Ever wondered why slip is so important in induction machine?
(If you do not know, in case: slip is a measure of speed difference between stator and rotor magnetic field in induction machine.) When stator coil is energized in induction machine, it produces a magnetic field. If the energizing force i.e. voltage or current is rotating in nature, generated stator magnetic field is rotating in nature as well.
When this stator magnetic field starts rotating around rotor, it cuts the rotor coil (or the conductor bars embedded in rotor). Therefore, the rotor experiences a changing
magnetic field. This changing magnetic field produces another changing magnetic field in rotor, as known from electromagnetic principles like F=B*i*L*sin(theta). This two magnetic field is opposite in nature, making them feel attraction towards each other.
When rotor field got strong enough, usually in few seconds, it starts trying to catch the stator field. So the rotor itself starts to rotate around its axis. As the rotor field gets closer to stator field, its attraction towards stator suddenly reduces, which can be verified using F=B*i*L*sin(&Theta). So rotor fields weakens and it rotor itself loses its speed. As rotor gets slow, rotor field starts feeling stronger attraction again and gains energy to rotate faster (rotor fields move forward). So, it becomes a dilemma for the rotor.
This is what the slip is.
But what is the significance of this slip?
The slip PRODUCES the starting torque, can you see how? I have already described it in the above paragraph. Read the last paragraph again and see how the rotor gains energy to move forward.
Do you see the slip can never be zero? As it drives the rotor in induction machine, if it (slip) becomes zero i.e. rotor field catches the stator field, force between stator and rotor becomes zero and rotor stops rotating. Which will eventually produces attraction between stator and rotor again and slip will be in effect as well.
You can read details of induction motor working principles, in simple words here:
http://get-a-solution.blogspot.com/2010/03/basic-principle-of-induction.html
If you want to know how DC breaking works, read the following posts:
http://get-a-solution.blogspot.com/2010/04/electrical-braking-theory-reason-of-dc.html
and http://get-a-solution.blogspot.com/2010/05/regenerative-braking-of-electrical.html
(If you do not know, in case: slip is a measure of speed difference between stator and rotor magnetic field in induction machine.) When stator coil is energized in induction machine, it produces a magnetic field. If the energizing force i.e. voltage or current is rotating in nature, generated stator magnetic field is rotating in nature as well.
When this stator magnetic field starts rotating around rotor, it cuts the rotor coil (or the conductor bars embedded in rotor). Therefore, the rotor experiences a changing
magnetic field. This changing magnetic field produces another changing magnetic field in rotor, as known from electromagnetic principles like F=B*i*L*sin(theta). This two magnetic field is opposite in nature, making them feel attraction towards each other.
When rotor field got strong enough, usually in few seconds, it starts trying to catch the stator field. So the rotor itself starts to rotate around its axis. As the rotor field gets closer to stator field, its attraction towards stator suddenly reduces, which can be verified using F=B*i*L*sin(&Theta). So rotor fields weakens and it rotor itself loses its speed. As rotor gets slow, rotor field starts feeling stronger attraction again and gains energy to rotate faster (rotor fields move forward). So, it becomes a dilemma for the rotor.
This is what the slip is.
But what is the significance of this slip?
The slip PRODUCES the starting torque, can you see how? I have already described it in the above paragraph. Read the last paragraph again and see how the rotor gains energy to move forward.
Do you see the slip can never be zero? As it drives the rotor in induction machine, if it (slip) becomes zero i.e. rotor field catches the stator field, force between stator and rotor becomes zero and rotor stops rotating. Which will eventually produces attraction between stator and rotor again and slip will be in effect as well.
You can read details of induction motor working principles, in simple words here:
http://get-a-solution.blogspot.com/2010/03/basic-principle-of-induction.html
If you want to know how DC breaking works, read the following posts:
http://get-a-solution.blogspot.com/2010/04/electrical-braking-theory-reason-of-dc.html
and http://get-a-solution.blogspot.com/2010/05/regenerative-braking-of-electrical.html
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