Why rotor slots in induction motor skewed Rotor (electric)

Why rotor slots in induction motor skewed. Why rotor of squirrel cage induction motor is skewed

Development quickly included more useful applications such as Moritz Hermann Jacobi 's motor that could lift 10 to 12 pounds with a speed of one foot per second, about 15 watts of mechanical power in Developments of this design became commercially important.

In turn these currents lengthwise in the conductors react with the magnetic field of the motor to produce force acting at a tangent orthogonal to the rotor, resulting in torque to turn the shaft. The shape and depth of the rotor bars can be used to vary the speed-torque characteristics of the induction motor.

Use in synchronous motors[ edit ] A synchronous motor may have a squirrel-cage winding embedded in its rotor, used to increase the motor starting torque and so decrease the time to accelerate to synchronous speed.

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The end are then connected using conductive rings forming a …cage like for a squirrel. When the number of rotor and stator poles are equal in the motor and if these rotor poles have opposite polarity with respect to the stator poles magnetic locking occurs.

The motors bearings can be cleaned and re why rotor slots in induction motor skewed or …if sealed bearings that can be changed out for new ones. The motor runs as a cage induction motor. The rotor will stay onbetter because it is not as slippery. An external direct current DC source is connected to the concentrically mounted slip rings with brushes running along the rings.

Would you like to make it the primary and merge this question into it? The wound rotor slip ring motor is similar in construction but the bars are replaced by copper windings, similar to those in the stator.

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The only preventive maintenance that can be done to electric motors by maintenance personnel is to disassemble the motor. The name is derived from the similarity between this rings-and-bars winding and a squirrel cage.

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The solid core of the rotor is built with stacks of electrical steel laminations. For this to work the motor must either be connected to a grid supply or an arrangement of capacitors to provide excitation current. When rotor speed increases, the slip decreases. Both have 3 a phase stator winding, the squirrel cage has a rotor with bars arranged around it's periphery, these bars are joined at both ends by a continuous ring.

As the slip increases, skin effect starts to reduce the effective depth and increases the resistance, resulting in reduced efficiency but still maintaining torque. They are star connected and the three ends are brought out to slip rings which allow an electrical connection to be made to the outside world.

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In order to avoid this problem, the rotor slots housing the conductors are skewed by an angle of 5 degrees over the surface. There are two designs for the rotor in an induction motor: At standstill, the revolving magnetic field passes the rotor bars at a high rate, inducing line-frequency current into the rotor bars.

Construction of squirrel cage induction motor explained - squirrel cage rotor

Rotor slip provides necessary induction of rotor currents for motor torque, which is in proportion to slip. When the rotor is turning at the same speed as the stator's revolving magnetic field, no current is induced into the squirrel-cage windings and the windings will have no further effect on the operation of the synchronous motor at steady-state.

Dirt accumulations around coil wiring insulation is the biggest cause of motor failure. As the motor accelerates, the slip frequency decreases and induced current flows at greater depths in the winding.

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As the rotor gains speed the resistance is taken out of circuit and the slip rings shorted together. The coil wires need cooling air moving across them. Large machines may only have amortisseur bars in the individual pole faces, not interconnected between poles.


In some motors, there is an extension at the non-driving end for speed sensors or other electronic controls. What is cogging in squirrel cage induction motor? DC current is also supplied through brushless excitation from a rectifier mounted on the machine shaft that converts alternating current to direct current. Because the magnetic field in the rotor is alternating with time, the core uses construction similar to a transformer core to reduce core energy losses.

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This will cause the motor to generate power after building up its residual magnetism. The iron core serves to carry the magnetic field through the rotor conductors. Direct current DCfrom an external exciter or from a diode bridge mounted on the rotor shaft, produces a magnetic field and energizes the rotating field windings and alternating current energizes the armature windings simultaneously.

History[ edit ] Galileo Ferraris described an induction machine with a two-phase stator winding and a solid copper cylindrical armature in Increasing the slip increases induced motor current, which in turn increases rotor current, resulting in a higher torque for increase load demands.

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