There are two types of slots, used in ac machines; these are open type and semi-enclosed type. Semi-enclosed slots are usually preferred for induction motors. An induction motor with semi-enclosed slots has low tooth pulsation loss, less noise, less magnetising current and reduced overload capacity.
Which slots are used in the rotor of an induction motor?
01․ Which slots are used in the rotor of an induction motor? Open slots.
How many slots are there in induction motor?
The first motor has 24 stator slots and is investigated with rotor slots 20, 29 and 32 and the second motor has 36 slots and is investigated with rotor slots 28 and 44. The above-mentioned rotor slots numbers have been selected based on manufacturer’s database.
Why closed type slots are used for small induction motor?
The speed of the induction motor is inversely proportional to the load torque. In semi-closed and closed slots, the air gap between the stator and rotor is small as compared to open slots. As the air gap is small, the requirement of magnetizing current to establish the flux in the air gap is less.
Why slots on the rotor of induction motors are skewed?
The rotor or stator slot of the induction motor skewed through some angle so that the bars lie under alternate harmonic poles of the same polarity or other words, bars must be skewed through two pitches. The main purpose of skewing is to reduce the magnetic logging between the starter and the rotor.
What is the use of the slot in the rotor?
The rotor is a cylindrical core made of steel lamination with slots to hold the wires for its 3-phase windings which are evenly spaced at 120 electrical degrees apart and connected in a ‘Y’ configuration.
What are motor slots?
A slot represents the number of coils of fixed stators. Three-phase motor has a multiple of 3 slots.
What are the types of slot used in IM?
Stator slots: in general two types of stator slots are employed in induction motors viz, open clots and semiclosed slots. Operating performance of the induction motors depends upon the shape of the slots and hence it is important to select suitable slot for the stator slots.
How many slots does a motor have?
A basic single-phase motor usually has four slots that contain two pairs of coil windings, each offset by 90 degrees; a basic three-phase motor has six slots with three pairs of coil windings, each pair offset by 120 degrees.
Which type of slots are generally used in induction motors Mcq?
Small size induction motors use semiclosed slots, so as to reduce the effective gap length between stator and rotor. 2.
What is regenerative braking in 3 phase induction?
Regenerative Braking of Induction Motor
When the speed of the motor is more than the synchronous speed, relative speed between the motor conductors and air gap rotating field reverses, as a result the phase angle because greater than 90o and the power flow reverse and thus regenerative braking takes place.
Can closed slots are preferred for small machines?
Explanation: Closed slots are preferred for small machines. It is because the reluctance of the air gap is not large owing to absence of slot openings.
Why is an induction motor called a rotating transformer?
In induction motor, rotor is short circuted, there is no physical contact between stator and rotor. rotor is made to rotate due to induce effect of stator..which is similar to transformer operating principle where primary and secondary magnetically coupled. thats why it is called rotating transformer.
What is crawling and cogging?
October 27, 2020 February 24, 2012 by Electrical4U. The important characteristics normally shown by a squirrel cage induction motors are crawling and cogging. These characteristics are the result of improper functioning of the motor that means either motor is running at very slow speed or it is not taking the load.
What is slip in an induction motor?
“Slip” in an AC induction motor is defined as:
As the speed of the rotor drops below the stator speed, or synchronous speed, the rotation rate of the magnetic field in the rotor increases, inducing more current in the rotor’s windings and creating more torque. Slip is required to produce torque.