Induction Motor
Design of Induction Motors
Introduction:
Induction motors are the ac motors which are employed as the prime movers in most of the industries. Such motors are widely used in industrial applications from small workshops to large industries. These motors are employed in applications such as centrifugal pumps, conveyers, compressors crushers, and drilling machines etc.
Constructional Details:
Similar to DC machines an induction motor consists of a stationary member called stator and a rotating member called rotor. However the induction motor differs from a dc machine in the following aspects. 1. Laminated stator 2. Absence of commutator 3. Uniform and small air gap 4. Practically almost constant speed
The AC induction motor comprises two electromagnetic parts:
• •
Stationary part called the stator Rotating part called the rotor
The stator and the rotor are each made up of
• •
An electric circuit, usually made of insulated copper or aluminum winding, to carry current A magnetic circuit, usually made from laminated silicon steel, to carry magnetic flux
The stator The stator is the outer stationary part of the motor, which consists of
• •
•
The outer cylindrical frame of the motor or yoke, which is made either of welded sheet steel, cast iron or cast aluminum alloy. The magnetic path, which comprises a set of slotted steel laminations called stator core pressed into the cylindrical space inside the outer frame. The magnetic path is laminated to reduce eddy currents, reducing losses and heating. A set of insulated electrical windings, which are placed inside the slots of the laminated stator. The cross-sectional area of these windings must be large enough for the power rating of the motor. For a 3-phase motor, 3 sets of windings are required, one for each
1
phase connected in either star or delta. Fig 1 shows the cross sectional view of an induction motor. Details of construction of stator are shown in Figs 4-6.
Fig 1: Stator and
Introduction:
Induction motors are the ac motors which are employed as the prime movers in most of the industries. Such motors are widely used in industrial applications from small workshops to large industries. These motors are employed in applications such as centrifugal pumps, conveyers, compressors crushers, and drilling machines etc.
Constructional Details:
Similar to DC machines an induction motor consists of a stationary member called stator and a rotating member called rotor. However the induction motor differs from a dc machine in the following aspects. 1. Laminated stator 2. Absence of commutator 3. Uniform and small air gap 4. Practically almost constant speed
The AC induction motor comprises two electromagnetic parts:
• •
Stationary part called the stator Rotating part called the rotor
The stator and the rotor are each made up of
• •
An electric circuit, usually made of insulated copper or aluminum winding, to carry current A magnetic circuit, usually made from laminated silicon steel, to carry magnetic flux
The stator The stator is the outer stationary part of the motor, which consists of
• •
•
The outer cylindrical frame of the motor or yoke, which is made either of welded sheet steel, cast iron or cast aluminum alloy. The magnetic path, which comprises a set of slotted steel laminations called stator core pressed into the cylindrical space inside the outer frame. The magnetic path is laminated to reduce eddy currents, reducing losses and heating. A set of insulated electrical windings, which are placed inside the slots of the laminated stator. The cross-sectional area of these windings must be large enough for the power rating of the motor. For a 3-phase motor, 3 sets of windings are required, one for each
1
phase connected in either star or delta. Fig 1 shows the cross sectional view of an induction motor. Details of construction of stator are shown in Figs 4-6.
Fig 1: Stator and
References: 1. 2. 3. 4. 5. 6. 7. 8. 9. A Course in Electrical Machine Design – A. K. Sawhney Design of Electrical Machines – V. N. Mittle Performance and Design of A C Machines – M G Say Design and Testing of Electrical Machines – M. V. Deshapande Electrical Machine Design Data Book – Shanmugsundaram and Palani www.google.com and related websites www.phasemotorparts.com www.wikipedia.org Krishna Vasudevan et. al. Electrical Machines II, Indian Institute of Technology, Madras 43