Why induction motors have open slots?

Slots in motor are meant for winding around them. The lamination section surrounded by a coil forms a pole for motor. Number of such poles are decided by the windings, which in turm decide motor RPM and other characteristics.

Why do induction motors have semi closed slots?

Semi closed slots are preferred for induction motors because with their use the gap contraction factor is small giving a small value of magnetizing current. The use of semi enclosed slots results in low tooth pulsation loss and a much quieter operation as compared with that with open slots.

What is the purpose of the slots in the stator?

The stator is laminated to minimize eddy current losses in the form of heat and is divided into multiple slots. Insulated electrical coils of copper wire are inserted into the slots and arranged so that current passing through them creates an electro-magnetic field.

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What is the use of the slot in the rotor?

Wound 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 is the main function of large number of slots in induction motor?

The large number of slots in induction motor * a) Provides better overload capacity.

What happens if fifth harmonics is given to induction motor?

What happens if fifth multiples of harmonics is given to induction motor? It will rotates in reverse direction.

Why starters are required in a DC motor?

1. Why starters are required in a DC motor? … Explanation: Starting resistance of a DC shunt motor and DC compound motor is low. Well, that’s the reason why we use starters in a DC motors, in order to limit the armature current flowing through the armature and to protect machine circuitry.

How does the number of windings affect a motor?

More windings means more flux being cut and that reduces speed. Flux helps in Torque build up without which motor can’t move and forget about speed. … For AC induction or synchronous motor, same is true. More windings requires more poles and speed decreases with more number of poles.

How do you calculate the number of turns in a motor?

The number of turns in primary side is 500/10 = 50 . Number of turns in secondary side is 200/10 = 20. We can calculate the total turns ratio by calculating the voltage ratio ( primary side voltage / secondary side voltage = V1/V2). Now if you know voltage per turns then you can calculate the number of turns..

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What are the different types of slots in induction machine?

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.

What is the main motive while choosing the number of rotor slots?

Explanation: The number of rotor slots are decided for quieter operation of the machine. The number of rotor slots differs from the number of stator slots by more than the number of poles.

What is crawling in 3 phase induction?

Sometimes, squirrel cage induction motors exhibits a tendency to run at very slow speeds (as low as one-seventh of their synchronous speed). This phenomenon is called as crawling of an induction motor. This action is due to the fact that, flux wave produced by a stator winding is not purely sine wave.

What is cogging and crawling?

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 slots in DC machine?

The rotor of the type of DC motor we usually see has a lamination of slotted thin steel sheets (silicon steel plates), and the coil is inserted into the core slots. The minimum number of slots required to allow the rotor to rotate from any angle is three.

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What are the rules for selecting rotor slots in induction motor?

(The rotor winding must have the same number of poles as the stator winding.) 5. PRINCIPLE OF OPERATION When three currents, 120 electrical degrees apart, pass through the three single-phase windings in the slots of the stator core, a rotating magnetic field is developed.

What are slots in a motor?

Slots in motor are meant for winding around them. … Number of such poles are decided by the windings, which in turm decide motor RPM and other characteristics. Windings in different slots are connected to give required number of pole, and the sequence of changeover and speed of rotation.