed upside down. - Do another test if the coils are reversed first connect 4B-2 & 5B- 3A? Test between 1-A & 6B. Just a small voltage should be available. - You may experience a small voltage here. A bulb or a meter can also be used to test PMG. Just connect position & negative wires from the reelifiers in a short circuit turn the PMG. It needs to be stiff but smooth to turn. There is a fault if it trembles when you turn it. 45. Checking for reversed coil 39

40 46. DC test Connecting PMG to 12 volt battery Star & delta connection Connect the coils star for low wind speeds as mentioned above connect the coils delta for high winds & higher current out put as shown in diagram

41 You can wire a relay as shown in diagram 48. This will switch the connections from star To delta & back as desired. 48. Relay to change between STAR and DELTA 41

42 Here is another option for connecting the stator: - If you are expecting low wind speeds, use the star connection as in diagram Use a 17 AWG wire measuring 1.2mm diameter if you require higher power in higher winds to wind coils with 200 turns eas. Connect one group in delta & other in star as show in diagram Delta/star connection The cable from the PMG to the battery may be either 3-phase-AC or DC. In case, the rectifier is mounted at the wind generator, it will be DC. The cable size must be large at & volts. Use a heavy cable even if the current is only 15 amps. The recommended size is 6mm & (10 AWG) for a distance of twenty meters. The thick new of copper wire is about 3mm. Electrical safety Usually there is no risk of electric shock form a 12 volt battery. Do not run PMG at higher speed sans a battery connected. The battery consists of stored electrical energy. This energy is released in high current in case of a short circuit fault. The cable gets heated up & burn. Use a fuse or a circuit breaker on each wire that attaches to the positives terminal of battery. 42

43 Use a fuse for the wind generator & a separate one for the cable to the load. Do not make sparks near a battery. 50. Battery connection Battery charging Keep lead acid batteries in a charged condition. Do not discharge the battery too deeply. Stop using it prior to it is fully discharged. Charge the battery from a foreign source if there is a problem with wind generator. Do not charge it too hard. Use a small current for a long time. Keep a watch on the battery voltage. Case, it is lower than 11.5 volts, it is too discharged. In case it is high, it is charging too high. Use less electricity if lights are dim. 43

44 Chapter 8 Some useful additional information Usage of polyester resin Polyester is the plastic substance utilized in fiberglass work such as building car body parts, building boats etc. several things are added to this substance in order to make it function better for various processes. You may speak to your supplier and inform what the resin will be used for. Hardness Polyester resin can be hardened via using two systems. Each system utilizes two chemicals. Peroxide & cobalt are usually used for most of the fiberglass work and resin casting. The other system is used for body filler pastes. I. Cobalt It is a purple fluid you need to ask your supplier to mix the exact amount of cobalt in to the resin. Once it is mixed, store the resin in the dark to prevent it from hardening. II. Peroxide Peroxide is known to be a hazardous chemical. Hence, it is important to avoid contact with skin. You need to store peroxide in a PVC container in the dark. The storage temperature needs to be below 25 degrees. Strictly avoide mixing it with cobalt or it will explode. Focus on mixing small quantities (1-2 percent) of peroxide with resin to prevent it from over heating. Wax-free Air inhibited resin B This type of resin is ideal for get coats on boat moulds, especially where the resin will be built up in stages. Do not use this resin for PMG. Resin A will be the better choice. Using casting resin is best recommended. Thyrotrophic additive This is a special light silica powder. It is added to resin in order to give it a thicker texture. This also makes it easier to spread it with a paint brush. This powder is not required for casting resin. 44

45 Styrene monometer About 35 per cent of the resin is styrene monometer. This is specifically utilized for thinning of the resin. It results in a peculiar small. You can add more quantities of to make it more liquid. Pigment This is used to provide hue to the casting. Make sure you do not add more than 10 percent to the mixture. It is not added the casting remains transparent & all the coils are clearly visible. Fiberglass Fiberglass provides strength to the resin. It is also available in the chopped strand mat sheets. You may easily purchase chopped strands & mix them with resin. This is very beneficial for the magnet rotor castings. Add some resin to the fiberglass & press out all the air bubbles prior to adding more resin. Talcum powder This is a cheap filler and can be easily mixed with resin once the peroxide has been added. It works towards making the resin mixture affordable & thicker in texture. You can mix resin up to two times it own weight of talcum powder. The powder facilitates in minimizing the heat build-up in large resin castings. Preparation of mould Polyurethane varnish Do not use ordinary paint on moulds. Polyurethane varnish is a better option as it works towards preventing moisture from coming out of the mould prepared from clay, wood or plaster. You need to smooth the varnish off with sand paper prior to polishing it. Polish You need to polish the mould many times prior to using it for the first time. Make sure all the polish is rubbed off with a rag & leave it off for some hours repeat the process. Remember that silicone polish does not share compatibility with PVA release agent wax polish is an ideal option. 45

46 PVA release agent Paint this agent over the mould & let it dry for sometime. It forms a PVA sheet that further facilitates in separating the casting from the mould. Usage of PMG for hydro pourer The PMG can be easily utilized for charging batteries from small hydro turbines. This is a perfect option for low head, low power sites as it is efficient even for producing few watts. The best part is that it can also be utilized for higher head higher power sites due to its capability of high power outputs at high rpm. There is a risk of rust damage to the magnet rotors in humid or wet environment such as in a hydro application. The steel components must be galvanized or plated with zine. Low head sites: Here are a few instances of conditions where the PMG can function without any modification. It would require a simple impulse runner mounted on font magnet rotor. Head (meters) Flow (liters/ second) Net power (watts) PCD runner (CM) Speed (rpm) High head, high power PMG can generate higher power at higher rpm. When the speed is doubled, the output voltage in conjunction with the current is also doubled. This indicates that the PMG can easily offer 4 times as much power without any decrease in the efficiency. However, it is important to remember that the PMG is vulnerable to over heat. Hence, it would be ideal to keep the current at the same level & enjoy better efficiency. A lot will depend on usage of water for cooling. The ability of PMG S power handling is enhanced by increasing the speed. Running a wind turbine at higher speeds may be risky due to the gyroscopic forces problem on the rotors. However, this problem will not come up with hydro power as the axis of the shaft is fixed. In case, higher voltage is not needed, then the stator winding can be easily changed to provide up to 12 volts at higher speed. It will provide higher current without overheating. This is carried out via connecting the coils of each phase in parallel. The coils can also be wound with fewer turn of thicker wire. This is a better option as parallel & fdelta connections may suffer from parasitic internal currents. Avoid using the delta/ star connection for hydro power where the speed is consistent as there is no benefit. 46