Understanding electric motor windings!
It’s a pleasure to watch the fabrication process of windings in the factories. What you see here is a fully automatic winding process. The windings take in electric current and create a rotating magnetic field out of it. This RMF is responsible for the motor’s rotation. You might be curious about how this magnetic field rotates even when the windings are stationary? Let’s unveil its working, come along!
Hello everyone, I am Niko and, in this instructables I will show you, how to rewind and renew an old three phase electric motor.
If you are searching for rewinding of one phase motor you can find it here.
In this instructables, I am going to make a step forward. In next steps I will show you how to analyze winding motors, disassemble motor, remove bearings, calculate new winding, rewind motor, reassemble it with new bearings and test motor. Rewinding is a very long process. It took about two days to rewind it, replace all old parts and reassemble it.
I got this motor at my university.
Three phase asynchronous motor is the most common used motor in the world. It has very good efficiency and low manufacture and maintenance costs. Two main parts of motor are rotor and stator. Rotor is usually made as a squirrel-cage, and it is inserted in stators hole. Stator is made out of iron core and winding.
Stator is used to generate magnetic field. 3 phases generates rotation magnetic field so we don't need capacitor on three phase motor. Rotation magnetic field "cut" squirrel-cage, where it induces voltage. Because cage is short-circuited, voltage generates flow of electric current. Current in magnetic field generates force.
Because magnetic field must rotate faster than rotor to induce voltage in rotor. That's why motor speed is a little bit less then magnetic field speed ((3000 rpm [Magnetic field] -- 2810 rpm [Electric motor])). That's why we call them Three phase ASYNCHRONOUS electric motor.
Open the cover of conduit box.
Before measuring remove all connections in conduction box. Measure resistance for each winding, resistance between two different winding and resistance between winding and motors frame.
Resistances of three winding should be the same (+/- 5%). Resistance between two winding and winding - frame should be more than 1,5 Mohm.
You can detect burned winding motors by unique smell (smells like burned lacquer).
Take a few pictures of motor. Mark spots between first cover and stator and second cower and stator (we will need these marked points at motors assemble).
Remove covers from motor. Usually they are attached to the stator by long screws. If you cant separate cover and stator you can use rubber hammer. Gently hit cover and try to rotate it. If that wont work, heat it.
Remove rotor from stator. You can gently hit the rotors axis with a rubber hammer.
Remove ventilator from rotors axis. I had metal ventilator so i heated it up. I separated it very easily from axis.
Remove clamp and safety ring if you have one. Then remove second cover.
Use puller to remove bearings on both sides. You must be careful because you can easily damage the axis of rotor.
First you need to cut old winding from stator. For this job use hammer and chisels. Try not to damage stators lamellas.
Remove connections and conduit box from stator. In the next step you will need to heat up old coils, and conduit box must be empty.
Heat up winding with flame torch to burn out the rest of lacquer.
If you burned old lacquer you should be able to push remaining winding out of stators gaps.
Sandblasting is a process where sand hits the surface of the workpiece with very high speed and slightly damages it.
You can easily remove old color form motor with sandblasting. While sandblasting you need to be careful, that you don't damage the surface too much, especially the edges of cowers.
The color must withstand at least 100 degrees Celsius. Make sure you don't paint inscription board.
You can find all information about type of old winding in "winding head". Winding head is part of winding where all connections are made.
By the winding head (Type of winding), number of wires in each gap and thickness of the wire you can rewind new winding motors without doing calculations in the next step.
New winding of motor depends of stators package (dimensions of iron core). For better presentation i made 3D model of my stators package.
You need to measure following things:
Length of stators package: lp= 87mm;
External diameter of statros package: Dv= 128mm;
Inner diameter of stators package: D= 75.5mm;
Number of stators gaps: Z= 24;
Number of pole pairs depends on nominal frequencies and rotation speed of magnetic field. You can get rotation speed of magnetic field by rotating motors speed (2810) to closest value (3000, 1500, 1000, 750...).
I calculated that my motor has 2 pole pairs and it generates magnetic field as you can see on the upper picture.
Pole surface is marked red on picture two. One pole surface is exactly half surface of stator, that is because i have 2 pole motor.
Because iron core of stator is not made out of pure iron we need to calculate real package length. You get iron filling factor from upper table. It depends on type of isolation.
I chose type of winding based on my motors specifications. In winding books there is a lot of different types of winding diagrams. Each one is drowning for different amount of pole pairs.
I took winding on the picture from winding book. My new winding was three phase single layer concentric winding.
Understanding electric motor windings!
It’s a pleasure to watch the fabrication process of windings in the factories. What you see here is a fully automatic winding process. The windings take in electric current and create a rotating magnetic field out of it. This RMF is responsible for the motor’s rotation. You might be curious about how this magnetic field rotates even when the windings are stationary? Let’s unveil its working, come along!
Hello everyone, I am Niko and, in this instructables I will show you, how to rewind and renew an old three phase electric motor.
If you are searching for rewinding of one phase motor you can find it here.
In this instructables, I am going to make a step forward. In next steps I will show you how to analyze winding motors, disassemble motor, remove bearings, calculate new winding, rewind motor, reassemble it with new bearings and test motor. Rewinding is a very long process. It took about two days to rewind it, replace all old parts and reassemble it.
I got this motor at my university.
Three phase asynchronous motor is the most common used motor in the world. It has very good efficiency and low manufacture and maintenance costs. Two main parts of motor are rotor and stator. Rotor is usually made as a squirrel-cage, and it is inserted in stators hole. Stator is made out of iron core and winding.
Stator is used to generate magnetic field. 3 phases generates rotation magnetic field so we don't need capacitor on three phase motor. Rotation magnetic field "cut" squirrel-cage, where it induces voltage. Because cage is short-circuited, voltage generates flow of electric current. Current in magnetic field generates force.
Because magnetic field must rotate faster than rotor to induce voltage in rotor. That's why motor speed is a little bit less then magnetic field speed ((3000 rpm [Magnetic field] -- 2810 rpm [Electric motor])). That's why we call them Three phase ASYNCHRONOUS electric motor.
Open the cover of conduit box.
Before measuring remove all connections in conduction box. Measure resistance for each winding, resistance between two different winding and resistance between winding and motors frame.
Resistances of three winding should be the same (+/- 5%). Resistance between two winding and winding - frame should be more than 1,5 Mohm.
You can detect burned winding motors by unique smell (smells like burned lacquer).
Take a few pictures of motor. Mark spots between first cover and stator and second cower and stator (we will need these marked points at motors assemble).
Remove covers from motor. Usually they are attached to the stator by long screws. If you cant separate cover and stator you can use rubber hammer. Gently hit cover and try to rotate it. If that wont work, heat it.
Remove rotor from stator. You can gently hit the rotors axis with a rubber hammer.
Remove ventilator from rotors axis. I had metal ventilator so i heated it up. I separated it very easily from axis.
Remove clamp and safety ring if you have one. Then remove second cover.
Use puller to remove bearings on both sides. You must be careful because you can easily damage the axis of rotor.
First you need to cut old winding from stator. For this job use hammer and chisels. Try not to damage stators lamellas.
Remove connections and conduit box from stator. In the next step you will need to heat up old coils, and conduit box must be empty.
Heat up winding with flame torch to burn out the rest of lacquer.
If you burned old lacquer you should be able to push remaining winding out of stators gaps.
Sandblasting is a process where sand hits the surface of the workpiece with very high speed and slightly damages it.
You can easily remove old color form motor with sandblasting. While sandblasting you need to be careful, that you don't damage the surface too much, especially the edges of cowers.
The color must withstand at least 100 degrees Celsius. Make sure you don't paint inscription board.
You can find all information about type of old winding in "winding head". Winding head is part of winding where all connections are made.
By the winding head (Type of winding), number of wires in each gap and thickness of the wire you can rewind new winding motors without doing calculations in the next step.
New winding of motor depends of stators package (dimensions of iron core). For better presentation i made 3D model of my stators package.
You need to measure following things:
Length of stators package: lp= 87mm;
External diameter of statros package: Dv= 128mm;
Inner diameter of stators package: D= 75.5mm;
Number of stators gaps: Z= 24;
Number of pole pairs depends on nominal frequencies and rotation speed of magnetic field. You can get rotation speed of magnetic field by rotating motors speed (2810) to closest value (3000, 1500, 1000, 750...).
I calculated that my motor has 2 pole pairs and it generates magnetic field as you can see on the upper picture.
Pole surface is marked red on picture two. One pole surface is exactly half surface of stator, that is because i have 2 pole motor.
Because iron core of stator is not made out of pure iron we need to calculate real package length. You get iron filling factor from upper table. It depends on type of isolation.
I chose type of winding based on my motors specifications. In winding books there is a lot of different types of winding diagrams. Each one is drowning for different amount of pole pairs.
I took winding on the picture from winding book. My new winding was three phase single layer concentric winding.
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