Rewinding of a Motor
When the motor is burnt due to short circuit or over load or some reasons, it is to be rewinded For this purpose, the following procedure is adopted:
1. To note down the name plate data of the motor i.e. phase current, voltage, R.P.M.., Type etc. Also note down the No. of poles, pitch of coils, No. of slots between two sides of coil, No. of turns in each coil ; Type of winding ; proper size of winding wire ; type of connection ; type of insulation and its size etc.
2. Taking out the burnt winding from the armature slots and to clean them well.
3. To insulate the slots with empire cloth or leatheroid paper.
4. Preparing the coils as per the previous number of turns and gauge of winding wire.
5. Inserting the coils into the slots and tightening them by bamboo strips into slots.
6. Doing the connection of winding.
7. Testing the winding and cores for
8. Insulating the ends of connection with empire sleeves.
9. Insulating the winding coils and tightening them with cotton tape and binding thread.
10. Varnishing and baking the winding. magnet.
11. After baking the other parts like rotor, front cover, back cover, centrifugal switch, condens- etc. are assembled to set the machine for final operation.
How to take out the Burnt Winding of a Stator
If only the starting winding is to be changed, then the turns of coils of starting winding are cut with hexsa blade or chisel from upper or lower side of the coil in the stator and these turns are pulled out from other side of the coil with the help of pliers turn by turn. It both the windings i.e. starting and running of the stator are to be stripped or taken out from the stator, then sometimes the stator is kept in the oven or more current is passed through the winding to burn the varnish so that the coils may become soft to remove them from the slots very easily. When they become soft, then they are cut from one side with the help of Hexsa or chisel and pulled out from other side with the help of pliers. After removing the burnt winding from the slots of the stator, they are cleaned well with the help of hexsa blade or knife.
Method of windings the Stator
(i) Hand Winding
(ii) Form Winding
(iii) Skein Winding
In all motors, first the running winding is inserted into the slots of the stator and putting the insulation layer on this winding, the starting winding coils are inserted. Thus we can say the starting winding overlap the running winding.
(i) Hand Winding.
In this method, the winding coil is inserted into the slots of the stator turn by turn by putting single turn of the coil and started from the inner coil. The process remains continued till all the coils are wound for the poles. Suppose we have to wind a 36 slots stator, then pitch 1 to 8 : 2 to 7 and 3 to 6 i.e. 1-8, 1-6, 1-4 or 7, 5, 3 will be used as shown in the Fig. below. The ends of the winding coils are kept at the bottom of the stator. The inner coil is inserted from pitch 1 to 4 as per the required number of turns. After inserting the inner coil, the next coil is inserted from I to 6 pitch and in the same direction of the inner coil. Thus all the coils will be inserted into the slots of the stator to form poles. Before starting the winding, dowel pins or wedge should be kept in the central slots so that winding coils should not come out of the slots. After completing the winding for the poles, insert the wood or fibre wedge into the slots and take out the dowel pins. The hand winding for other poles winding is shown in the following.
(ii) Form Winding.
In this winding, the proper coil is wound on the former made of wood or metal. After preparing the coils of these forms, they are put in the slots of the stator.
Steps.
To get the size of Former to prepare the proper pitched coil, a thick wire is inserted in the core of the stator at the pitch of 1 and 4 of the inner coil, leaving a margin of 6 mm on both sides for the coil as shown in.
The same method is applied to take the size of next coils leaving the distance of 5 mm between the both sides of the coils.
The wooden blocks are cut equivalent to the depth of 3/4 of the slot and as per the size of the coil to be prepared. The wooden blocks or former is assembled together and tightened with the help of nut-bolt as shown in the Fig. 7.6. This former is set in fixed stand to wind the coil conveniently.
The starting of the coil is done fromn the smallest block and coil is formed as per the requirement by winding the number of turns of the former. The coils are tied with the help of thread so that the coil should not become loose. The coil is separated from the former and inserted into the slots of the stator after using proper insulation. They are pressed in the slots and wedges are inserted on the top of the coils in the slots so that the coils in the slots should not come out of the slots and winding should remain tightened.
(iii) Skein Winding.
This is also known as type winding and mainly used to prepare the coils for starting winding. The coil is formed in such a big shape that it should be placed smoothly into the slots for a pole. In this winding the size of the coil is taken as per the original winding on the stator. This type of winding can be recognized casily as the complete coil is removed for complete one pole. If the size of the coil to be wound is not taken from the original wound coil, then it can be taken by measuring the size of a thick wire, inserting it into the slots of winding as shown in the.
सर मेरे भी मोटर वाइंडिंग करना सीखना है प्लीज मुझे सिखाएंगे सर आप मेरी करो बनेंगे क्या
ReplyDelete